Show us your square wave

[Electro Fan]

Just checking to see if any Agilent, Tektronix, Rigol, or other square wave (function) generator users can show us your highest frequency square wave that looks like a strong square wave?  Would be especially interested to see the best high frequency square wave from any Rigol DG1032Z and DG1062Z users, but all makes and models welcome.  Thanks, EF

- kind of curious to see what is the lowest price device is that can produce a really good looking square wave at 1, 5, 10, 20, and 30 MHz? 

[katzohki]

Current stuff or older stuff too? I'm picking up a couple older function gens in about a week.

[Electro Fan]

Current stuff or older stuff too? I'm picking up a couple older function gens in about a week.

all examples welcome 

[katzohki]

BK 4011A:

BNC directly to scope input @ ~5MHz

[0xdeadbeef]

Rigol DG2021A on Hameg HMO2024
5V Amplitude, 2.5V Offset, 50% DC, High Z and 50Ohm in/out, BNC
Note: 25MHz maximum and for some reason selecting 50Ohm limits the amplitude to 2.5V over 10MHz.

[rob77]

how would you know it's really a perfect square wave without a scope with infinite bandwidth ? 

[tautech]

Just checking to see if any Agilent, Tektronix, Rigol, or other square wave (function) generator users can show us your highest frequency square wave that looks like a strong square wave?  Would be especially interested to see the best high frequency square wave from any Rigol DG1032Z and DG1062Z users, but all makes and models welcome.  Thanks, EF

- kind of curious to see what is the lowest price device is that can produce a really good looking square wave at 1, 5, 10, 20, and 30 MHz?

There are quite a few variables as to how these could be interpreted.
It's all very well to ask for sample waveforms, but you will get so many results that aren't worth a knob of goat shit unless you specify how the FG is connected to the scope.
50 Ohm coupling ?
Hi Z coupling?
Probe connection?
BNC Cable connection?

Most AWG's specify a square wave to only a portion of their max sine wave capabiliy to remain within their risetime specs.

This is what you need to see:
(Siglent SDS2304 internal AWG 1MHz 50 Ohm source & termination, Coax connection)

[c4757p]

50 Ohm coupling ?

Good point. Nobody should even bother posting here unless they've used a properly terminated connection. Otherwise, you're not seeing the square wave, you're seeing the LC characteristics of the cable.

You might get a decent signal if you stick a high-bandwidth scope probe right into the BNC output of the function generator, as well, though that's only if the function generator's output amp is rather close to the back side of the jack.

[katzohki]

Proper termination? Oh boy, you really are asking for the moon! 

[jpb]

My scope doesn't like anything above 5Vrms for the 50 ohm input so I've produced two square waves at 4.5Vrms nominal at 20MHz and 30MHz
for an Agilent 33522A. NB the rise time is slow (officially 8.7nsecs) but the curves are smooth.

It is interesting to note how inaccurate the peak-to-peak is, it should be 9V for a perfect square. The rms is obviously out as the waves are far from square at these frequencies.

The peak-to-peak was much closer down at 1V or less.

Note, I've not used averaging but I did have equivalent time sampling turned on and the waveforms are very smooth still because the jitter is very small on the Agilent.

[0xdeadbeef]

100GS? Jesus Christ!

[Alex Eisenhut]

100 MHz into 1S1 50 ohm input.

[T3sl4co1l]

100GS with "EQU" at the top (I assume indicating equivalent time sampling).

It's not a square wave exactly, but it is pushing the instrument BW:



350MHz TDS460, coaxial connection, internally terminated.  (150MS instrument, so again, the 10GS is "ET".)  Ch.2 is a 10x probe (also more-or-less coaxially connected), with a shorter cable hence the time difference.

Tim

[joeqsmith]

Just checking to see if any Agilent, Tektronix, Rigol, or other square wave (function) generator users can show us your highest frequency square wave that looks like a strong square wave?  Would be especially interested to see the best high frequency square wave from any Rigol DG1032Z and DG1062Z users, but all makes and models welcome.  Thanks, EF

- kind of curious to see what is the lowest price device is that can produce a really good looking square wave at 1, 5, 10, 20, and 30 MHz?

Hummm..... Not really sure what you are looking for but I can't let that 1nS rise fall time be the record holder. 

So, here's my vintage 90's LeCroy DSO looking at one leg from my 70's HP8640B RF generator with an LVDS driver.     

[Rupunzell]

Tektronix 2101 Generator, Tektronix 7104 & 7A29 & 7B10.

Tek 7A29 is 50 ohm input.
Gore coax with APC 3.5 connectors and APC-3.5 to BNC adapters between the Tek 2101 & 7A29 input.

Maybe I'll dig out the Tektronix Type 106.


Bernice

[joeqsmith]

If 370ps was not fast enough....   Vintage HP8660 with PECL buffer. 

[mazurov]

Tektronix 7000-series with 7S12 plugin. S-52 pulser into S-6 head.

[Jay_Diddy_B]

Hi,

Here is a Tektronix 11801 scope mainframe using a SD26 sampling head 17.5 ps risetime showing the output pulse from a SD24 TDR head. The combined risetime of the pulse generator and the scope is 26ps



Light travels 7.8mm in 26ps !!



Regards,

Jay_Diddy_B

[marshallh]

[pickle9000]

I'm kinda liking this thread.

[LabSpokane]

Am I the only one baffled by the question?  Are we trying to prove Fourier here? That said, I plan to win the race with my 18000 ps rise time.  More is better, right...?

Agilent MSOX2024 with the internal function generator. 

(And thanks for the thread.  It finally got me off my ass to get the scope plugged into BenchVue. )

[Rupunzell]

I'm waiting for images from the Hypress PSP-1000 or PSP-750.

Point of of this race when the initial question was "affordable" square wave generators ?
More often than not, web forums discussion become a battle or race to see who can prove they are at the top of their ...


Bernice

[mazurov]

Define "affordable". My setup can be had for less than $100, At present, I'm looking to buy a rig similar to JDBs and for 50 GHz bw configuration I'm hoping to spend ~$300 shipped.

[Wuerstchenhund]

100GS? Jesus Christ!

It's RIS which is a form of Equivalent Time Sampling, not real-time sampling. It's only 2GSa/s (1GSa/s with all channels active) in real-time mode for the WaveJet.

[Alex Eisenhut]

I'm waiting for images from the Hypress PSP-1000 or PSP-750.

Point of of this race when the initial question was "affordable" square wave generators ?

The clock generator from a PC can be sawn off the motherboard.

[LaurentR]

DG1022 at full blast: 5MHz square 
Serious edge rate: 22ns rise time. Spec says <20ns. Almost...

5Vrms, 50Ohms throughout. Captured by a DS1074Z.

[tautech]

DG1022 at full blast: 5MHz square 
Serious edge rate: 22ns rise time. Spec says <20ns. Almost...

5Vrms, 50Ohms throughout. Captured by a DS1074Z.

Is that a bit of jitter we see? 

[Electro Fan]

Hi EEVers,

Thanks for all the square wave examples.

Just to confirm, there were a few motivations/intentions embedded in the original post:

1. Best quality achievable at given frequencies - what is the best looking square wave that can be produced at various frequencies (such as 1, 5, 10, 20, and 30 MHz)?  This is independent of the price of the equipment used.  It's interesting to see what types of generators, test leads, and scopes are out there and what they can produce.  Some generators are perhaps optimized for square waves and perhaps pulses, others might be more multi-function.  Again, just looking to see what equipment can produce a good looking square wave.  (A bit off topic but it appeared that some scopes produce especially nice text and numeric readouts that make the values being measured very clear at a glance - 0xdeadbeef's Hameg HMO2024 looked pretty nice.)

2. Definition of quality - this is related to item 1 but beyond the generators, test leads, and scopes involved is the notion of "what constitutes a good looking square wave?"  No doubt rise time is a key attribute but perhaps there are other attributes to consider (such as how much ringing, etc?).

3. Cost to achieve quality - given that various setups produce various levels of square wave quality, which generators (and test leads) are the most cost-effective for each frequency (1, 5, 10, 20, and 30 MHz)?

(PS, What inspired all this was some recent testing of a couple generators; I was curious to see what "par for the course" is at the various frequencies.)  Thanks and please feel free to keep posting square wave images and any related info along with questions and comments, of course.  EF

[tautech]

Now I've got some time to post what the OP wanted to see. 
From Siglent SDG1010 10 MHz AWG.
3 V p-p & 50 Ohm source.
Captured with Siglent SDS2304 using internal 50 Ohm termination, connection 1 M RG58C/U BNC to BNC.

First image as posted previously, 1 MHz from internal SDS2304 AWG. 4 V p-p.


SDG1010 1 MHz


SDG1010 5 MHz


SDG1010 10 MHz


EDIT
SDG1010 Risetime @ 10 MHz = 6.38 nS mean, Std Dev 156 ps over 13000 counts.
From on-screen measurements SDS2304

[tboy]

Rigol DS2072 hacked to DS2202
Rigol DG1032Z
15MHz into 50ohms

[Paul Moir]

Ok, back to what the OP didn't ask for.  Lets get this back on track. 

HP 3312A at 5MHz, under the spec'd 20ns rise time at 3MHz.  Definitely squarish as advertized. 



But things start to get pretty curvy out at 13MHz:  Had the bandwidth limiter on!  Not so bad at 13MHz:



Scope is a Tek 465 at 10ns/div using a BNC T and terminator. 

[rf-loop]

Rigol DS2072 hacked to DS2202
Rigol DG1032Z
15MHz into 50ohms

Why it was stopped before image?
Turn normal sample mode, turn persistence on (example 1-5sec)
Keep it running and take image.

[jpb]

100GS?

It is on equivalent time sampling on a WaveJet so the time resolution is down to that but the points are obtained from multiple waves. The fact that the waves are still smooth is an indication (I think) that there is very little jitter.

[Wuerstchenhund]

It is on equivalent time sampling on a WaveJet so the time resolution is down to that but the points are obtained from multiple waves. The fact that the waves are still smooth is an indication (I think) that there is very little jitter.

Not really. You simply can't assess jitter in RIS mode. RIS is only sensible for signals that are truly repetitive.

LeCroy has published a good paper on RIS:
http://cdn.teledynelecroy.com/files/whitepapers/wp_ris_102203.pdf

"[...] In order to use RIS, the application must meet the following requirements:
1. The waveform must be repetitive.
2. The trigger event must be identical for every sweep.

Repetition is the key. RIS makes the assumption that every waveform segment that is acquired is the exact same analog waveform. Furthermore, it assumes that this same analog waveform is triggered at that exact same place in the waveform on every acquisition. The only difference assumed is that the sampling phase (where the trigger occurs with relation to samples) is changing.

These restrictions on repetition are serious. It means that the waveform must be repetitive, the trigger must be stable, and no non-repetitive nature of a waveform, like jitter etc. can be measured properly in this mode. Failure to honor these restrictions results in severely distorted waveforms with no usefulness whatsoever and erroneous measurements."

What this means is that what you see on the scope could well be complete garbage unless you're sure your waveform is sufficiently repetitive.

For this exercise I would not use RIS or any other ETS variant. The 2GSa/s sample rate of your WaveJet should be more than good enough for the displayed waveform (or probably any waveform that is within the scope's analog bandwidth).

[joeqsmith]

Ok, back to what the OP didn't ask for.  Lets get this back on track. 

Agree.   

You guys with the old Teks < 30ps       Good job!      

Home made ARB I built for a home project back in the 80s.    It can record and playback.  No DSO at home back then....     6800 based, used some 3055s for the output.  PCB for the output driver but wire wrap for the controls, and it's got a lot of pins.         


Putting out some random data......   

[c4757p]

DG1022 at full blast: 5MHz square 
Serious edge rate: 22ns rise time. Spec says <20ns. Almost...

5Vrms, 50Ohms throughout. Captured by a DS1074Z.

Is that a bit of jitter we see? 

Yes, in the DG1022 output. Its jitter is just embarrassing. Whoever designed it has no clue how to generate a variable-frequency signal.

That looks like what I see from my DG1022 at higher frequencies on any scope.

[jpb]

Here is an historic one from a Levell TG150D that I've just been given and hope to restore (it is very noisy at present).

The maximum it can do is 2.5V and 160kHz (nominal 150kHz but the dial goes a bit higher).

EDIT:
I realise that I had the attenuated set for 20dB so I've added a shot with it off below.

[Wuerstchenhund]

The following screen shots are for a Rigol DG1062z which is probably closer to what the OP was looking for.

The images show the DG1062z in square wave mode at 1/2/3/5/10/20/25MHz at 2.5Vpp and with 50% duty cycle. The output was 50ohms terminated into a known good 30cm RG-58C/U cable.

The scope is a LeCroy WavePro 7300A (3GHz bandwidth, 20GSa/s, 48Mpts), the input is set to 50ohms and full bandwidth mode.

The DG1062z's square wave looks ok until 20MHz but above that it's pretty poor (closer to a sine).

[EV]

Tek R7103, S4 with sampling head extender connected straight to Tek 284 pulse generator.

[Howardlong]

Tek R7103, S4 with sampling head extender connected straight to Tek 284 pulse generator.

Definitely a bit of jitter there 

[rf-loop]

The following screen shots are for a Rigol DG1062z which is probably closer to what the OP was looking for.

The images show the DG1062z in square wave mode at 1/2/3/5/10/20/25MHz at 2.5Vpp and with 50% duty cycle. The output was 50ohms terminated into a known good 30cm RG-58C/U cable.

The scope is a LeCroy WavePro 7300A (3GHz bandwidth, 20GSa/s, 48Mpts), the input is set to 50ohms and full bandwidth mode.

The DG1062z's square wave looks ok until 20MHz but above that it's pretty poor (closer to a sine).

Here Siglent SDG5082 
Some amount different what Rigol DG1062Z
Signal from SDG, around 60cm cable and scope input set for 50ohm.

[rx8pilot]

The following screen shots are for a Rigol DG1062z which is probably closer to what the OP was looking for.

The images show the DG1062z in square wave mode at 1/2/3/5/10/20/25MHz at 2.5Vpp and with 50% duty cycle. The output was 50ohms terminated into a known good 30cm RG-58C/U cable.

The scope is a LeCroy WavePro 7300A (3GHz bandwidth, 20GSa/s, 48Mpts), the input is set to 50ohms and full bandwidth mode.

The DG1062z's square wave looks ok until 20MHz but above that it's pretty poor (closer to a sine).

That seems to be a very telling test. My question is how do you tell the difference between the scope limitations and the SG limitations and the test environment limitations (cables, probes, etc).

I would hope that a 3Ghz, 20GS/s scope is not the limitation here but I am not sure how to know. When I see top and bottom ringing, what are the possible origins of that error?

[nuno]

Tek R7103, S4 with sampling head extender connected straight to Tek 284 pulse generator.

Uooouu, we can even see the electrons, lol

[BloodyCactus]

I can take square wave pics on my 1032Z tonight after work, looks good at low freqs, but at its max which is 15mhz I think, its really a sine wave which is really disappointing.

[katzohki]

Quote from: rx8pilot on Today at 05:43:29 AM

That seems to be a very telling test. My question is how do you tell the difference between the scope limitations and the SG limitations and the test environment limitations (cables, probes, etc).

I would hope that a 3Ghz, 20GS/s scope is not the limitation here but I am not sure how to know. When I see top and bottom ringing, what are the possible origins of that error?

My guess is that the ringing seen on my and many other scope shots is the capacitance in probes, cables, scope input etc and the lack of 50 ohm termination. The rise time / slope of the signals at high frequencies is probably tied to limitation of the function generators.

Maybe someone can post a picture of terminated vs unterminated to illustrate the difference. That or I will after I pick up my 2 new FGs in a week.

[Wuerstchenhund]

That seems to be a very telling test. My question is how do you tell the difference between the scope limitations and the SG limitations and the test environment limitations (cables, probes, etc).

I would hope that a 3Ghz, 20GS/s scope is not the limitation here but I am not sure how to know.

I'm pretty sure the scope isn't a limiting factor here. We're talking about square waves of 25MHz and below and 3GHz (120 times the frequency of the 1st harmonic) is more than enough bandwidth to capture all relevant frequency components. The scope has also been calibrated pretty recently.

The cable has been tested a while ago up to 600MHz. I also did a quick comparison with a brand new 1m RG-58 cable and the results are the same (both cables are high quality cables and not some cheap chop suey stuff). This aside, some time ago I also used the AWG with my other scope (LeCroy WaveRunner 64Xi 600MHz 10GSa/s) and the 25MHz square wave was as shit then as it is today.

So I'm pretty sure that the measurements are valid.

I guess the reason for the bad results at 25MHz is in the slow edges of the DG1062z.

When I see top and bottom ringing, what are the possible origins of that error?

Difficult to say but I'm sure it's from the AWG. Maybe there's a mis-match with the internal termination (I'll see if I can check with external termination tomorrow).

I also noticed that at higher frequencies the DG1062z shows some slight jitter.

[0xdeadbeef]

Honestly I think the bad ringing in the plateau between the edges mainly comes from the signal generators.
The small overshoot and ringing directly at the (rising) edge even hints towards a lack of capacitance.
Besides, I posted HiZ vs. 50Ohm screenshots. There are differences but they are not overwhelming.

[Wuerstchenhund]

Here Siglent SDG5082 
Some amount different what Rigol DG1062Z
Signal from SDG, around 60cm cable and scope input set for 50ohm.

Interesting, it seems the SDG5000 has much shorter edges than the DG1062z (which is a bit disappointing really, considering the Rigol's price tag).

Nice scope. HP 54500 Series I guess?

[nuno]

This is from the DS1104Z-S. Not famous. Coax from sgen output to a T on the scope input and a 50 Ohm terminator (except for the amplitude doesn't actually make any relevant difference, terminated or not).

[rf-loop]

Nice scope. HP 54500 Series I guess?

Yes, 20 years young workhorse, Hewlett-Packard  54522A.

[rx8pilot]

This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.

On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.

[jadew]

I agree, it's an interesting thread, but keep in mind that your cables probably suck so the only information we could rely on is the rising time. Any ringing you see could be caused by the cable or the cable + dummy load (unless you can test them with a different instrument).

I remember managing to get some extremely clean square waves out of my wave gen - that's not the case anymore because I don't remember which cable/dummy load I've been using

Now about the rising edge, it should simply be a function of the bandwidth of the generator. If it's properly designed, the best rising edge will be equal to the needed rising edge to generate a sine wave at the rated bandwidth. If it's better or worse than that, it's poorly designed.

[pickle9000]

Comparison and Teardown of Siglent SDG5162 and Rigol DG4162 Arbitrary Waveform Generators

http://thesignalpath.com/blogs/2014/12/08/review-comparison-and-teardown-of-siglent-sdg5162-and-rigol-dg4162-arbitary-waveform-generators/

[LabSpokane]

This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.

On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.

The primer:
http://cp.literature.agilent.com/litweb/pdf/5989-5733EN.pdf

[Pjotr]

What is a good square wave? It's one that fulfils your needs, not a theoretical one drawn with a ruler. On the other side you need a scope with sufficient bandwidth an phase linearity (lack of overshoot) to judge that square wave and the DUT tested with it. And what is affordable then? Depends if your interest is just audio gear or do you plan satellite building or complex high speed data communication stuff?

Here my 2 cts. My  DG4102 hooked to a DS2102, my standard home hobby set-up. It is a 10 MHz square wave of the DG4102. Top trace is with a 50 ohm standard lab cable terminated externally with an external 50 ohm  terminator at the scope. Bottom trace is with a 350 MHz/9 pF HF probe connected to a BNC to probe adapter and terminated with a 50 ohm feed through at the generator side. Not much of a difference to see.

At 10V pp:



At 1V pp:



It fulfils my needs for hobby nicely

[T3sl4co1l]

I'm pretty sure the scope isn't a limiting factor here. We're talking about square waves of 25MHz and below and 3GHz (120 times the frequency of the 1st harmonic) is more than enough bandwidth to capture all relevant frequency components. The scope has also been calibrated pretty recently.

Not the fundamental, but the risetime: scope should be in the 300ps range, so at 8-9ns, it's *definitely* the generator's fault (or... anything inbetween, but..).  Which suggests a bandwidth around 43MHz, which seems consistent with the lumpy "square" at 25MHz.

The cable has been tested a while ago up to 600MHz. I also did a quick comparison with a brand new 1m RG-58 cable and the results are the same (both cables are high quality cables and not some cheap chop suey stuff).

That's actually contradictory: you can't have RG-58 that's not "chop suey".  The original spec for the stuff is terrible.

Cable that's compliant with the RG-58 spec can be pretty crappy, or pretty good.

Most of the good stuff is made in the same dimensions, but with better construction and materials, and given proprietary manufacturers' numbers.  Belden 9223 for instance.

If you tested its attenuation at 600MHz and it considerably exceeds RG-59 (and more to the point: is only a few dB at ~50MHz), then it's more than enough for this waveform.

When I see top and bottom ringing, what are the possible origins of that error?

Difficult to say but I'm sure it's from the AWG. Maybe there's a mis-match with the internal termination (I'll see if I can check with external termination tomorrow).

I also noticed that at higher frequencies the DG1062z shows some slight jitter.

I would guess:
- Risetime limited by antialias filter (blah!)
- Ringing possibly residual from filter or internal circuitry, else possibly Zout or line mismatch
- Slight attenuation of the leading edge of the top, possible line loss, but easily also possible due to generator

Tim

[T3sl4co1l]

Wavetek 193, ~10ns rise, 20MHz range, sine/triangle/square, aux generator, AM/FM/sweep modulation, gating, triggering.

Another vintage: Eico 377



Starts with a sine (Wien bridge RC oscillator) that's clipped to a square.  So the rise/fall time is pretty terrible. 

Tim

[Lukas]

I've done some experiments using an ON Semiconductor NBSG11 and some kind of oscillator: That's what I got (sorry for the crappy image, I've only had my mobile phone with me and this thing only saves to floppy disk...):
Scope is an 20GHz Sampler in some old HP 'Digital Communication Analyzer'.





See this thread: http://www.mikrocontroller.net/topic/295617#3335040 (German) for more infos and pics.

I've done an improved version where I mounted the NBGS11 dead-bug-style and directly connected it to SMA connector, didn't come out much better, but was a royal pain to assemble. I'll have to see were I got pictures of that one...

[ovnr]

Keithley 3390 50MHz ARB @ 25 MHz into a shitty GW Instek GDS-2104 100MHz scope. 50-ohm terminated.

[tautech]

Few variations of that posted before for the record. 
Siglent SDG1010 @ 10 MHz 50 Ohm source & internal DSO termination. RG58C/U.
AS previously posted.


10 MHz same cable, 50 Ohm source, 50 Ohm feed-through TEK termination, 1 M DSO input


10 MHz High Z output, DSO 300 MHz probes,10x 1x, 1 M DSO input

[Alex Eisenhut]

Home made ARB I built for a home project back in the 80s.    It can record and playback.  No DSO at home back then....     6800 based, used some 3055s for the

That's gotta be the best-looking home made anything from the 80s I've ever seen.

[BloodyCactus]

here is a 1, 5, 10, 15mhz square wave from my DG1032Z to a DS2202A

[alex.forencich]

Not exactly a square wave, but here is an eye diagram of 10G Ethernet 64b/66b idle code as received with an Eoptolink DWDM SFP+ module with limiting amp, recorded on an Agilent DSA91304A.  The module is mounted in a Finisar SFP+ dev board with the receive differential output directly connected to channels 1 and 3 on the scope with SMA cables.  The transmitter is another Eoptolink DWDM SFP+ module in a Myricom 10G NIC, with a 90/10 tap to loop the signal back in to the transmitter to keep the link up (sigh...).  An optical attenuator in-line sets the receive power to -8 dBm.  Period is 200 ps, risetime about half of that.  Scope is running at 40 GSa/sec realtime with 13 GHz analog bandwidth. 

[joeqsmith]

Home made ARB I built for a home project back in the 80s.    It can record and playback.  No DSO at home back then....     6800 based, used some 3055s for the

That's gotta be the best-looking home made anything from the 80s I've ever seen.

Thanks!   Back then I had to build a lot of my equipment.   Here are a few pictures of it...

Next to my Hitachi analog scope.   


Some of the main board.


Top of the main controller board.

[pickle9000]

Home made ARB I built for a home project back in the 80s.    It can record and playback.  No DSO at home back then....     6800 based, used some 3055s for the

That's gotta be the best-looking home made anything from the 80s I've ever seen.

Thanks!   Back then I had to build a lot of my equipment.   Here are a few pictures of it...

Next to my Hitachi analog scope.   


Some of the main board.


Top of the main controller board.

Beautiful job.

[Smokey]

You want square waves... I'll give you square waves!!!!


Sorry.  I just wanted to be a part of this killer thread and I don't have any really nice square wave equipment.

Edit to add source:
http://en.wikipedia.org/wiki/Cross_sea
http://en.wikipedia.org/wiki/Cnoidal_wave

[tautech]

You want square waves... I'll give you square waves!!!!


Sorry.  I just wanted to be a part of this killer thread and I don't have any really nice square wave equipment.

Classic. 

[Rupunzell]

The ripples at the top of the step response are likely due to the impedance mis-match between the output of that active device, board to connector launch, non-linear board dielectric effects at these frequencies and more. Improvement means using the required RF_microwave board dielectric, designing a proper board to SMA connector launch with impedance matching network to a normalized 50 ohm load. This is the kind of stuff microwave folks do often. The same rules applies to the picosecond pulse world.

Physically small size alone will not achieve optimum impulse response.


Bernice

I've done some experiments using an ON Semiconductor NBSG11 and some kind of oscillator: That's what I got (sorry for the crappy image, I've only had my mobile phone with me and this thing only saves to floppy disk...):
Scope is an 20GHz Sampler in some old HP 'Digital Communication Analyzer'.





See this thread: http://www.mikrocontroller.net/topic/295617#3335040 (German) for more infos and pics.

I've done an improved version where I mounted the NBGS11 dead-bug-style and directly connected it to SMA connector, didn't come out much better, but was a royal pain to assemble. I'll have to see were I got pictures of that one...

[Rupunzell]

Nice to see a properly instrumented and presented picosecond pulse waveform.
Well and properly done.


Bernice

Tek R7103, S4 with sampling head extender connected straight to Tek 284 pulse generator.

[Rupunzell]

This discussion with images has gone a ways to show how proper instrumentation should be done and all the things that can go so very wrong. A single mis-step in the instrumentation set up and the results will easily mis-lead resulting in a very wrong conclusion of circuit or instrument behavior.

Stuff that can go wrong and it becomes increasingly difficult as the rise times shrink and transmission distances grow.

*Poor coax performance. Common RG58 is pretty poor for any serious RF work. This why semi-rigid coax, Gore, Huber-Suhner and similar coax cables with known specifications should be used for nanosecond-picosecond pulse work. Beyond losses as frequency goes up, coax cables often have dispersion which compounds the problems.

*Impedance match for all component in the system. Deviations cause ripples and reflections in the response.

*Don't trust the scope image alone, know what to expect before setting up the instrumentation and if those results do not appear figure out why.

*No matter how much automation, quality-state of the art instrumentation or what not understand every tiny aspect of the test set up. As frequencies goes up, levels goes down and related are pushed to extremes all it takes is one tiny item wrong and BIG errors happen.

*Keep in mind what one is trying to achieve with the measurement as over kill is not always needed to get the desired result. There is a balance here. One does not need a picosecond pulser with matching instrumentation  to test an audio amplifier.

*Then there are probes.. which are an entire universe of good and bad, some times REALLY BAD.


Bernice
 

This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.

On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.

[DIPLover]

10, 20 and 40MHz square waves from Altera Stratix FPGA Enhanced PLL to Tektronix 2465. CMOS 2.5V IO standard.

The old boat anchor is still beating specs (a little) 30 years after being built (and 10 years after last pro calibration sadly  )

[T3sl4co1l]

Nice to see something old enough to be in KC.   I bet the lamp holder is actual glass.    Any idea on the age?  50s?    I can just see someone driving their high tech relay logic with this back in the day!   

Ahem, I posted a waveform from an Eico 377 earlier..

To be fair, it's probably a kit from the 50s or 60s, but the tech is certainly up there in age.

Tim

[jpb]

Here is an historic one from a Levell TG150D that I've just been given and hope to restore (it is very noisy at present).

The maximum it can do is 2.5V and 160kHz (nominal 150kHz but the dial goes a bit higher).

EDIT:
I realise that I had the attenuated set for 20dB so I've added a shot with it off below.

Nice to see something old enough to be in KC.   I bet the lamp holder is actual glass.    Any idea on the age?  50s?    I can just see someone driving their high tech relay logic with this back in the day!   

This model actually made it into "Journal of Scientific Instruments" page 34 Vol 38 January 1961.
The particular one I got was rescued from a skip when one of the Cambridge University Physics Labs was having a clear out. So it is 60s rather than 50s and has probably been abused by generations of physics students.

EDIT : I attach a photo of the Journal excerpt.

[Wuerstchenhund]

That's actually contradictory: you can't have RG-58 that's not "chop suey".  The original spec for the stuff is terrible.

Indeed, but the cable I have is slighlty better:
http://www.pasternack.com/images/ProductPDF/RG58C-U.pdf

All I wanted to say is that the cable is not one of the the $2 items from ebay.

[Yago]

This discussion with images has gone a ways to show how proper instrumentation should be done and all the things that can go so very wrong. A single mis-step in the instrumentation set up and the results will easily mis-lead resulting in a very wrong conclusion of circuit or instrument behavior.

Stuff that can go wrong and it becomes increasingly difficult as the rise times shrink and transmission distances grow.

*Poor coax performance. Common RG58 is pretty poor for any serious RF work. This why semi-rigid coax, Gore, Huber-Suhner and similar coax cables with known specifications should be used for nanosecond-picosecond pulse work. Beyond losses as frequency goes up, coax cables often have dispersion which compounds the problems.

*Impedance match for all component in the system. Deviations cause ripples and reflections in the response.

*Don't trust the scope image alone, know what to expect before setting up the instrumentation and if those results do not appear figure out why.

*No matter how much automation, quality-state of the art instrumentation or what not understand every tiny aspect of the test set up. As frequencies goes up, levels goes down and related are pushed to extremes all it takes is one tiny item wrong and BIG errors happen.

*Keep in mind what one is trying to achieve with the measurement as over kill is not always needed to get the desired result. There is a balance here. One does not need a picosecond pulser with matching instrumentation  to test an audio amplifier.

*Then there are probes.. which are an entire universe of good and bad, some times REALLY BAD.


Bernice
 

Good post, thanks.
To see great square waves is one thing, explanations like yours fill in the whole picture.
Without that, all that is learned is "so and so, has the best square wave, and kit".
Well from my meagre perspective that is!

Oh and welcome to EEVBlog

My rise time is going to be about 6 weeks until I get delivery of 1054z!

[Electro Fan]

10, 20 and 40MHz square waves from Altera Stratix FPGA Enhanced PLL to Tektronix 2465. CMOS 2.5V IO standard.

The old boat anchor is still beating specs (a little) 30 years after being built (and 10 years after last pro calibration sadly  )

Nice scope indeed and your DUT produces some very good looking square waves.

Is this what you were testing?

http://www.altera.com/devices/fpga/stratix-fpgas/stratix/stratix/features/stx-pll.html

[Rupunzell]

Sounds like an "solid state" version of the Bill Hewlett's audio oscillator with a square wave output made in the UK.

Does design this use a light bulb as a non-linear resistor to regulate feed back in the same way as Bill Hewlett's design and masters thesis at Stanford U.


Bernice

Here is an historic one from a Levell TG150D that I've just been given and hope to restore (it is very noisy at present).

The maximum it can do is 2.5V and 160kHz (nominal 150kHz but the dial goes a bit higher).

EDIT:
I realise that I had the attenuated set for 20dB so I've added a shot with it off below.

Nice to see something old enough to be in KC.   I bet the lamp holder is actual glass.    Any idea on the age?  50s?    I can just see someone driving their high tech relay logic with this back in the day!   

This model actually made it into "Journal of Scientific Instruments" page 34 Vol 38 January 1961.
The particular one I got was rescued from a skip when one of the Cambridge University Physics Labs was having a clear out. So it is 60s rather than 50s and has probably been abused by generations of physics students.

EDIT : I attach a photo of the Journal excerpt.

[EV]

Rigol DS2202, DG4000:

[Rupunzell]

Compare that RG-58 stuff with Gore instrumentation coax.
http://www.gore.com/en_xx/products/cables/coaxialmicrowave/test/gore_phaseflex_microwave_test_assemblies.html


How good does it need to be is the real question. In most cases, RG-58 is OK to use for lower frequency work. Cables are also microphonic which can be serious if small signal are involved.

Using the wrong cable-interconnect often ends in big fat tears and much frustration for trying to figure out why are the signals so very wrong.


Bernice

That's actually contradictory: you can't have RG-58 that's not "chop suey".  The original spec for the stuff is terrible.

Indeed, but the cable I have is slighlty better:
http://www.pasternack.com/images/ProductPDF/RG58C-U.pdf

All I wanted to say is that the cable is not one of the the $2 items from ebay.

[LukeW]

Not mine, but if you want a fast scope, there is some history, teardown pics and discussion of the beautiful Tek 519 here: http://www.timkoeth.com/?p=108

[tautech]

That's actually contradictory: you can't have RG-58 that's not "chop suey".  The original spec for the stuff is terrible.

Indeed, but the cable I have is slighlty better:
http://www.pasternack.com/images/ProductPDF/RG58C-U.pdf

All I wanted to say is that the cable is not one of the the $2 items from ebay.

Compare that RG-58 stuff with Gore instrumentation coax.
http://www.gore.com/en_xx/products/cables/coaxialmicrowave/test/gore_phaseflex_microwave_test_assemblies.html


How good does it need to be is the real question. In most cases, RG-58 is OK to use for lower frequency work. Cables are also microphonic which can be serious if small signal are involved.

Using the wrong cable-interconnect often ends in big fat tears and much frustration for trying to figure out why are the signals so very wrong.


Bernice

Many don't require cable connection for more than a few tens of MHz and as you say RG58 is fine and cheap enough for ppl to use.
More than 100 MHz and signal components with fast risetimes is a different story and quality cables should be sought.

Bernice thank you for your fresh input, no doubt you have more to offer. 
Can I make the suggestion that you quote before your reply as it makes the post easier to read.
Sort of like how I've amended your last post. 

[jpb]

Sounds like an "solid state" version of the Bill Hewlett's audio oscillator with a square wave output made in the UK.

Does design this use a light bulb as a non-linear resistor to regulate feed back in the same way as Bill Hewlett's design and masters thesis at Stanford U.


Bernice

In the circuit diagram the light bulb is only used as a battery check and there is a thermistor for temperature feedback.  Of course the thermistor might actually be another light bulb -  I've not taken it apart to have a look yet.

[jancumps]

Metex MS-9150 2 MHz

Square wave output loaded with 50 Ohm:


TTL output:

[MartyD]

A few screenshots from my Siglent SDG1025, taken with the SDS1102CML, 1m Coax, 50Ohm terminator:

[Wuerstchenhund]

Many don't require cable connection for more than a few tens of MHz and as you say RG58 is fine and cheap enough for ppl to use.
More than 100 MHz and signal components with fast risetimes is a different story and quality cables should be sought.

The problem with RG-58 is that the original spec was very poor. Many modern variants are much better but the variation between RG-58 cables can be huge. I'd always use a good quality cable (Gore is fine, although I prefer Huber & Suhner and Pasternack).

Bernice thank you for your fresh input, no doubt you have more to offer. 
Can I make the suggestion that you quote before your reply as it makes the post easier to read.
Sort of like how I've amended your last post. 

Save your breath. He's pretty deaf on that ear 

[Electro Fan]

Hi, Thanks to all the posters for the good examples and info.  There are lots of questions that could be asked about what constitutes a "strong" square wave (I think "strong" is probably NOT an official technical term  ).  (And certainly, one set of questions revolves around the ability to generate and render excellent rise times but I'll leave that for another post.)

I realize that there are many setup variables that can contribute to how waveforms render (generator equipment, cabling, termination impedance, scope capabilities, etc, etc.).  My questions here are somewhat less about the equipment and setup - and more about how to read/interpret what is displayed.

Below are two examples:  one from a Rigol DG1032Z and one from a Rigol DG1062Z - presumably similar other than bandwidth.  Admittedly, they are each hooked to different scopes (the 1032 to a Rigol DS2022A and the 1062 to a LeCroy 7300A) and likely with different cables.  Additionally, I could be wrong but I think the  1032 was probably terminated into 1 Mohm on the Rigol vs. 50 ohms on the LeCroy.  (The bandwidth on a Rigol 2202 is typically 200MHz and I think it's 3GHz (with 20GSa/s!) on the LeCroy 7300 - big difference and probably there is a healthy difference in price too.)

Given all that my questions are about the level of detail seen on the two images.  In particular, the images from the 1032 on the 2202 are pretty distinct (sharply detailed?).  They show a pretty defined ringing at the tops and bottoms.  The images from the 1062 on the 7300 don't seem to convey the ringing as distinctly.  Perhaps there is less ringing shown on the 1062/7300 because of 1) the 50 ohm termination? (doubtful but maybe?), 2) the extra bandwidth of the 1062 vs. the 1032? (doubtful but maybe?), 3) better cabling?, or 4) the extra bandwidth and sampling of the 7300? (I don't know the specs on the display resolution - maybe that's better too on the 7300 but I'm betting it's the outstanding bandwidth and sampling of the 7300 that we are seeing), or 5) maybe it's something else?  On a related observation, the tops and bottoms of the 1062/7300 combination appear much thicker than the tops and bottoms of the 1032/2202.   Perhaps this is due to the ability of the 7300 to process and resolve (and ultimately display) noise more accurately beyond what the 2202 can resolve and display.  Interestingly, the thicker tops and bottoms on the 7300 seem to be of an amplitude roughly similar to the ringing that is seen on the 2202.  Perhaps that is why the ringing is not so evident on the 7300 (ie, the ringing is hidden in the noise)? 

Net, net:  which setup (the 1032/2022 or the 1062/7300) most accurately represents the phenomenon occurring?  Is the waveform on 1032/2022 setup cleaner/more defined/more accurate or is it missing information that is being revealed by the 1062/7300 setup?  I'm betting the difference is that the 2022 simply can't render the information as accurately as the 7300 but I'm curious to know...

Thanks, EF

PS, one other observation:  the Rigol seems to use square divisions and the LeCroy uses rectangular divisions - a bit off topic but an observation...

[Pjotr]

Don't see much different about the ringing. With the LeCroy it's more buried in the noise of the scope.

[G0HZU]

Jeez... Some of the low frequency squarewave plots from the modern stuff from Rigol and Siglent are less than impressive.

I'm not really into pulse risetime races but I do have some ancient and low spec pulse generators from the 1970s here. eg the bargain basement 10MHz models from HP or Datapulse and they produce nicer square waves at 1MHz and 5MHz. (HP8002A and Datapulse 101) The Datapulse claims a risetime of 5ns and the HP is about 10ns. I paid £5 for each of them about 20yrs ago at a ham surplus sale.

Do people really accept that level of performance from Rigol? Looks woeful compared to basic old school stuff that was designed and built about 40 years ago.

Note: I just noticed that the later plots from the Siglent gear look to be better. So maybe the first plot was poorly set up?

[Yago]

With all the talk of cable and connector quality, what (and where from in UK) would qualify as reasonable up to say 150Mhz, for a BNC to BNC patch?
 
Cheers

[jancumps]

Jeez... Some of the low frequency squarewave plots from the modern stuff from Rigol and Siglent are less than impressive.

I'm not really into pulse risetime races but I do have some ancient and low spec pulse generators from the 1970s here. eg the bargain basement 10MHz models from HP or Datapulse and they produce nicer square waves at 1MHz and 5MHz. (HP8002A and Datapulse 101) The Datapulse claims a risetime of 5ns and the HP is about 10ns. I paid £5 for each of them about 20yrs ago at a ham surplus sale.

Do people really accept that level of performance from Rigol? Looks woeful compared to basic old school stuff that was designed and built about 40 years ago.

Note: I just noticed that the later 5MHz plots from the Siglent gear look to be better  so maybe the first plots were poorly set up?

I'd be careful to draw too much conclusions out of this thread.  We're all having good fun - but not all of us may have used state-of-the-art measuring methods.
Mainly looking at myself here

[BloodyCactus]

well, the 1032 screen shot is mine, I used the cable that came supplied with the unit (1032Z), and it was into the rigol at 1Mo, the square wave was 5vpp, 50% duty cycle. rigol dont give specs on the provided cable.

note, if I use the 300mhz option the ringing is much worse.

here is the 50mohm of 1mhz.

[G0HZU]

I took a quick image of the HP8002A generator response on my Tek 465 when the HP8002A is giving a 10MHz squarewave. This is on (50ns/div x10) so it is 5ns/div.

It doesn't look bad for a basic 10MHz pulse gen that was made about 40 years ago. I expected the modern gear to be far better than this?

[N2IXK]

Hewlett Packard 3312A function generator @ ~7.5 MHz, displayed on Tektronix 7904 w/7A26 amplifier. Connected directly to scope input via 3' of RG-58, terminated w/50 ohms via T connector at scope input.

[miguelvp]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

[G0HZU]

Here's the old Datapulse 101 (1970s vintage?) at 10MHz on 5ns/div and you can see it just meets its published spec for 5ns risetime. However, the Tek 465 risetime will be starting to limit the performance here.

However, the quality of the squarewave isn't as nice as the HP8002A as it looks quite lumpy.

[pedroteck]

70s hung chang 5502 20 MHz cro .

[Yago]

What frequency signal Pedro ?

[tautech]

EF
That both DSO's display the ringing artifacts of the waveform is the inportant thing, even though they are from 2 FG's.
This ringing implies a cable or termination problem.
Have you set the FG output for 50 Ohms or Hi Z as required by the termination available?

Yes the LeCroy will resolve and display more info as a result of its much higher sampling rate.

Your LeCroy has 10 horizontal divisions as was the norm until recently whereas the Rigol has 12.
MartyD's Siglent SDS1000 series shows 15 with the Menu out, 18 with the menu hidden.
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg588973/#msg588973

Accuracy.
Set your AWG to a P-P level and read the resultant P-P level on the scope.
Termination method WILL influence result.
Carefull study af preceeding posts will display these errors as a result of sub-optimal connections.

[Electro Fan]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

[AlfBaz]

Here's a shot of a Wavetek 395 at 20Mhz into 50ohm. It can go up to 50Mhz but it's pretty much sine looking beyond 25Mhz

[Wuerstchenhund]

With all the talk of cable and connector quality, what (and where from in UK) would qualify as reasonable up to say 150Mhz, for a BNC to BNC patch?

http://uk.pasternack.com/
http://www.hubersuhner.com/en-gb/

I buy my BNC RG-58 and other RF cables from them.

[tautech]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

If it's other than 50% duty it's a PULSE and EF asked for squarewaves.

Most AWG's have a different spec for pulse as opposed to square wave and to post them is confusing fair comparison.

[Electro Fan]

Anyone have a Tektronix AFG 3000 to show off at 10, 20, or 30 MHz?

[Electro Fan]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

If it's other than 50% duty it's a PULSE and EF asked for squarewaves.

Which is more challenging to produce? A pulse?

[tautech]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

If it's other than 50% duty it's a PULSE and EF asked for squarewaves.

Which is more challenging to produce? A pulse?

IME a clean square wave with a fast risetime

[Yago]

With all the talk of cable and connector quality, what (and where from in UK) would qualify as reasonable up to say 150Mhz, for a BNC to BNC patch?

http://uk.pasternack.com/
http://www.hubersuhner.com/en-gb/

I buy my BNC RG-58 and other RF cables from them.

Thanks Mr hound, may the Walls be with you

[Electro Fan]

As long as we are wandering around the topic a bit, and not to state the obvious, but in case it helps anyone, if you want to compare the effect of cables (different materials, lengths, etc.) an easy way to do it is to attach two alternative cables to a two channel generator and set the channels for tracking - then change frequencies, amplitude, etc. and watch rise times and fall times, etc. on your scope. 

[miguelvp]

DE0-Nano driving an ADV7125 3 channel video DAC capable of 330MHz (8 bits per color)

Not a perfect 50% duty because I was just playing around trying to push it. Not a very clean solution as you can see.

75 Ohm terminated as I recall because it's hooked to a VGA output, and I have a VGA to BNC cable.

12.50MHz (DAC running at 50MHz but needs 4 points for a square wave)


82.51MHz (4 points, low,low,high,high at 330.04 MHz max of what that DAC can do)


The limitation is most likely the FPGA PLL and my coding, the driving clock I believe is derived from the on board 50MHz or it could be 25MHz crystal.

[K6EEP]

OMG I just hooked up my Wun Hung Lo factory signal generator to my Tektronics TDS 2014B 100Mhz scope.  A 1Mhz square wave looked so bad it won't sync to it. The edges have so much ringing on them that it's impossible to see a flat spot.  It just looks like hair in a mullet pattern. I even tried different cables and lower frequencies. No better.
There is a small section on the top of the waveform where a flat spot can be seen.  So that leads me to believe it is in fact a square wave.
Looks like I am going to save up for a new signal generator next. 
I appreciate this thread.  It got me off my bum and made me look. 
Thanks!

[miguelvp]

Like the video DAC.    Show some pictures of the board!

Here you go, board is on the right attached to the inclined FPGA DE0-Nano:



The input clock feeding the PLL is 50MHz, this is from a video converter project that it is dormant at the moment:


Here is a picture of the board from where I bought it, the connector is compatible with the Altera GPIO 40 pin connector:



Not all of the pins from the connector are wired to the top connector btw, which is very strange they didn't do that. I would have loved they did so I could use the unused pins for other things.



Here is where I got it from:
http://www.wayengineer.com/digiasic-fpga-adv7125adv7123-vga-board-p-160.html

[tautech]

OMG I just hooked up my Wun Hung Lo factory signal generator to my Tektronics TDS 2014B 100Mhz scope.  A 1Mhz square wave looked so bad it won't sync to it. The edges have so much ringing on them that it's impossible to see a flat spot.  It just looks like hair in a mullet pattern. I even tried different cables and lower frequencies. No better.
There is a small section on the top of the waveform where a flat spot can be seen.  So that leads me to believe it is in fact a square wave.
Looks like I am going to save up for a new signal generator next. 
I appreciate this thread.  It got me off my bum and made me look. 
Thanks!

Welcome to the forum.
Before you do have you read all of this thread?
Termination is very important to inhibit ringing.
Look at miguelvp's setup and see the Tee BNC's terminated with 50 Ohms on his scope inputs.

First try a similar setup before you spend up.

[miguelvp]

Just to point out, that the purple terminators are 75 Ohms (VGA is terminated that way) the green one is 50 Ohms that I connected to the  vertical sync (just because I didn't have more 75 Ohms terminators).

[tautech]

As long as we are wandering around the topic a bit, and not to state the obvious, but in case it helps anyone, if you want to compare the effect of cables (different materials, lengths, etc.) an easy way to do it is to attach two alternative cables to a two channel generator and set the channels for tracking - then change frequencies, amplitude, etc. and watch rise times and fall times, etc. on your scope.

Here's one I set running a for while after Self Cal of both Siglent SDS2304 & SDG1010.
Both AWG channels checked for SAME settings ie.
10 MHz square wave, 3 V p-p, 50 Ohm source

DSO
50 Ohm internal termination
Statistics ON for ~20,000 counts then image saved.
Delay 5ns for ease of reading stats. 

Cables
AWG Ch 1: 1M RG-58C/U as used previously to DSO Ch 1
AWG Ch 2: 500 mm unknown brand/spec/type to DSO Ch2

Seen are some interesting variations in the Mean values recorded.
Risetime in particular between the 2 AWG channels with 0.6ns variation, Channel 2 the slower.
But to be fair Ch 2 is operating at its max 3 V P-P output into 50 Ohms.
Both channels have risetimes nearly twice as fast as the spec'ed 12 ns and as good as the published 7ns Pulse specs.



But what about the unknown spec cable?
Now we have the unknown cable from AWG Ch1 to DSO Ch2.(cables swapped at AWG)
You can see in the stats how the unknown cable risetime is now faster as a result of the greater drive capability of Ch1 of the AWG.



So lets reduce the P-P voltage to a lower level that AWG Ch2 is more capable of driving. (not max'ed out)
The Risetime, V p-p and Std Dev values are now MUCH closer between channels.
AND it seems at 10 MHz this unknown cable has little affect on results. 

[EV]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

Yes it is DG4162 and output is set to 160 sine wave. The scope is connected to sync out connector which gives 40 MHz square wave pulse when output is at 160 MHz sine wave. Rise time is about 1.5 ns measered with DS2202 (BW set to 300 MHz option).

[TMM]

Hah, I was wondering how you managed to get such a nice square wave out of a DG4000.

Here is a DG4062 (mod -> 'DG4202') and DS1054Z (mod -> DS1104Z) using the sync output:


And not cheating (using DAC output):

[Coliban]

Siglent SDG5082 to Siglent1102CML

I soldered 50 Ohm Resistors to the connectors, then it looked better.

[EV]

Hah, I was wondering how you managed to get such a nice square wave out of a DG4000.

Here is a DG4062 (mod -> 'DG4202') and DS1054Z (mod -> DS1104Z) using the sync output:

You have mod DG202. What is the frequency of sync output if you set output to 200 MHz sine? Is it 50 MHz square wave pulse or is it still 40 MHz?

[Rupunzell]

There are a great number of variables at work here. Everything from cables, connectors, overall set-up, instrumentation and more affect the visual results.

If one were to dig into vintage pulse/square wave generators there are often a number of adjustment to get optimized pulse response at the output. Notables would be EH-Research, Datapulse, Hewlett-Packart, Tektronix and others.

There was a time when folks who worked with this stuff really cared about pulse quality to where it was an engineering speciality (aka pulse engineer). This work was part of early digital where the industry was trying to figure what was do-able, what was not and how good pulses had to be to transmit data with reliability and be robust in a system.

This was the age of tunnel diode, snap diode, hot carrier diode clamped and similar devices were used in pulse / step wave form generation. The picosecond race was on.

In time, high speed logic evolved as the industry gained a much better understanding of how to make pulses go fast, be reliable and more. ECL is a good example of fast logic that can offer low noise if implemented properly. The Hewlett Packard 8640 RF signal generator uses a cavity oscillator with a group of ECL dividers and filters to produce a highly stable and low distortion RF sine wave.

Bottom line, newer is not always better. Often times vintage test gear is looked down upon as old. obsolete and in-the-way-boat anchor. When on balance it really depends on what the measurement needs are as the latest and greatest is not always the ideal solution to any given problem. The ideology of smaller is always better should not be the single parameter of desirability.
 

Bernice

Jeez... Some of the low frequency squarewave plots from the modern stuff from Rigol and Siglent are less than impressive.

I'm not really into pulse risetime races but I do have some ancient and low spec pulse generators from the 1970s here. eg the bargain basement 10MHz models from HP or Datapulse and they produce nicer square waves at 1MHz and 5MHz. (HP8002A and Datapulse 101) The Datapulse claims a risetime of 5ns and the HP is about 10ns. I paid £5 for each of them about 20yrs ago at a ham surplus sale.

Do people really accept that level of performance from Rigol? Looks woeful compared to basic old school stuff that was designed and built about 40 years ago.

Note: I just noticed that the later plots from the Siglent gear look to be better. So maybe the first plot was poorly set up?

[Rupunzell]

How do you know for fact Bernice is a "he"?
It seems every web forum has their wanna be top dog-know it all types.

Bernice

Bernice thank you for your fresh input, no doubt you have more to offer. 
Can I make the suggestion that you quote before your reply as it makes the post easier to read.
Sort of like how I've amended your last post. 

Save your breath. He's pretty deaf on that ear 

[TMM]

Hah, I was wondering how you managed to get such a nice square wave out of a DG4000.

Here is a DG4062 (mod -> 'DG4202') and DS1054Z (mod -> DS1104Z) using the sync output:

You have mod DG202. What is the frequency of sync output if you set output to 200 MHz sine? Is it 50 MHz square wave pulse or is it still 40 MHz?

Just tried it - 50MHz.

[Rupunzell]

Thermistors don't work that well as the FB stabilizing element. The time constant due it physical size and environmental effects makes a thermistor less than ideal choice.

Photo-resistor coupled with a light bulb or similar was commonly used as a control element in stuff like this from that era. Photo-FETs  devices were also made and used during that time. Other ways would have been to use a FET's channel resistance as the FB control element and control circuit.

What is remarkable, the light bulb works amazingly well and is simple.


Bernice

In the circuit diagram the light bulb is only used as a battery check and there is a thermistor for temperature feedback.  Of course the thermistor might actually be another light bulb -  I've not taken it apart to have a look yet.

[Wuerstchenhund]

The following screenshots show again a 1MHz and a 20MHz square wave from a Rigol DG1062z, but this time the scope (LeCroy WavePro 7300A) was running in 11bit ERES mode which limits the bandwidth to 160MHz (which eliminates some of the noise).

[Electro Fan]

There are a great number of variables at work here. Everything from cables, connectors, overall set-up, instrumentation and more affect the visual results.

If one were to dig into vintage pulse/square wave generators there are often a number of adjustment to get optimized pulse response at the output. Notables would be EH-Research, Datapulse, Hewlett-Packart, Tektronix and others.

There was a time when folks who worked with this stuff really cared about pulse quality to where it was an engineering speciality (aka pulse engineer). This work was part of early digital where the industry was trying to figure what was do-able, what was not and how good pulses had to be to transmit data with reliability and be robust in a system.

This was the age of tunnel diode, snap diode, hot carrier diode clamped and similar devices were used in pulse / step wave form generation. The picosecond race was on.

In time, high speed logic evolved as the industry gained a much better understanding of how to make pulses go fast, be reliable and more. ECL is a good example of fast logic that can offer low noise if implemented properly. The Hewlett Packard 8640 RF signal generator uses a cavity oscillator with a group of ECL dividers and filters to produce a highly stable and low distortion RF sine wave.

Bottom line, newer is not always better. Often times vintage test gear is looked down upon as old. obsolete and in-the-way-boat anchor. When on balance it really depends on what the measurement needs are as the latest and greatest is not always the ideal solution to any given problem. The ideology of smaller is always better should not be the single parameter of desirability.
 

Good post and Good history and Amen  to all that!

There was a time when large companies (providers and/or user organizations) would get together to talk about how to make their private networks talk to one another.  This was when 56kbps and 1.5Mbps were as fast as most data traveled.  The first half of almost every first project meeting was the same thing:  "Are you going to give clock or are we going to give clock?  Who is going to give clock?"  I think if I had to do my career over and could pick something to be really good at in a time when it was definitely needed and valuable I'd like to be one of those specialized "Pulse Engineers", and then if I could move up the chain and broaden out I'd go for "Senior Waveform Engineer"    In an ideal lab you could have some of the best vintage gear (when it's still working) and the best of the new gear. 

[Electro Fan]

The following screenshots show again a 1MHz and a 20MHz square wave from a Rigol DG1062z, but this time the scope (LeCroy WavePro 7300A) was running in 11bit ERES mode which limits the bandwidth to 160MHz (which eliminates some of the noise).

That's pretty cool - kind of like being able to dial-in the signal to noise ratio or the Eb/No

[Rupunzell]

Early on in this discussion mention was made of the Hypress PSP-1000 and PSP-750.

The intent of that note was to see of anyone here had a Hypress PSP-1000 or PSP-750. These are 70 Ghz sampling systems that use super-conducting Josephson junction device based time domain instrumentation, circa late 1980's.

These are the same folks who make really fast digital stuff.
http://www.hypres.com/products/


Bernice

[Martin.M]

Oldies @work

Mini-Tek Type221, reading from a EMG Pulse Generator



1967 Mini-Tek Type323, reading from a EMG Pulse Generator


cccp: C1-73 the 323 clone


greetings
Martin

[miguelvp]

Hah, I was wondering how you managed to get such a nice square wave out of a DG4000.

Here is a DG4062 (mod -> 'DG4202') and DS1054Z (mod -> DS1104Z) using the sync output:


And not cheating (using DAC output):

That explains why it wasn't 50% duty cycle

I think I'm going to hookup my video DAC to the FPGA and try 75MHz with the DAC running at 300 MHz since I need 4 points per cycle.
and I will also try to create both a 50 MHz and 40 MHz with the DAC running at 4 times the desired wave since I need two lows and two highs per cycle.

Also running the output to 5V is too much of a swing, since I can adjust the output by 0.01953125V increments I'm going to switch from 0 to 169 decimal (3.30078125 Vpp) that should give me a cleaner wave.

Here is doing a ramp:

[Yago]

Oldies @work

Mini-Tek Type221, reading from a EMG Pulse Generator



1967 Mini-Tek Type323, reading from a EMG Pulse Generator


cccp: C1-73 the 323 clone


greetings
Martin

Wow, three gems there Martin!

[Electro Fan]

A little bit off topic (so what's new?  )



- it's mostly a tutorial on times 10 probe compensation but toward the end (about 3:20) the presenter makes the point that probe compensation is done on square waves because we know what a good sharp edged (or in my words "strong") square wave is supposed to look like (which is often not the case with other waveforms) - and if we don't get a proper square wave we probably don't get any other waveforms properly displayed.  Just re-enforcing one of the reasons I think there is a fair amount of interest in this topic.

[Yago]

How do you know for fact Bernice is a "he"?
It seems every web forum has their wanna be top dog-know it all types.

Bernice

Bernice thank you for your fresh input, no doubt you have more to offer. 
Can I make the suggestion that you quote before your reply as it makes the post easier to read.
Sort of like how I've amended your last post. 

Save your breath. He's pretty deaf on that ear 

Read back through the thread a little and the joke will make sense.

[miguelvp]

A little bit off topic (so what's new?  )



- it's mostly a tutorial on times 10 probe compensation but toward the end (about 3:20) the presenter makes the point that probe compensation is done on square waves because we know what a good sharp edged (or in my words "strong") square wave is supposed to look like (which is often not the case with other waveforms) - and if we don't get a proper square wave we probably don't get any other waveforms properly displayed.  Just re-enforcing one of the reasons I think there is a fair amount of interest in this topic.

If you notice he has to revisit the compensation several times because he is using a metallic screwdriver and he is touching the screwdriver with his other hand. So use a plastic one that probably came with your probes.

[Martin.M]

gems means germaniums?

the 221 is from the 70`s, also the russian. Both use Fet and silizium parts also.
Some Mini-Tek of the 200 series have IC.
The oldest is this 323, made in the time of the glowing era. (for the money of a car)

And here re more then 3 scopes, but I dont want to flood the forum with Oldies.

greetings
Martin

Tek, 551 


and a 7k

[Yago]

Gems, diamonds.beautiful scopes.

Post the pics in their own thread, I would love to see more of them, sure others would too.
I'd wager there's some great info you have from restoration work you have done (guessing from the great condition they are in).

[joeqsmith]

- it's mostly a tutorial on times 10 probe compensation but toward the end (about 3:20) the presenter makes the point that probe compensation is done on square waves because we know what a good sharp edged (or in my words "strong") square wave is supposed to look like

- kind of curious to see what is the lowest price device is that can produce a really good looking square wave at 1, 5, 10, 20, and 30 MHz? 

If I understand correctly and we agree that the edge rates, settling times, noise .....  are important for a strong looking square wave, if a generator can meet your requirements at the highest frequency, I am curious why you feel it would not meet them at lower frequencies?   

Are there function generators out there that actually fall apart at low frequencies?   AC coupled or something?   Guessing that iPOD and application would not fair well at DC.    I can believe an ultra fast edge rate TDR may not meet your day to day needs but you were clear that you wanted a square, not a pulse.     What other requirements do you have?

Besides using an actual function generator with a square wave feature, we presented using digital buffers to get a square waves.   No one called me out for my free energy square wave, but the point to this was I show using a couple of diodes to clamp a sine to get the square.    Maybe you can use what you have available to get the job done.   

It's rare I have a need for a square wave that comes out of OTS function generator.   Normally I have to put some sort of drive on it anyway to get what I need.


Like the tiny scopes. 

That's a nice little setup with the FPGA and video DAC.   You could make a real nice ARB with that.  This video shows one I made that puts out the signals to an fuel injection system so it thinks it's on a motor.   


The sound (crappy) is even digital.  The only thing analog is the power supply and drivers.  Pretty much DC compared to what you have.




 
 

[Pjotr]

Brings up the question: "What is the use of a strong looking square wave" 

[miguelvp]

That's a nice little setup with the FPGA and video DAC.   You could make a real nice ARB with that.  This video shows one I made that puts out the signals to an fuel injection system so it thinks it's on a motor.   


The sound (crappy) is even digital.  The only thing analog is the power supply and drivers.  Pretty much DC compared to what you have.

Neat, I was the lead programmer for NHRA Drag Racing games, we did have a deal with RacePak and we integrated the game simulated telemetry into the full RacePak acquisition software (included with the game but with a license that would only work with the PC sim).

We did simulate everything and it was cool to actually use the same data acquisition software that the teams used.

I'm amazed the game still sells for quite a bit of cash since it's a 10 year old game
http://www.amazon.com/NHRA-Drag-Racing-Top-Fuel-Thunder/dp/B0002EA5Z4
And the previous version still holding on price as well and that's 14 years old
http://www.amazon.com/NHRA-Drag-Racing-Main-Event-PC/dp/B00005Y3YX

Edit: as I recall I think the launch MSRP was only $20, I guess they are hard to find

Sorry no motorcycle drag racing. And I don't see a penny of those sales since Moto1 is long gone, so it all goes to Valuesoft I would think. Of course the online servers are long gone.

Back on topic, I did misplace the DAC but just found it, so I'm going to do some tests.

[pedroteck]

What frequency signal Pedro ?

Don't really remember the settings but its about 1.5 Khz 1 vpp from the internal oscillator .

[Yago]

What frequency signal Pedro ?

Don't really remember the settings but its about 1.5 Khz 1 vpp from the internal oscillator .

Thanks Pedro, and welcome to EEV too

[Electro Fan]

- it's mostly a tutorial on times 10 probe compensation but toward the end (about 3:20) the presenter makes the point that probe compensation is done on square waves because we know what a good sharp edged (or in my words "strong") square wave is supposed to look like

- kind of curious to see what is the lowest price device is that can produce a really good looking square wave at 1, 5, 10, 20, and 30 MHz? 

If I understand correctly and we agree that the edge rates, settling times, noise .....  are important for a strong looking square wave, if a generator can meet your requirements at the highest frequency, I am curious why you feel it would not meet them at lower frequencies?

I didn't mean to imply that if a generator can produce a good looking sine wave at one frequency that it would not be able to produce a good looking sine wave at a lower frequency.

I'm pretty confident that if a generator can produce a good looking sine wave at any frequency that it will do as well or better lower frequencies.

The question was just aimed at trying to determine the lowest price point a generator could produce a good looking sine wave at the various frequencies I mentioned.

[Electro Fan]

Brings up the question: "What is the use of a strong looking square wave" 

Well, uh, keeping track of bits when doing computing and networking....

[TMM]

Here is a DG4062 (mod -> 'DG4202') and DS1054Z (mod -> DS1104Z) using the sync output:

Hello TMM,

my signal looks different with the DS1104Z.
The same signal in the second image is of a MSO2302A (org. MSO2072A).

Peter

Interesting. It could be that my 50ohm termination isn't the best and is ringing a bit - i've got a BNC tee on the scope input with an ebay spec terminator on one side and 1m of RG58 going to the function gen on the other.

[Electro Fan]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

Yes it is DG4162 and output is set to 160 sine wave. The scope is connected to sync out connector which gives 40 MHz square wave pulse when output is at 160 MHz sine wave. Rise time is about 1.5 ns measered with DS2202 (BW set to 300 MHz option).

What does a square wave look like at 40MHz when it is connected to Channel 1 rather than Sync Out?  Thx

[TMM]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/?action=dlattach;attach=130307;image

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

Yes it is DG4162 and output is set to 160 sine wave. The scope is connected to sync out connector which gives 40 MHz square wave pulse when output is at 160 MHz sine wave. Rise time is about 1.5 ns measered with DS2202 (BW set to 300 MHz option).

What does a square wave look like at 40MHz when it is connected to Channel 1 rather than Sync Out?  Thx

See reply #120 

[EV]

What does a square wave look like at 40MHz when it is connected to Channel 1 rather than Sync Out?  Thx

See reply #120 

Here are square waves from sync out and output with my DS2202 and DG4162.

[Electro Fan]

The 4162 is pretty respectable - congrats and enjoy!

[Jay_Diddy_B]

Hi group,

Here are some measurements from some classic HP generators. All the measurements are 10 MHz, 4V p-p into 50 Ohms.
All measurements made with a Tektronix TDS744A that was hacked and calibrated to the 1GHz TDS784A.

HP 8116A function generator




HP 8112A pulse generator



HP 3325B function generator




These are all analog based units, no DDS.

Regards,

Jay_Diddy_B

[alterbaron]

Siglent SDG1025 measured using Siglent SDS 1072CML 70Mhz oscilloscope.

The generator was configured to output a 1Vpp signal into a 50 ohm load. The scope doesn't have a 50 ohm mode built-in, so I hooked up a BNC triple jack with a 50 ohm terminator at the scope input. Infinite persistence is turned on for every image. The scope was left to settle for about 30s before capturing each image.

Rise time is measured at just over 5ns, which is pretty good. (Bandwidth can be approximated as 0.35 / (rise time), so we can't expect any faster than a 5ns rise on a 70MHz scope.)
Actual rise time should be <5ns.

If I crank the output up to 5Vpp (max output voltage into 50 ohms at 25MHz), the rise time is measured as 6.8ns.

The last couple of pictures show the waveform generated when configured for 1MHz 1Vpp output. Rise time is pretty much the same.

[Wuerstchenhund]

Siglent SDG1025 measured using Siglent SDS 1072CML 70Mhz oscilloscope.

[...]

If I crank the output up to 5Vpp (max output voltage into 50 ohms at 25MHz), the rise time is measured as 6.8ns.

Forget the 25MHz screenshots, they show garbage if your scope only has 70MHz bandwidth (which isn't enough for a 25MHz square wave).

[alterbaron]

Forget the 25MHz screenshots, they show garbage if your scope only has 70MHz bandwidth (which isn't enough for a 25MHz square wave).

Good point, thanks.

[rf-loop]

Forget the 25MHz screenshots, they show garbage if your scope only has 70MHz bandwidth (which isn't enough for a 25MHz square wave).

Good point, thanks.

Here is SDS1072CML frequency response.


Here is your SDG1025 square


Square wave is series of sinewaves 1. in this example 25MHz fundamental freq. Then harmonics, 3,5,7,9,11,13...etc (levels depending risetime (and other things in real signal shape))
Look freq response even 5th is attenuated over 3dB and 7th attenuated over 6dB

It explain well your square wave images including also my knowledge about SDG1025.

25MHz square fundamental f is 25MHz, then next harmonic is 75MHz, then next 125MHz and next 175MHz and next 225.   (if we have enough fast risetime it continue lot of more.)

With SDG1025 risetime SDS1072CML is just barely enough for this SDG square but it do not show SDG square shape exactly (it can see just there in top after rising endge an bottom after dalling edge. Now here come also SDG1025 risetime to limiting factor... so we do not need very wide BW oscilloscope. (also SDG1025 own filters... there is same rules about produced signal harmonics levels.... )

Some may wonder why I need 1GHz oscilloscope for 100Hz square wave (But really not for SDG1025 any waveform). Of course, depends risetime and how far forward we need go with harmonics and so that they are not attenuated too much.

Pure sinewave is easy, it is only fundamental freq and it is all. 100MHz sinewave need 100MHz oscilloscope (or some over if level accuracy is needed and if scope do not have flat response for stated freq band.)

Every other signal than pure ideal sinewave have harmonics and if we need inspect this some signal using oscilloscope its BW need include all important harmonic frequencies with enough accurate level.

[TunerSandwich]

Square wave is series of sinewaves

Indeed.......with a fundamental, and upper and lower order harmonics....here are two plots with a higher interpolated sample rate.....one showing the dynamic fundamentals of the center frequencies and the other showing the total roll-off of those fundamentals....

I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path

I did the plots posted using coax (properly terminated), but the results will be completely different with a more stable probing solution....and different i/o & measurement settings......to have any kind of real meaning in reality, there has to be a standard/definition of measurement parameters....

maybe I am missing the point of the question?

[EV]

The 4162 is pretty respectable - congrats and enjoy!

Thanks! Here is picture of 40MHz sync out square wave from Tek R7103 scope with 7A29 plugin (BW = 1GHz).

[Wuerstchenhund]

I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path

I agree re. the variability of external parameters like cabling and termination, and that without a proper test setup the screenshots are worthless.

Cables and termination play a huge role which is too often underestimated. Just for fun I repeated some of my measurements with a cheap China crap RG-59U BNC cable I found in a box I was given, and thanks to the mismatch and the overall poor quality of the cable the results were pretty poor. I then put the RG-59U where it belongs (trash can) and re-tested with a Pasternack PE333 SMA cable (rated to 18GHz), and got the same results as with my original measurements (which was done with proper cabling and termination).

It just shows that the best scope (or any other mesurement device) is useless without proper consideration for the measurement path.

maybe I am missing the point of the question?

See it as a bit of fun, i.e. who can produce the worst square wave ever 

[rx8pilot]

I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path

It does show the variables which is specifically what I am interested in learning. Looking at the anomalies and trying to best understand the origin. I agree the screen shots isolated are of limited value, but if the whole setup is described it can be interesting information about what/how signals can be altered by taking a measurement.

[c4757p]

Here is SDS1072CML frequency response.

There's not even a section of that that even remotely resembles "flat".

I'll have to remember that - Siglent wouldn't know a proper analog frontend if it bit them in the ass, apparently.

[TunerSandwich]

See it as a bit of fun, i.e. who can produce the worst square wave ever 

I think I might have some 0.1ohm per foot flat nichrome laying around here....and some BNC to binding post adapters.....maybe I could fashion a split end, moist, wooden stick as the dielectric..... O0

[alterbaron]

There's not even a section of that that even remotely resembles "flat".

I think it looks bad because he's doing a linear frequency sweep.

Here's two plots from LTSpice showing the same 72MHz first-order RC low-pass filter.
The first image looks like your usual flat response up to the corner frequency, followed by the usual 20dB/dec roll-off.
The second image portrays the same data using a linear frequency scale, and it definitely looks less "flat".

[TunerSandwich]

I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path

It does show the variables which is specifically what I am interested in learning. Looking at the anomalies and trying to best understand the origin. I agree the screen shots isolated are of limited value, but if the whole setup is described it can be interesting information about what/how signals can be altered by taking a measurement.

The largest uncertainty will be introduced by the reflections in the cable......unless the gen and scope are utter crap, or we are looking at 100Hz square waves, with massive vertical scales...

Anything useful (by todays standards) is going to suffer the greatest degradation in the cable.....you can see in my plots where the cable capacitance was causing the charge/discharge effect....and subsequent phase shift.

To really resolve such signals, rise time is everything....so we need lots of bandwidth, and active, differential measurements....

My plots were of a 15MHz function @ 10mV....zero offset.  Scope input BW is 600MHz, with a samplerate of 200GS interpolated sinx/x....

As you can see the cable decimated the measurement.....

At a certain point quantum tunneling through silicon will start to become the issue.....it just depends on how deep down the rabbit hole you want to go.....generally we use square waves as a clocking source....so as long as the jitter in the clock chain can still resolve a binary step response it's "all good"......you would be surprised how badly you can mangle a square wave and still not need buffering to resolve a bit

[TSL]

@TunerSandwich that's a mighty fine machine you have there, not often you see an upper limit of 1THz !!

What scope is that ?

regards

Tim

[TunerSandwich]

@TunerSandwich that's a mighty fine machine you have there, not often you see an upper limit of 1THz !!

What scope is that ?

regards

Tim

Hi Tim,

It's a LeCroy WR 64MXi.  Keep in mind that the 200GS is RiS (random interleaved sampling) and the measurement is sin x/x....so there is a great deal of interpolation happening there.  You can see the input noise roll off @ 100GHz (and disappear by 200GHz).  However you can see another ELF fundamental beginning to form.....if we took the timebase out further and were able to maintain that 200GS, we would see the complete ELF fundamental.  Thankfully I know there isn't enough energy present to worry about interference from that tone....but it's amazing that even with the ERES turned off, we can resolve that dynamic range through the noise....I'm quite happy with the scope.

[Wuerstchenhund]

I think I might have some 0.1ohm per foot flat nichrome laying around here....and some BNC to binding post adapters.....maybe I could fashion a split end, moist, wooden stick as the dielectric..... O0

Considering some the things we've seen here I'd say give it a go! 

[rx8pilot]

Silliness aside....

If anyone is willing and technically capable. It would be interesting and informative to show the range of errors between a good scope and SG. Various BNC cables, probes with long and short grounding, good/bad terminations, impedance mismatches, etc.

[TunerSandwich]

Silliness aside....

If anyone is willing and technically capable. It would be interesting and informative to show the range of errors between a good scope and SG. Various BNC cables, probes with long and short grounding, good/bad terminations, impedance mismatches, etc.

The issue we will run into on the SG/FG will be range.....for these modern scopes an old dinosaur just isn't going to give us 10Hz to 1GHz....and a modern Gen that will do that, and still keep quantization noise and step response phase would cost more than most of the scopes we can afford. 

Again seeing perfect square waves isn't that important, in the bigger scheme of things.  They are pulses, and really only useful for clocking.  We can mangle them pretty bad and still resolve a low jitter clock source.....and if that fails we can buffer and oversample to correct potential dynamic range errors. 

I just can't imagine why an utterly pure square wave would be that important.  However, where it might become critical, is in low voltage control signal/clock....but again that can be more easily overcome (than measuring the perfect pulse) by simply oversampling and buffering. 

I will throw a couple more measurements up, that are somewhat practical.  If I have to break out any differential amplifiers and calibrate DC offsets, then it will have exceeded ay kind of real world clock signaling.....a bad PCB layout will utterly destroy rise time, and even a good layout is going to have planar impedance/frequency issues. 

Most real world devices have clock signals, that look even worse than the scope plots in this thread....and still manage to work damn well.....even with shit 5mHZ $0.10 crystals we can get very stable 100MHz clocks......this seems to be one place where software and on chip counters has truly trumped the need for pristine analog square waves. 

What would interest me is seeing just how low of a signal level we could get to, and still derive a clock.....I think even at 1mV pk-pk, with shit interconnects and ludicrous bandwidth we could still pull a clock from (practically) a sine wave.....

Did you see just how bad the ringing was in the plots I posted earlier?  I counted no less than 35 fundamental tones in 1Hz to 100GHz, and that is not even factoring in upper and lower order harmonics.  An interesting experiment would be to feed that garbage back out into a clock ref input of a microprocessor or a/d and see how much jitter it really equals.....and then how much we can clean it up with proper buffering/oversampling.....

[joeqsmith]

Rise time is measured at just over 5ns, which is pretty good. (Bandwidth can be approximated as 0.35 / (rise time), so we can't expect any faster than a 5ns rise on a 70MHz scope.)

I would have guessed that rule of thumb was flushed down the toilet long ago. 

[tautech]

Silliness aside....

If anyone is willing and technically capable. It would be interesting and informative to show the range of errors between a good scope and SG. Various BNC cables, probes with long and short grounding, good/bad terminations, impedance mismatches, etc.

I tried to display some in post:
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg588472/#msg588472

Sure it is with only 10 MHz, but there is 4 differing connections:

RG-58C/U 50 Ohm source & DSO internal termination
RG-58C/U 50 Ohm source & Tek 50 Ohm feed-through
Hi Z source 10x probe
Hi Z source 1x probe
Both probes into DSO 1M of course. 

Any further requests? 

[Jay_Diddy_B]

Hi group,

We can look to simulation to get an idea of the waveforms we should expect from various combinations of pulse generators and scopes.

I have created a LTspice model that has 200ps and 5ns risetime pulse generators. I have added some 50 Ohm (RG58 type transmission lines) and 75 Ohm transmission lines (RG59 type) The 10ns length represents about 2m of cable.

I have also generated 20 and 50 MHz Bessel and Butterworth filters. The Bessel filters would be the best choice for square waves, the Butterworth filters would give better sinewave performance.

I have also added a (near) Gaussian filter with 100MHz to simulate a traditional oscilloscope response. A modern oscilloscope might not have a Gaussian response.

Here is the model:



And the results:












I have attached the LTspice model in a zipfile.

Regards,

Jay_Diddy_B

*** This is my 666 th. message ***

[tautech]

*** This is my 666 th. message ***

[T3sl4co1l]

*** This is my 666 th. message ***

And that one (or at least you're showing it at this instant) was your 1669th... say what you will?  

[Rupunzell]

There is a divide between the importance of pulse fidelity between analog folks and digital folks.

For digital folks, accurate, reliable, consistent transmission and reception of ones or zeros is what matters most. As clock rates and data rates have gone well into the Ghz range common practice and techniques from the RF-microwave world have been incorporate into much of modern digital design. Varying degrees of pulse distortion is often acceptable as information is transmitted as basic on or off over time.

Pulse, transient fidelity can be quite different for all that analog stuff as impulse response can tell a LOT about circuit and system behavior when test like this are applied properly and interpreted properly. Doing this really, really well require a great deal of theoretical and real world experience.

 If one were to dig into the entire field of pulse fidelity, transmission lines, impedance matching and all related there were a number of Tektronix & Hewlett Packard application notes published back in the 1960 and 1970's that does a good job at explaining this along with  text books materials. Little if any of that physics has changed to this day. The foundations of this technology remains much the same.

What could be more relevant in this discussion of pulse response and all related has been covered in a Linear Technology app note# 47 written by Jim Williams in 1991.
http://cds.linear.com/docs/en/application-note/an47fa.pdf

The moment a probe or interconnecting cable has been attached to a DUT  to examine and gather information about it's behavior with a time or frequency domain instrument, the actual DUT behavior can be easily skewed and distorted if all involved is not properly understood and applied.

As for old dinosaur pulse generators not being able to go from 10 Hz to 1Ghz.. Not really true, there are quite a number of snap diode, tunnel diode pulse generators that can easily cover 10 Hz to over 1 Ghz with low noise from the 1960's. It is so easy to forget and discount what has been done and replace it with what is the latest and greatest, part of the not invented here syndone. All instrumentation is relative to need and expectations limited by humanity's current understanding of physics.



Bernice

[TunerSandwich]

As for old dinosaur pulse generators not being able to go from 10 Hz to 1Ghz.. Not really true, there are quite a number of snap diode, tunnel diode pulse generators that can easily cover 10 Hz to over 1 Ghz with low noise from the 1960's. It is so easy to forget and discount what has been done and replace it with what is the latest and greatest, part of the not invented here syndone. All instrumentation is relative to need and expectations limited by humanity's current understanding of physics.

Bernice

The problem there is assuming they are still in spec....and then having an order of magnitude higher resolution signal chain, to even answer that question. 

Believe me I am not saying there is NO merit to hi-fidelity analog pulse measurements.....but in a DSO world, and a world filled with oversampling and "cheap" clocks....the quest for fidelity becomes somewhat of an academic endeavor. 

It's all good sport, but I highly doubt a bean counter overlooking a project is going to justify the cost of going down that road, when there are so many "band-aids" post A/D to "clean up" those potential "problems". 

It's one of those things where we've just gotten too deep into the band-aid approach and all the signals are good for is proving or disproving some theoretical ideal.  I would think the more relevant test today is an artifact based PWM signal, which has coincidental parameters to the way in which a DSO acquires, and then interpolates/represents a signal. 

This is one of those few occasions where I would discount the overall fidelity of an analog pulse, and it's usefulness as a reference.  Maybe that's not a good thing, but one does have to admit it's at least a valid reality?   

P.S. I have never bought into the digital vs analog statement.....at the end of the day it's all still analog....the 0s and 1s have to ride on something right?    There just happens to be a lot more room for "error" in that application

[c4757p]

*** This is my 666 th. message ***

And that one (or at least you're showing it at this instant) was your 1669th... say what you will?  

2669?

[AlfBaz]

Rise time is measured at just over 5ns, which is pretty good. (Bandwidth can be approximated as 0.35 / (rise time), so we can't expect any faster than a 5ns rise on a 70MHz scope.)

I would have guessed that rule of thumb was flushed down the toilet long ago.

Is this true?

I recall looking at this with simulations, some time ago.

Given the unity gain bandwidth specifications of LT opamps and their available models in ltspice, I firstly checked their bandwidth with ac analysis, used the -3db point to determine the rise time using that approximation then fed different pulses above and below the calculated figure to observe differences in output responses to the input pulse and got good correlation

[T3sl4co1l]

*** This is my 666 th. message ***

And that one (or at least you're showing it at this instant) was your 1669th... say what you will?  

2669?

Damn, the only thing missing is you needing 6996 posts.  (You broke it!)  Remind me of this thread in a few weeks / months, would you?

Tim

[Jay_Diddy_B]

Hi group,

I want to extend my previous post with some measurements.

I apologize for the blurry pictures.

I want to show just how bad the cable can be:

Here is a reference waveform made with a 50 Ohm cable. The scope bandwidth is 1 GHz and the HP8112A pulse generator has 4.5ns rise and fall times.





I then replace the cable with a really bad cable made from 75 Ohm RG6 coax with binding post adapters for the connections:

Here is the waveform:



It is similar to the waveform from the LTspice model. The notch on the leading edge is twice the time it takes for the signal to travel from one end of the cable to the other. The velocity is 66% of the speed of light.



Here is a photograph of the (terrible) construction of the cable.



If I increase the rise and falltimes to 10ns (greater than or equal to the electrical length of the cable) most of the distortion caused by the impedance miss match are eliminated.



So generally the impedance matching is important if the risetime is less than the propagation time.

Regards,

Jay_Diddy_B


 

[BravoV]

So generally the impedance matching is important if the risetime is less than the propagation time.

Thanks, its written in my personal notebook now ! 

[rx8pilot]

I tried to display some in post:
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg588472/#msg588472
..............
Any further requests? 

Thank you for that.

I then replace the cable with a really bad cable made from 75 Ohm RG6 coax with binding post adapters for the connections:
Here is the waveform:

I was expecting worse from the binding post contraption.

[Jay_Diddy_B]

Hi,

Let me take to extremely bad cables. Lets us try 2m (6.5 ft) of lamp cord 2 x 18 awg:



At 10 MHz with 4.5ns rise and fall times you can see several reflections in the cable:



With the frequency changed to 2 MHz and the rise and fall time increased to 30ns the waveform doesn't look too bad:




I have posted these to reinforce the concept that the impedance is less important if the propagation time is less than the rise time.

Regards,

Jay_Diddy_B

[katzohki]

I wonder if we could glean any interesting information from this discussion in terms of the frequency domain...

I'm picking up an HP 8116A and HP 8904A on Friday so I'll try to post some pics coming Monday. Someone already posted with the 8116A, it looked pretty good I think.

[T3sl4co1l]

I wonder if we could glean any interesting information from this discussion in terms of the frequency domain...

I'm picking up an HP 8116A and HP 8904A on Friday so I'll try to post some pics coming Monday. Someone already posted with the 8116A, it looked pretty good I think.

Certainly can: the time and frequency domains are dual: complementary and inverse.  Shorter risetime means higher bandwidth; wave shape is determined by harmonics (fundamental frequency * N), while envelope shape (e.g., AM modulation) is determined by sidebands (fundamental frequency +/- X), the rate of which corresponds to the difference and so on.

Because of this dual property, one can use the time domain response to derive an equivalent RLC circuit (assuming certain conditions), just as one can use the frequency domain response.

Tim

[joeqsmith]

Rise time is measured at just over 5ns, which is pretty good. (Bandwidth can be approximated as 0.35 / (rise time), so we can't expect any faster than a 5ns rise on a 70MHz scope.)

I would have guessed that rule of thumb was flushed down the toilet long ago.

Is this true?

What do the specs show for DSOs made in the last 10 years?   

[Hugoneus]

I'll play. How is this?  O0

[rx8pilot]

54ps...nutz.

I think the 8Ghz instrument sees a lot.

[tautech]

54ps...nutz.

I think the 8Ghz instrument sees a lot.

That is on no way the impressive stat........2.5 GHz square wave.   

I think you win  Hugoneus

[rx8pilot]

That is on no way the impressive stat........2.5 GHz square wave.   

I guess that is reasonably quick.
Now I am curious what 6g/bps HD-SDI looks like at 100 meters. That would stress even that fancy Agisight scope.

What generated the 2.5 Ghz and how was that signal delivered to the instrument?

[miguelvp]

54ps...nutz.

I think the 8Ghz instrument sees a lot.

That is on no way the impressive stat........2.5 GHz square wave.   

I think you win  Hugoneus

I don't know.... I think I see some Jitter, maybe it has a non locking PLL


If the wink is not enough, I kid 

[Yago]

Hehe, Shahriar entered the thread like Clint Eastwood in a Fist Full of Dollars!

[T3sl4co1l]

Hehe, Shahriar entered the thread like Clint Eastwood in a Fist Full of Dollars!

Well, considering halfway up the thread, others have posted their 30ps waves from SD-21 or whatever they are TDR rigs...

Tim

[TunerSandwich]

I think some tests with controlled impedance lines would really be in order here.  I still think it's a bit of a pissing contest, or at least doesn't have much practical application.....but I can see the fun in it. 

I dug out some spools of NiCr, Kanthal A-1 and some of our own proprietary Ti resistance wire.....using these as a basis for conductors, might lend some insight into how VERY controlled impedance changes these measurements, as well as how the tempco changes measurements....especially as the transmission lines polarize and saturate.....

Maybe, just for fun, throwing some controlled capacitance into those transmission lines would also lend to some insights....

I think i have some PTFE jacketing laying around, as well as some shielding braid.....but that might start getting a bit carried away.....

I will build up some controlled impedance transmission lines....with no shielding, and limit the freq.....to hopefully show that conductor impedance mismatches skew these measurements more than just about anything....and RF inductance be damned 

I have personally never done that experiment, but I think theory is well established/sound....I am curios to see how sub ohm discrepancies between conductors skew the measurements.....especially with low energy signals....

any suggestions or ideas on what resistance offsets to attempt?  what amplitude signal?  timebase/freq?  etc....

I think I can build up some pretty "bad" cables here....and see just how far we can decimate a square wave.....

[T3sl4co1l]

Sure, that's easy enough to do...



The subject: 50' of lamp cord.  BNC to binding posts on either end.

Oh, and just for kicks, I connected one end backwards.



Didn't even bother with the fast risetime on this one; the bounce is obvious.  It's also unterminated.  Overshoot suggests Zo ~= 100 ohms, which is typical for twisted pair and the like.

On the faster rise time, I get 55ns rise terminated, 28ns unterminated.

Due to the twist, at lower frequencies, the square wave tilts down towards ground, as if shunted by an inductance, because... it is.

Another good exercise is to take a 10x probe near sub-10ns edges and see what probing does.  Without any ground clip at all.  You may be pleasantly surprised by the outcome!

Tim

[TunerSandwich]

Yes, but that is copper.....the NiCr or A=1 our our own fancy Ti resistance wire would be a lot of fun, because the polar offset can be controlled to around 0.1ohm per foot.....

I am curious to see if the scope can resolve a 0.5ohm or lower offset, through 50 ohms.....with let's say a 10mA 1K pulse....

Also can we rectify some of the sine waves that make up the pulse (with no diode ICs), and actually get a series of pulses within the pulse....

I am curious about what saturation level in the Ti wire (especially) will lead to some feedback, and introduce some controlled oscillations

Worlds crudest digital multiplexer? Or just a shitty theory? 

[Yago]

Hehe, Shahriar entered the thread like Clint Eastwood in a Fist Full of Dollars!

Well, considering halfway up the thread, others have posted their 30ps waves from SD-21 or whatever they are TDR rigs...

Tim

Yes, sorry it was my light hearted frivolity, and lack of understanding in this area.
Didn't mean a disservice to the thread.

[Hugoneus]

Hehe, Shahriar entered the thread like Clint Eastwood in a Fist Full of Dollars!

Well, considering halfway up the thread, others have posted their 30ps waves from SD-21 or whatever they are TDR rigs...
Tim

Yes, sorry it was my light hearted frivolity, and lack of understanding in this area.
Didn't mean a disservice to the thread.

Alright, alright... How about an 81Gb/s circuit I made a while back with a rise time of 5.2ps?  O0

Measured using an Agilent 70GHz remote heads on a sub-sampling scope, on wafer with 1mm probe and cables.

[G0HZU]

In theory at least, I think that the characteristic impedance of the transmission line becomes irrelevant at certain cable lengths if the squarewave is continuous. Because a square wave is made up of a series of sine waves of F, 3F, 5F, 7F etc etc then the characteristic impedance of the line doesn't matter if the line is (for example) 180degrees long at F.

So if you had a (continuous) square wave that had a very fast risetime then you can still get a good square wave if the line is 180 degrees at frequency F. So in theory you can break the risetime vs propagation time rule if the cable is a certain length (or multiples of this length).

In reality, a typical transmission line will not behave as ideally as this but at high clock frequencies it might be worth experimenting with the length of the cable  at the clock frequency F. A good length to try is 180degrees at the clock frequency.

I still think it's a bit of a pissing contest, or at least doesn't have much practical application.....

Agreed. It does all seem a bit silly. The fastest pulse generator I have here was made in the 1970s and cost me £5 and that has been good enough for me for the last 20years or so

[TunerSandwich]

In theory at least, I think that the characteristic impedance of the transmission line becomes irrelevant at certain cable lengths if the squarewave is continuous. Because a square wave is made up of a series of sine waves of F, 3F, 5F, 7F etc etc then the characteristic impedance of the line doesn't matter if the line is (for example) 180degrees long at F.

So if you had a (continuous) square wave that had a very fast risetime then you can still get a good square wave if the line is 180 degrees at frequency F. So in theory you can break the risetime vs propagation time rule if the cable is a certain length (or multiples of this length).

In reality, a typical transmission line will not behave as ideally as this but at high clock frequencies it might be worth experimenting with the length of the cable  at the clock frequency F. A good length to try is 180degrees at the clock frequency.

I still think it's a bit of a pissing contest, or at least doesn't have much practical application.....

Agreed. It does all seem a bit silly. The fastest pulse generator I have here was made in the 1970s and cost me £5 and that has been good enough for me for the last 20years or so

Yes indeed....I posted on page 11 (some screenshots) showing this exact concept.  You can clearly see that the 15MHz square is made of over 35 discreet tones between DC (ok ok not DC, but I can't be bothered to go back and look at that....let's call it 0.1HZ) and 100GHz.  The rolloff was sharp past that, but the signal tones went out past 800GHz.  I did this measurement @ 200GS/sec (R.I.S.) and sin x/x interpolation....so the details aren't wholly trustworthy.....but do follow theoretical observations. 

I suggested using resistance wire to build some cables, because then we can make some accute predictions and observations....that have a basis in a measured set of benchmarks.  I.E.  what it the transmission line impedance discrepancy (closed loop) was a precise 0.1 ohm per foot?  At some point I am not going to sit here and laser trim the cable ends, but at least that is a ballpark measurement, and we aren't guessing about the impedance discrepancies from +/-.....

Bigger question though....would the scope even be able to resolve that offset, through it's own 50ohm shunt? And even then I wonder how much impedance discrepancy the actual sig gen out and scope in has (closed loop).  If we knew that, then we could derive a theory about how to swing and shape our pulses....

I suggested resistance wire, because it has a saturation point and I believe it will act as a diode at a certain point (zener effect).  I just think it would be hilarious to build a cable that rectified some of the square wave (sine) tones......It would be fun to see a square within a square, and turtles all the way down to the step response of the scope.....

[photon]

Hehe, Shahriar entered the thread like Clint Eastwood in a Fist Full of Dollars!

Well, considering halfway up the thread, others have posted their 30ps waves from SD-21 or whatever they are TDR rigs...
Tim

Yes, sorry it was my light hearted frivolity, and lack of understanding in this area.
Didn't mean a disservice to the thread.

Alright, alright... How about an 81Gb/s circuit I made a while back with a rise time of 5.2ps?  O0

Measured using an Agilent 70GHz remote heads on a sub-sampling scope, on wafer with 1mm probe and cables.

Shahriar,
This is fast. Is it silicon or some exotic semiconductor? What geometry? The speed of this clock (81Hz or 12.35ps) is faster than any I am familiar with. Can you share some implementation details?

[Hugoneus]

Shahriar,
This is fast. Is it silicon or some exotic semiconductor? What geometry? The speed of this clock (81Hz or 12.35ps) is faster than any I am familiar with. Can you share some implementation details?

This is an 81Gb/s TIALA-Retime in 65nm GP CMOS process. It uses a full rate clock, so 81GHz clock. You can see it here:

http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?arnumber=4674506

Cheers,

[photon]

Shahriar,
This is fast. Is it silicon or some exotic semiconductor? What geometry? The speed of this clock (81Hz or 12.35ps) is faster than any I am familiar with. Can you share some implementation details?

This is an 81Gb/s TIALA-Retime in 65nm GP CMOS process. It uses a full rate clock, so 81GHz clock. You can see it here:

http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?arnumber=4674506

Cheers,

Thanks for sharing your knowledge, much appreciated.

[T3sl4co1l]

Yes, but that is copper.....the NiCr or A=1 our our own fancy Ti resistance wire would be a lot of fun, because the polar offset can be controlled to around 0.1ohm per foot.....

The wha..?

I am curious to see if the scope can resolve a 0.5ohm or lower offset, through 50 ohms.....with let's say a 10mA 1K pulse....

Well, 0.5 ohm will add 1% of droop, roughly speaking.  Whether high or low frequencies are attenuated more, I'm not sure offhand how that factors in.

Also can we rectify some of the sine waves that make up the pulse (with no diode ICs), and actually get a series of pulses within the pulse....

I am curious about what saturation level in the Ti wire (especially) will lead to some feedback, and introduce some controlled oscillations

Tim

[TunerSandwich]

Tim

The resistance wire will saturate, and act like a diode.....and rectify some of the sinewaves in the pulse (zener effect)....can't be bothered to do the math to see if that will be in the bandwidth limitations of the original signal. 

I have done a lot of experimentation with those scenarios (part of what we do in my business) and most resistance wire will saturate to the point of oscillating loud enough to hear it (and that is just with DC).  Although I am not keen to dump 60 amps into my scope 

However if it rings loud enough to hear it at 60 amps, then I am most certain it rings at inaudible frequencies, with significantly less power. 

I will build up some cables out of this stuff and we can see if any of that proves to be true, with small signals......

Think ribbon tweeter.....

[T3sl4co1l]

I... don't think you know the definitions of those words...

Saturation is a characteristic of ferromagnetic and ferroelectric materials.  Resistance wires are almost never ferromagnetic.

Saturation has no effect on DCR (or, extremely little).

Saturation does not "act like a diode".

The zener effect is extremely specific: the breakdown of a narrow semiconducting junction due to tunneling current.  It does not appear in the physics of ferroelectrics or ferromagnetics.

Saturation is not oscillation, and oscillation is not DC.  Whatever instability you're talking about, it isn't related to any of the words you're using...

Ribbon tweeters use very well understood principles of electromagnetic induction and do not involve concepts of saturation, rectification, zener breakdown, or oscillation (aside from the intentional influence of acoustic waves).  The magnetic field in the device may be designed with ferromagnetic components, but this is not necessary (an admittedly very inefficient ribbon mic could be constructed with electromagnets and no ferromagnetic components).

Tim

[joeqsmith]

Rise time is measured at just over 5ns, which is pretty good. (Bandwidth can be approximated as 0.35 / (rise time), so we can't expect any faster than a 5ns rise on a 70MHz scope.)

I would have guessed that rule of thumb was flushed down the toilet long ago.

Is this true?

What do the specs show for DSOs made in the last 10 years?   

From Tektronix

Question:
How is bandwidth related to rise time for oscilloscopes?
Answer:

Historically, oscilloscope frequency response tended to approximately follow the rule: Bandwidth x risetime = 0.35. This corresponds to a 1- or 2-pole filter roll-off in the frequency domain. Today, at the high end, most real-time digital oscilloscopes more closely follow this rule:

Bandwidth x rise time = 0.45.

This corresponds to a much steeper frequency roll-off above the specified bandwidth. The steeper roll-off is more desirable in digital oscilloscopes that oversample by 4x, 3x, or even less because it prevents aliasing by eliminating any signal above the Nyquist frequency (1/2 the sample rate – the minimum sample rate required for accurate signal representation).

From Teledyne

Risetime-Bandwidth Product (RT*BW)
Typically RT*BW = 0.40 to 0.45 for modern high bandwidth scopes
Historically analog scopes RT*BW = 0.35

[TunerSandwich]

Saturation is a characteristic of ferromagnetic and ferroelectric materials.  Resistance wires are almost never ferromagnetic.

Tim

Nope....yer dead wrong on that one....most resistance wire has enough iron in it to do exactly what I described.  I work with the stuff everyday, and have done these experiments more times than I care to recall.  We'll build up those cables and see what happens....

[LabSpokane]

That wire might be magnetic, but if it's acting like a diode it's because of corrosion, not magnetic saturation. Colloquial terms include "rusty bolt effect" and "rusty fence effect". In radio it's called passive intermodulation.

http://en.m.wikipedia.org/wiki/Rusty_bolt_effect

[TunerSandwich]

That wire might be magnetic, but if it's acting like a diode it's because of corrosion, not magnetic saturation. Colloquial terms include "rusty bolt effect" and "rusty fence effect". In radio it's called passive intermodulation.

http://en.m.wikipedia.org/wiki/Rusty_bolt_effect

Now that is something I am willing to believe. Most of these wires oxidize almost immediately and we spend a lot of time cleaning them before lacquering. I have a spool of some quite well corroded A-1 laying around. I will build up two sets of cables, one cleaned and one dirty and lets see what happens.

[Electro Fan]

I'm way behind you guys finding all sorts of more advanced and interesting things but I thought I'd try to see how much impact scope technology and bandwidth impact the end to end results.

Below is the same 20 MHz square wave on a 70 MHz Rigol digital scope and a 400 MHz Tektronix analog scope - some difference but not a ton of apparent difference.

[Electro Fan]

Hi group,

I want to extend my previous post with some measurements.

I apologize for the blurry pictures.

I want to show just how bad the cable can be:

Here is a reference waveform made with a 50 Ohm cable. The scope bandwidth is 1 GHz and the HP8112A pulse generator has 4.5ns rise and fall times.





I then replace the cable with a really bad cable made from 75 Ohm RG6 coax with binding post adapters for the connections:

Here is the waveform:



It is similar to the waveform from the LTspice model. The notch on the leading edge is twice the time it takes for the signal to travel from one end of the cable to the other. The velocity is 66% of the speed of light.



Here is a photograph of the (terrible) construction of the cable.



If I increase the rise and falltimes to 10ns (greater than or equal to the electrical length of the cable) most of the distortion caused by the impedance miss match are eliminated.



So generally the impedance matching is important if the risetime is less than the propagation time.

Regards,

Jay_Diddy_B

I was away from the thread for a while - Jay_Diddy_B your posts are very cool.

Just to clarify, when you say propagation time are you speaking of the time it takes the signal to leave the generator and reach the scope (ie, based on the length of the cable), or something else? (Hope I got that right or I am going to incur some laughter  )

[Electro Fan]

Just one other semi-related observation - I find that scopes and other test equipment (including frequency/function generators and frequency counters) seem to consistently do well with frequency counting accuracy but struggle a little more with accurate voltage measurements (or perhaps this might just be due to my limited experience).  Further, it would seem that both frequency and voltage measurements are needed to calculate rise time. 

All that said, and no doubt cabling quality and cabling length along with impedance mismatching can have some impacts, it would seem that a generator's ability to produce good rise times (and fall times) is among the key determinants of the ability to produce a nicely square square wave.  Yes, no?

[TunerSandwich]

[T3sl4co1l]

And those frequencies are due to the wire, you say?

[Howardlong]

And those frequencies are due to the wire, you say?

Some folks get paid to make antennas like that.

[TunerSandwich]

And those frequencies are due to the wire, you say?

Some folks get paid to make antennas like that.

I will sell you this antenna for less than they will

[TunerSandwich]

 

[TunerSandwich]

And those frequencies are due to the wire, you say?

? that's at 10mV?  I doubt the wire is doing anything, other than acting as an antenna.....the pulse is buried in there somewhere.....

[TunerSandwich]

now watch what this wire does, as the power increases......this is 1Mohm termination.....the resistance wire is pretty closely matched to 4ohm per conductor (you can see in the waveform).

[TunerSandwich]

[TunerSandwich]

Here is the Titanium resistance wire my company makes....it contains no iron, nickel, manganese, chromium or aluminum/copper.  These conductors are matched to 2.5 ohms each. 

Same setting on the sigGen, same 1Mohm termination

[T3sl4co1l]

Both look about like what you'd expect from a mismatched transmission line of that length.

Tim

[TunerSandwich]

So do I win for the worst square wave possible?  Someone told me that was the point of this thread, back on page 11 or 10 ( )

[LabSpokane]

You win the prize. Absolutely no doubt about that. 

[Pjotr]

A 45 years old article about probing:
http://www.ece.vt.edu/cel/docs/TekProbeCircuits.pdf

Also worth reading this Agilent app note:
http://cp.literature.agilent.com/litweb/pdf/5990-8371EN.pdf

Maybe it becomes clear why el cheapo Chinese probes supplied with the lower end DSO's are not the ones to get most out of what these scopes are capable of regarding pulse response. And sometimes "lie" a bit.

[joeqsmith]

Pulse output feeding the two  "T"s back to back to from an "H"   One  output of the H drives the scopes input.  The remaining two have a fair amount of coax forming a loop.    Normally used for benchmarking the DSO, in this case shows how power is split between the loop and the DSO's input.  Once the power from the loop shows up, the voltage is doubled.     If the loop were long enough, you would see a second pulse (with VERY low phase noise compared with the exciter pulse.   



Nice Agilent scope Hugoneus!   

[DIPLover]

10, 20 and 40MHz square waves from Altera Stratix FPGA Enhanced PLL to Tektronix 2465. CMOS 2.5V IO standard.

The old boat anchor is still beating specs (a little) 30 years after being built (and 10 years after last pro calibration sadly  )

Just received today my Rigol DS2072A, fully unlocked to 300MHz bandwidth. Here are the results of the same measurements with identical setup.

Rise time @ 40MHz is a bit worse than the venerable Tek 2465 but quite respectable. With all the fantastic DSO capabilities, this will be a worthwhile companion to the old clunker I believe.

[-jeffB]

Alright, alright... How about an 81Gb/s circuit I made a while back with a rise time of 5.2ps?  O0

Oh, come on. There HAS to be SOMEONE around here doing millimeter-wave work...

[katzohki]

To get back on topic, here is a comparison between two different function generators, both running at 50kHz. You can clearly see that, yes indeed there is a difference in the shape "quality" between them. Both are 50 ohm terminated.

First a HP 8116A:


You can see that the square wave is a very tight shape and has rise time of 6.3ns.

Next the HP 8904A:

The edges are more rounded and the rise time is ~1.7us.

You can see a good bit of difference between them. The HP 8116A is a 50MHz generator and will, in my opinion, still output a good square wave up into 25MHz or so. The HP 8904A, on the other hand, is rated at 0-600kHz for sine and 0-50kHz for square (and ramp / triangle) so it is working at its absolute upper limit. They both are very nice units and the HP 8904A is particularly versatile, but you can see that each has its application and yes indeed not all FGs are made alike.

PS: I posted a review of the HP 8904A on my blog (shameless plug) in case you might be interested and I'm planning one on the HP 8116A as well. http://katzelectronics.blogspot.com/2015/01/hp-3904a-review.html Just in case you might be interested. 

PPS: Ignore the 2kV/div on channel one. I normally have a 1000:1 scope probe on that channel and was too lazy to change it. 

[Teneyes]

I see Rigol DSO displays are being posted on this thread and comments about overshoot.
I wish to inform All the effects of the SinX/X interpolation on the sample data for Rigol DSOs
In the displays below I used My DS2000 to show a Perfect 62.5MHZ square wave Sampled at 2 GSa/s

1st display shows the sample data in Dot Mode , perfect step transistions.
2nd display shows how the Sinx/X process is implemented on the Rigol DS2000, and shows ringing!
Owners need to be aware of this at Faster scan rates, where sample data count is low for the displayed area

a bit OT
Also someone commented that pulses are mainly used for clocking.
in the 3rd display I show how a pulse train can produce a Spread Spectrum of frequencies
for bandwidth testing.  The duality of Time and Frequency Domains

[tautech]

I used My DS2000 to show a Perfect 62.5MHZ square wave Sampled at 2 GSa/s

Source?

[tautech]

Source?

NO source!,
I was leading you on,
I saved a waveform data ,
I then Patched the Data. to values to show a step change.
I then loaded it back into the DSO. 

I thought everyone could see it was too prefect.

I figured as much  and know now to watch out for any waveforms you might post. 

[joeqsmith]

Square wave is series of sinewaves

Indeed.......with a fundamental, and upper and lower order harmonics....here are two plots with a higher interpolated sample rate.....one showing the dynamic fundamentals of the center frequencies and the other showing the total roll-off of those fundamentals....

I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path

I did the plots posted using coax (properly terminated), but the results will be completely different with a more stable probing solution....and different i/o & measurement settings......to have any kind of real meaning in reality, there has to be a standard/definition of measurement parameters....

maybe I am missing the point of the question?

A saw your post some time ago.  You brought up some good points.   You stated the DSO you used for this data was a WR64MXI with 600MHz BW with a 15MHz input using coax.    I did not understand the THz FFT but thought I would try and replicate your results.

I am using my Sony AWG2041 to generate a 15MHz squareware with roughly the same amplitude as you show.  This generator has a little sharper edges.  I am using Thermax RGU-400 with SMAs torqued to 8"/lbs.   ARB uses crappy BNCs, so I have a BNC to SMA for this test.   My DSO is an older Wavemaster 8500A, 5GHz.     

As I would expect, the FFT drops like a rock well before I reach 10G.    Amazing how different the two setups behave. 





 

     

[joeqsmith]

Same setup but with an crappy RF generator attached with 3.8GHz signal.   



20Gs/s with 50ohm MWM terminator attached.  -92dBm. 

[Electro Fan]

How should these colors be interpreted - what do they signify or represent?  Thanks

[Jay_Diddy_B]

Hi,

I had a look at this picture:



I can explain it. The square wave is 15 MHz, so the spectral lines in the FFT should be 15MHz apart. From the shape of the waveform I would expect to see the higher order harmonics attenuated.

The FFT shows spectral lines that are 5 GHz apart. This is sampling frequency of the scope 5G samples per second. The Lecroy scope is using RIS acquisition.

Regards,

Jay_Diddy_B

[Wuerstchenhund]

How should these colors be interpreted - what do they signify or represent?  Thanks

The picture is a 3D color persistence screen, which is essentially a more advanced variant of the common 2D persistence function many scopes have today.

Most scopes have a monochrome persistence function (i.e. intensity grading) where individual waveforms overlap each other on a single "depth" layer (the screen plane) and where the brightness represents the amount of times a waveform has passed through a particular spot on the screen. This can be used (in limits) to see jitter or other signal anomalies. More advanced scopes use color grading, i.e. the color shows how often a waveform has passed through a particular spot, where red ('hot') shows places of high occurrence, yellow for medium occurrence and blue for low occurrence.

In a 3D persistence screen each waveform is 'stacked' on top of the other, which shows much better how the waveforms change over time. Again, the colors indicate the occurrence of a waveform passing through a certain spot in the horizontal (x/y) plane.

It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.

[T3sl4co1l]

Or to put it another way, it's a histogram of the waveform hitting those x,y (time/voltage, frequency/amplitude) points.  If you set up an external clock trigger and play random data, you automatically get your eye diagram that way.

Tim

[Kibi]

I have the results from two generators. One is a GW Instek SFG-2110 (10MHz bandwidth). The second will the from the built in wavegen function of my Agilent DSO-X 2002A (10MHz bandwidth).

First up: GW Instek SFG-2110

1MHz


5MHz, jitter is starting to creep in.


5MHz, with averaging switched on.


10MHz, at full chat now and jitter is quite bad.


10MHz, with averaging.




Next up is the DSO-X 2002A built in wavegen option. This seems to have better jitter performance, but not as good with the high frequency harmonics.

1MHz


1MHz with averaging


5MHz


5MHz with averaging


10MHz, full chat. I checked and it is still supposed to be outputting a square wave.


10MHz with averaging

[TunerSandwich]

It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.

It shows just how much the measurement device itself can influence the result....RIS + sinX interpolation + 3d persistence.....really shows just how many artifacts can be attributed to the WAY in which a device interpolates what it's being fed.....I wanted to show just how far away we can get from something "trustworthy", especially when sampling and interpolating a signal....I wish the scope had an AES/EBU input and I could lock it to an external sample clock (via word clock sync).....I would love to see how a pure digital interpolation of a synthesized signal is skewed by the scopes DSP/processing engine.....

I have a cool V.A.S.T synthesis engine here, that can build block chains of various types of modulations and sources (thanks Ray Kurzweil).  Sadly I think the d/a a/d and "analog" cable run would skew the results beyond the ability to make any solid predictions about HOW the scopes own interpolation transforms the original source.....(the synth has a digital out, but the scope doesn't have the corresponding input....I don't have the proper accessory)

Producing a model of a square wave, should be a very straight forward endeavor.....but everything in between that model and the way it's interpolated to the screen of a discreet device makes the whole concept quite a bit more "complicated".....in the "analog world" we live in....square waves just don't seem to want to exist.....and nature seems to like to avoid straight lines....

The real world is quite a complex place.....the virtual world is so much more simple.....shows just how far off we are of the vastness and complexity of the natural world....sometimes I step back and think we are still "living in caves"

somehow through all the muck we still manage to send 0 and 1 through global interconnection systems....most of which use far "shoddier" cabling solutions than we are displaying here (with lots of band-aids on them)....

kind of trying to re-enforce my earlier point, that showing square waves, even between "premium" gear is a rather pointless.....as it's very difficult to attribute exactly where the non linearities are coming from....are they induced (EM), are they processing "errors" etc etc etc....I could see one spending vast resources to produce a "perfect" square wave....only to realize it has no real practical application

 


it really is turtles all the way down

[TunerSandwich]

Square wave is series of sinewaves

Indeed.......with a fundamental, and upper and lower order harmonics....here are two plots with a higher interpolated sample rate.....one showing the dynamic fundamentals of the center frequencies and the other showing the total roll-off of those fundamentals....

I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path

I did the plots posted using coax (properly terminated), but the results will be completely different with a more stable probing solution....and different i/o & measurement settings......to have any kind of real meaning in reality, there has to be a standard/definition of measurement parameters....

maybe I am missing the point of the question?

A saw your post some time ago.  You brought up some good points.   You stated the DSO you used for this data was a WR64MXI with 600MHz BW with a 15MHz input using coax.    I did not understand the THz FFT but thought I would try and replicate your results.

I am using my Sony AWG2041 to generate a 15MHz squareware with roughly the same amplitude as you show.  This generator has a little sharper edges.  I am using Thermax RGU-400 with SMAs torqued to 8"/lbs.   ARB uses crappy BNCs, so I have a BNC to SMA for this test.   My DSO is an older Wavemaster 8500A, 5GHz.     

As I would expect, the FFT drops like a rock well before I reach 10G.    Amazing how different the two setups behave. 





 

   

your cabling solution is vastly superior to the one I used....(I used the coax that came with the rigol 2102a/s)

In the original post the statement was put forth....use the maximum "horsepower" of your scope to display a square wave.....just trying to show how misleading that can really be.....

It is amazing how different the results are, between the two devices.....no doubt about that....I would argue that you have the superior scope for this kind of test.....?

[Pjotr]

kind of trying to re-enforce my earlier point, that showing square waves, even between "premium" gear is a rather pointless.....as it's very difficult to attribute exactly where the non linearities are coming from....are they induced (EM), are they processing "errors" etc etc etc....I could see one spending vast resources to produce a "perfect" square wave....only to realize it has no real practical application

 


it really is turtles all the way down

Well, there is at least one turtle that benefits from a near perfect square wave source: Adjusting your high impedance HF probes as good as it gets

[TunerSandwich]

I personally thought this was the most interesting signal i had posted....the square wave is still in there, amongst the garbage of the antenna

[TunerSandwich]

also this.....look at the timebase    where exactly is that "squarewave" coming from.....it sure as hell ain't the sigGen....I got a good laugh out of it anyhow

[TunerSandwich]

kind of trying to re-enforce my earlier point, that showing square waves, even between "premium" gear is a rather pointless.....as it's very difficult to attribute exactly where the non linearities are coming from....are they induced (EM), are they processing "errors" etc etc etc....I could see one spending vast resources to produce a "perfect" square wave....only to realize it has no real practical application

 


it really is turtles all the way down

Well, there is at least one turtle that benefits from a near perfect square wave source: Adjusting your high impedance HF probes as good as it gets

yes, no doubt about that....which I suppose has some VERY useful application.....when looking at impulse responses and the potential phase issues....touche'

[EV]

I see Rigol DSO displays are being posted on this thread and comments about overshoot.

Here are pictures you asked:

Generator: Rigol DG4162, sync out, 40 MHz square wave, connected straight to scope with about 1 m RG58 cable.

Scope: Tektronix R7103
1. pic: Timebase 7B15, Vertical amp 7A29, BW 1 GHz
2. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-2, BW ?
3. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-4, BW ?
           This picture does not look good.
4. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-4, BW ?
          RG58 cable is connected with 20 dB attenuator to the scope

Edit:  Pic 4 added. Pic 3 removed.

[Wuerstchenhund]

I did a quick check of the Rigol DG1062z's square wave on a spectrum analyzer. There wasn't much time so I only tested 1MHz (where the square wave looks pretty ok) and 25MHz (where it's essentially shit). Cable is a new Huber & Suhner Sucoflex 100 which goes up to 18GHz. The BNC to N adapter is also Huber & Suhner, again rated to 18GHz.

The spectrum analyzer is an Agilent E7495B (actually it's a Base Station Test Set but pretty universal, I'll probably do a review at some point). The screenshots are a bit crap (light green on white background isn't nice) because I didn't check the capture settings where I guess the background can be changed to black as on the screen.

The two screenshots show nicely the various odd multiples of f₀ which make the 1MHz square wave while the 25MHz "square" wave only shows two peaks.

[Wuerstchenhund]

It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.

It shows just how much the measurement device itself can influence the result....RIS + sinX interpolation + 3d persistence.....really shows just how many artifacts can be attributed to the WAY in which a device interpolates what it's being fed.....I wanted to show just how far away we can get from something "trustworthy", especially when sampling and interpolating a signal..

I know, but I thought I should highlight the RIS issue anyways to avoid that someone takes the screenshot too literally.

Producing a model of a square wave, should be a very straight forward endeavor.....but everything in between that model and the way it's interpolated to the screen of a discreet device makes the whole concept quite a bit more "complicated".....in the "analog world" we live in....square waves just don't seem to want to exist.....and nature seems to like to avoid straight lines....

A perfect square wave can't exist, it's physically impossible as it assumes a indefinitely fast transition between low and high (which in this analog world is not possble). All we can get are more or less close approximations.

[TunerSandwich]

YIKES!!!

That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz.  My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you? 

My guess is running the built-in gen on the a-s at it's "limit" is producing useless data (in terms of analyzing the cabling and acquisition tool.

You have far nicer spectrum analyzer package than anything i have kicking around....

[Pjotr]

YIKES!!!

That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz.  My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you? 

There are many more issues here, like PCB layout and PSU pulse response/decoupling at the output drivers. Capacitors and inductors are as always, everywhere and ring as they like.

[Wuerstchenhund]

YIKES!!!

That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz.  My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....

Don't underestimate your scope  The WRXi-SPECTRUM option should turn your scope into a "real" spectrum analyzer, although a vector one and not an old-style swept one (which isn't necessarily a disadvantage), and of course with only 600MHz bandwidth.

you don't happen to have a ds2000A-S in house do you?

No, and what I've seen from Rigol so far nowadays I probably wouldn't touch another of their products with a bargepole. Admittedly some Rigol devices aren't as bad as say, Siglent, but after the DG1062z I've decided to stay with the big names.

You have far nicer spectrum analyzer package than anything i have kicking around....

You haven't seen my R&S CMU200 yet 

But seriously, the E7495A/Bs are great devices, where else can you get a portable Spectrum Analyzer (500kHz to 2.7GHz) that also comes with an RF generator (IIRC 200MHz to 2.7GHz), a power meter and a cable tester (1-port and 2-port measurements), all in a rugged and weatherproof case, for less than $1500?

It run Linux so there might even be a chance to extend the functionality by "hacking".

[TunerSandwich]

I know, but I thought I should highlight the RIS issue anyways to avoid that someone takes the screenshot too literally.

A perfect square wave can't exist, it's physically impossible as it assumes a indefinitely fast transition between low and high (which in this analog world is not possble). All we can get are more or less close approximations.

Yes, I had brought that up when one gentleman said the "1THz bandwidth" of the FFT function was impressive.....considering it can only be achieved with RIS and sin x/x I think it's a somewhat "useless" measure.

My main point in this whole discussion, is really regarding the original post.  In which it was sort of implied "use all of the horsepower you've got".  At least in my situation all that "horsepower" doesn't lead to anything of real value.  It's all interpolated and based on signal processing, and has very little bearing on the actual analog front end characteristics of the 64MXi.

I think that is a very important point to drive home....that the more bells and whistles and interpolations of the actual signal, the farther we get away from anything of merit or value.  In some ways the more impressive results are those showing as little interpolation and augmentation of the "true signal" as possible.  Which obviously can get VERY resource intensive ($$$$).  Cabling, true quality of source, post ADC "artifacts" etc....at some point I wonder just how useful a DSO is in regards to truly "characterizing" the "quality" of the sigGen. 

Seems like they are great for looking at the impulse responses (phase issues/ringing).....but for truly analyzing the "rise time" of the sigGen....hmmmm, seems like it's not so cut and dry....

[TunerSandwich]

YIKES!!!

That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz.  My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you? 

There are many more issues here, like PCB layout and PSU pulse response/decoupling at the output drivers. Capacitors and inductors are as always, everywhere and ring as they like.

absolutely.....I have to assume that is a given....I can't imagine any scope based FFT/specAn is going to have the clarity/fidelity of a dedicated device....which focuses it's investment resources on doing one thing "as good as it can"

[tautech]

My guess is running the built-in gen on the a-s at it's "limit" is producing useless data (in terms of analyzing the cabling and acquisition tool.

Yep. This is normally the case, dedicated FG's are superior.

Working on my main PC ATM, I'll post some waveforms later of what the inbuilt AWG can do in the SDS2304.
And as the have been a temp graded ones I'll do some of those too.

[TunerSandwich]

No, and what I've seen from Rigol so far nowadays I probably wouldn't touch another of their products with a bargepole. Admittedly some Rigol devices aren't as bad as say, Siglent, but after the DG1062z I've decided to stay with the big names.

As a "general purpose" "hobby" type scope the ds2000A is not too bad.  I actually really like it for some very specific things, but the math operations (especially FFT) is/are utterly useless.....I don't see any purpose in their "higher end" products though.....they just don't stack up, and you can get used examples of "big name" kit for roughly the same prices or less.....I imagine they don't sell many $5000 scopes or analyzers, and the company floats on the "hobby grade" stuff....

[Electro Fan]

Well, there is at least one turtle that benefits from a near perfect square wave source: Adjusting your high impedance HF probes as good as it gets

Ok, we have a nominee for a reason to care about a "strong" square wave 

[Electro Fan]

The picture is a 3D color persistence screen, which is essentially a more advanced variant of the common 2D persistence function many scopes have today.

Most scopes have a monochrome persistence function (i.e. intensity grading) where individual waveforms overlap each other on a single "depth" layer (the screen plane) and where the brightness represents the amount of times a waveform has passed through a particular spot on the screen. This can be used (in limits) to see jitter or other signal anomalies. More advanced scopes use color grading,

i.e. the color shows how often a waveform has passed through a particular spot, where red ('hot') shows places of high occurrence, yellow for medium occurrence and blue for low occurrence.

In a 3D persistence screen each waveform is 'stacked' on top of the other, which shows much better how the waveforms change over time. Again, the colors indicate the occurrence of a waveform passing through a certain spot in the horizontal (x/y) plane.

It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.

Thanks for the color legend and the overall explanation

[joeqsmith]

Hi,

I had a look at this picture:

The FFT shows spectral lines that are 5 GHz apart. This is sampling frequency of the scope 5G samples per second. The Lecroy scope is using RIS acquisition.

Regards,

Jay_Diddy_B

I agree.   

It is amazing how different the results are, between the two devices.....no doubt about that....I would argue that you have the superior scope for this kind of test.....?

I really was not interested in comparing the two setups for the 15MHz squarewave shape.    When I saw your original post with those spurs, it was not at all what I was expecting and I was thinking there was a software problem.   I checked my old LeCroy 7200 and did not see the spurs at the sample rate.    So I attempted to replicate it with my Wavemaster that has the latest version of X Stream loaded on it.   I tried various FFT settings to attempt to replicate those spurs and could not.   

I would have thought they would handle the FFT the same between the two DSOs but it appears they don't.    I assume you were using a boxcar.  What happens if you use a Hamming window?    Some other setting?   

Not useful but I thought it was strange. 

[TunerSandwich]

The RIS sample rate was 200GS, and the non RIS is 10GS (at that timebase), not 5GS......no boxcar on that.....just sin x/x and i believe the settings were power spectrum and flattop.....I can duplicate the result and show the setup screens.....

as you can see in the "broadband" plot the spurs extended out to around 100GHz and then began to roll off up to 200GHz....where there was a dramatic rolloff....pretty close to the way your scope behaved. 

It would be interesting to do a true quantitative comparison.....I will document the EXACT settings, and if you are inclined to spend the time, we could compare again. 

Maybe even load the same waveform into arb?  My signal source and cable were very much inferior to yours. 

The uniformity of the spurs is highly suspicious....in the "1THz" plot you can see the roll-off above 100GHz.....just to confirm you have a 5GHz front end on your WaveMaster?

[joeqsmith]

Yes, I would like to see if I could replicate your results it just because they seemed so strange.   

The data I showed was also sin x/x.  My DSO must also be in sin x/x to get 1THz with the FFT.   I also show the FFT in power spectrum and flat top.   

I don't think the 5G spurs has anything to do with the incoming signal but if you don't mind, try it and let me know.   I can always put it into the ARB if you find its a factor without any problem.   I just need a CSV or something file.   I can always translate it.   Just raw voltage is good enough.   

Yes, my 8500A has a 5GHz front end.   It's pretty old compared to yours but for my home use it is over kill.     

[TunerSandwich]

Yes, I would like to see if I could replicate your results it just because they seemed so strange.   

The data I showed was also sin x/x.  My DSO must also be in sin x/x to get 1THz with the FFT.   I also show the FFT in power spectrum and flat top.   

I don't think the 5G spurs has anything to do with the incoming signal but if you don't mind, try it and let me know.   I can always put it into the ARB if you find its a factor without any problem.   I just need a CSV or something file.   I can always translate it.   Just raw voltage is good enough.   

Yes, my 8500A has a 5GHz front end.   It's pretty old compared to yours but for my home use it is over kill.     

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster.  I will stay away from "wavestream" view (which I normally do anyhow, because it negates any sinx/x or ERES).  i didn't use ERES for the broadband plots....but did use it on the pulses focusing on the zoomed impulse responses....

I will see if I can load the proper signal into arb (PITA on the ds2000a-s).  if not I will try to get much more specific.  Also there is that cable issue (although I don't see how that should have anything to do with the spurs on my 600MHz front end). 

I will also try the same on CH3....and another option is to use the AP020 probe......do you have one?  That way we can have a more apples to apples comparison (again I doubt the cabling has anything to do with such a dramatic result). 

When I did the plot I didn't pay much attention to where the spurs were.....I just zoomed in to the region (roughly) where they had equivalent amplitude and assumed it was harmonic centers.....but now that it has been brought up, and I look closer, that doesn't seem right at all.....that is far too uniform across a bandwidth my front end doesn't even cover, to be signal....*scratches head*

[Jay_Diddy_B]

Hi group,

Here is a little simulation to show what happens with sampling and FFTs. This is to help explain the scope waveform.

I have constructed a model with a square wave with a 66ns period (15.1515 MHz) with a 1ns rise and fall times.

I have also modelled a 100MHz Bessel filter, this will soften the edges without introducing ringing.

And then I constructed a sample and hold to simulate sampling the waveform at 1 Gsps.

Here is the model:



This what the waveforms look like in the time domain:




And this is what the FFT results look like:




The top waveform shows the 1ns rise and fall time square waves. There are spectral lines at 15MHz, 45 MHz, 75 MHz .... There are only even harmonics because the square wave has a 50% duty cycle. There a dips at 1GHz 2GHz etc this comes from the 1ns rise and fall times.

In the second waveform the harmonics are attenuated by the response of the 100 MHz Bessel filter, so no real surprises here.

In the third waveform, we can see the effects of the sampling frequency. We have the baseband spectral lines, then we have components at sampling frequency +/- the baseband components, we also components at 2x sampling frequency +/- the baseband components etc.
This is a form of aliasing because in calculating the FFT we are looking at frequencies greater than half the sampling frequency (Nyquist Theorem) The FFT is only valid up to 500 MHz.



Regards,

Jay_Diddy_B

[joeqsmith]

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster.  I will stay away from "wavestream" view (which I normally do anyhow, because it negates any sinx/x or ERES).  i didn't use ERES for the broadband plots....but did use it on the pulses focusing on the zoomed impulse responses....

When I did the plot I didn't pay much attention to where the spurs were.....I just zoomed in to the region (roughly) where they had equivalent amplitude and assumed it was harmonic centers.....but now that it has been brought up, and I look closer, that doesn't seem right at all.....that is far too uniform across a bandwidth my front end doesn't even cover, to be signal....*scratches head*

For home, even my old 7200s have way more features than I use. 

My 8500A will do 20Gs/s interleaved, 200Gs/s RIS.    I would expect them to behave the same (for those 5G spurs).   Obviously, I was expecting to see 10G spurs.   I would not have thought to even look at it until you posted.    See, there was a point to this thread after all!   

I don't believe this is caused by the cable or input signal but give it a try.   Those spurs are so nice and flat on yours where mine has nothing. 

AP020 probe......do you have one? 

I only have resistive probes.    I plan to make some low freq buffers at some point to allow me it to work with 10X passive probes as well.   
Best to stick with coax. 

[Rupunzell]

Tektronix 7104, 2x 7A29, 7B10 & S50 pulser with SMA to BNC direct to the 7A29 input (50 ohm).
Base line is trigger channel.




Bernice

[Electro Fan]

Disclaimer:  even though I posted the original question I feel like I'm now posting really dumb commercials inside a seriously good TV program 

That said, I just tripped across the link below - it doesn't address all the end to end system issues (from the generator to the cabling to the scope) but it starts to get at the original question.  I think some of you might have read more into the original post than I intended - but that's A-OK, and I'm very happy to have stimulated the fuller discussion.

In my mind, a "strong" square wave is simply a square wave that looks very "square" - like what you try to get when adjusting a probe on a scope front panel.  And perhaps as many here have pointed out, there might not be a lot of other needs for a very square square wave. 

I don't know to what extent a computing or networking device needs a square square wave but I have to believe that although there are ways to pick out a 1 or a 0 from a relatively weak or poorly formed square wave at some point a very poorly formed square wave might confuse a receiving/decoding device.  No doubt my eyes seem to appreciate a highly square square wave more than most devices and circuits trying interpret square waves as 1s or 0s.  I guess that's a benefit of machines, they put up with workloads and conditions that people might not tolerate

So, again my post was about the simple observation of a square wave in a traditional or human perception/observational sense.  What drove the question was in part the fact that I've seen square waves that look more like sine waves to me from reputable equipment manufacturers who publish a spec for square waves - and at the upper end of the spec the square wave frankly looked kind of (very much) like a sine wave, at least to me.  So, I was just curious to see what people would call a square wave (at various frequencies and at various price points for generators).  Clearly I wasn't giving full consideration to the cabling and scope contributions - but it is great to see the discussion of the wider (and deeper) end to end considerations.

The article below addresses the question of "when is a square wave a square wave" - at least at an intermediate level.  I'll leave the advanced stuff to those here with more system-wide experience not to mention picosecond generators, GHz scopes - and color technologies. 

PS, I really enjoy this forum and I very much appreciate the fact that the pros and other senior members put up with entry level questions and comments.  There is huge amount of knowledge, experience, and good will in this forum and EEVblog overall.  You all rock in my book!  EF

http://mwrf.com/content/when-square-wave-truly-square
- this is a very good article; recommended; comments on it encouraged....

[Wuerstchenhund]

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster. 

The Wavemaster 8k does 20GSa/s interleaved or 10GSa/s on all channels. However the processing is much slower than on your WRXi even if the latter is equipped with the standard P-M Celeron 1.3GHz only. The WM8k (as the WP7k) came with a first gen P4 Celeron 1.7GHz with 256k cache/400MHz FSB (later scopes came with 2GHz Celeron) which was already a slow processor when these scopes were new, LeCroy was pretty much skimping on the processor power in their older X-Stream scopes (it got better in recent years). Unfortunately there's also a limit on what processor upgrades these scopes can take, although one could replace the mainboard for the one that is used in the WP7kA/WM8kA (later revision of the intel D865GLC) and which can take later revisions P4 processors with 3.2GHz/800MHz and faster. Just never enable Hyperthreading on a WP7k(A) or WM8k(A), ever!

[TunerSandwich]

Regardless of age, that is a superior scope....it obviously doesn't have the bells and whistles etc, but 5GHz front end is 5GHz front end....and I believe you can also do 10GS/s interleaved?   I have extended mem on mine plus all options, but I think you essentially have the same, or better "horsepower" in your wavemaster. 

The Wavemaster 8k does 20GSa/s interleaved or 10GSa/s on all channels. However the processing is much slower than on your WRXi even if the latter is equipped with the standard P-M Celeron 1.3GHz only. The WM8k (as the WP7k) came with a first gen P4 Celeron 1.7GHz with 256k cache/400MHz FSB (later scopes came with 2GHz Celeron) which was already a slow processor when these scopes were new, LeCroy was pretty much skimping on the processor power in their older X-Stream scopes (it got better in recent years). Unfortunately there's also a limit on what processor upgrades these scopes can take, although one could replace the mainboard for the one that is used in the WP7kA/WM8kA (later revision of the intel D865GLC) and which can take later revisions P4 processors with 3.2GHz/800MHz and faster. Just never enable Hyperthreading on a WP7k(A) or WM8k(A), ever!

Although I am VERY pleased with my WR64MXi....the 20GS/s is quite compelling, even by today's standards that is "high end".  Lots of data there....probably grabbing some stuff I am missing, especially at "longer" timebase...do the WM8k's have the "ERES" capability?  I have found that to be EXTREMELY useful for the type of stuff I use my MXi for, day to day.  I can only imagine that the HDO series is a pretty big step above pseudo +3 bits.....I have really been considering getting a demo loan on an HDO8k, but am too afraid I won't be able to send it back. 

[Wuerstchenhund]

Although I am VERY pleased with my WR64MXi....the 20GS/s is quite compelling, even by today's standards that is "high end".  Lots of data there....probably grabbing some stuff I am missing, especially at "longer" timebase...do the WM8k's have the "ERES" capability?

Sure, all 'true' LeCroy scopes¹at least since the early 90's when the 9300 Series came along had ERES, although if I remember right it was a software option back then.

I have found that to be EXTREMELY useful for the type of stuff I use my MXi for, day to day.  I can only imagine that the HDO series is a pretty big step above pseudo +3 bits.....I have really been considering getting a demo loan on an HDO8k, but am too afraid I won't be able to send it back.

The problem with ERES is that it limits the available bandwidth, i.e. my 3GHz WP7300A goes down to 160MHz in 11bit ERES mode. Naturally the HDOs don't suffer from that problem.

But if you can I'd wait a bit as it's very likely that we'll soon see true 12bit scopes at higher bandwidths and sample rates as the HDO Series offers from LeCroy. Especially after Keysight came out with the MSO-S.

Overall I'm extremely happy with my WP7300A which as an every-day scope has now completely replaced my WR64Xi and my LT264M (which I'll probably sell on as I can't see myself really needing to use them in the near future). 20GSa/s and 48M are helpful, and LeCroy's options are really outstanding (although these older scopes lack the SPECTRUM option, but stuff like serial decode for a dozen or so standards incl stuff like USB3 and Fibre Channel, and the Serial Data Analyzer option more than make up for that). I'll guess I'll hang-on to the WP7300A until the WP7zi gets into more sane price regions, and even then very likely keep it.

¹ Doesn't include the WaveAce and WaveJet Series

[EV]

I see Rigol DSO displays are being posted on this thread and comments about overshoot.

Here are pictures you asked:

Generator: Rigol DG4162, sync out, 40 MHz square wave, connected straight to scope with about 1 m RG58 cable.

Scope: Tektronix R7103
1. pic: Timebase 7B15, Vertical amp 7A29, BW 1 GHz
2. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-2, BW ?
3. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-4, BW ?

The last picture with S-4 sampling head does not look good. So I connected the RG58 cable with 20 dB attenautor to the S-4 sampling head and here are new pictures with 5 ns and 1 ns timebase.

[joeqsmith]

I tend to use a PC to control a lot of my equipment and then post post process the data with a modern PC.   

I had made a video showing some basic jitter measurements with Labview and had posted it in a LeCroy specific forum. Video can be seen here (WARNING it's pretty long and I am not real good at making videos):     


This spawned  a conversation with I assume a Teledyne sales guy about upgrading the DSOs MB.   The following is just a cut and paste to give some background: 

> Imaged the drive to back it up then started over. Pretty sure anyone playing with this sort of scope
> can handle installing an OS. ha ha

Not necessarily. Not saying this applies to you but I've lost count of the number of EEs I've met that know their field inside out but are complete numbties when it comes to computers.

................

> Yes, it has 256M. Task manager does not show a lot of swapping going on even with the 256. This
> MB supports up to 2G. I added a GB and reran my tests. No gains. You may be using a lot of the > DSOs math.

In fact I do. RAM helps quite a bit (especially since you can get DDR1 sticks for next to nothing these days), but the biggest improvement comes from a faster CPU with larger cache. X-Stream does all its calculations in the CPU cache which speeds up things, but the slow 512k processors LeCroy shipped with these scopes can be a bit of a bottleneck.

> For any post processing I would typically run Labview on a modern PC anyway.

If you have LabView then this is of course an option. But you can't do real-time stuff on LabView the same way you can do on the scope.

> I may install 1Gb Ethernet and see if I can pull the data out any faster.

I doubt that. The scope's mobo has a single 33MHz PCI32 bus which is also used by the aquisition adapter (which converts the 4x Gbit Ethernet links from the acquisition board to PCI). Aside from that the max 133MB/s (theoretical, in reality it's probably closer to around 90MB/s) overall bus bandwidth which is shared across all devices and from which the acquisition system already uses a bulk of, the timing in these scopes is pretty tight so introducing another card might have some side effects.

.....

>> If you have LabView then this is of course an option. But you can't do real-time stuff on LabView
>> the same way you can do on the scope.
>
> Not sure what you mean. Real-time?

LabView needs to gather the data from the scope first, which is awfully slow compared to the X-Stream software which has access to the acquisition data in real-time. If your scope has the XDEV option then you can get around that as it allows you to build your own applications that run on the scope directly.

> > I doubt that. The scope's mobo has a single 33MHz PCI32 bus which is also used by the
> > aquisition adapter (which converts the 4x Gbit Ethernet links from the acquisition board to PCI).
> > Aside from that the max 133MB/s (theoretical, in reality it's probably closer to around 90MB/s)
> > overall bus bandwidth which is shared across all devices and from which the acquisition system
> > already uses a bulk of, the timing in these scopes is pretty tight so introducing another card
> > might have some side effects.
>
> I plan to do some benchmarking on it. Tell me more about this timing problem. Maybe you can
> save me some time.

The acquisition interface acts as a PCI busmaster. The whole processes are very timing critical. The scope is designed so that the acquisition interface has the PCI bus for its own. Introducing a Gbit Ethernet interface which will cause noticable bus loading will probably result in side effects, i.e. lowered acquisition performance, abysmal slow network performance or the scope reacting funny.

I went ahead and ran the tests and made a few videos showing the outcome.

This first video shows the DSO running non-interlaced.   


After making the first video I noticed there was a big hit in download performance when running in interlaced mode.   I played with the DSO for a while then made this second video to show the results.



I had hoped the Teledyne people would jump in to clear up my misconceptions but after making the videos they stopped posting.   

[Wuerstchenhund]

I had hoped the Teledyne people would jump in to clear up my misconceptions but after making the videos they stopped posting.

The Yahoo LeCroy forum is sparsely visited, as the low post count over the years shows (I find myself checking it maybe once a month or less), and most discussions revolve around pre-X-Stream scopes (mostly 9300 and LC Series). Don't forget that even the oldest X-Stream scope (WaveMaster 8000) is still worth some noteworthy amount of money which makes it still prohibitively expensive for most hobbyists.

Don't get me wrong, the LeCroy Yahoo forum has been a great help in the past and this on several occasions, but it's not really the place for long-winded discussions like this thread, simply because there aren't enough people spending sufficient time in it.

[joeqsmith]

I had hoped the Teledyne people would jump in to clear up my misconceptions but after making the videos they stopped posting.

The Yahoo LeCroy forum is sparsely visited, as the low post count over the years shows (I find myself checking it maybe once a month or less), and most discussions revolve around pre-X-Stream scopes (mostly 9300 and LC Series).

Maybe the videos had nothing to do with sudden drop in responses.   If I were in sales and made a bold statement how I lost count of the number of EE's who are noobs when it comes to PCs and how making such a change was going to cause all sorts of problems, and then have a customer call me out,  I would not handle it by going silent.   

Honestly, I never did figure out what they were talking about.  I've had no problems with the 1Gb interface to date and never saw a down side to it.   

[TunerSandwich]

The problem with ERES is that it limits the available bandwidth, i.e. my 3GHz WP7300A goes down to 160MHz in 11bit ERES mode. Naturally the HDOs don't suffer from that problem.

Yes, but that is not a problem for the very specific things I use it for.  I.E. checking control signal in SMPS and other (various) low frequency DC-DC applications.  However, I would much rather see a true 12bit vertical reading, as I am not 100% sure on what levels of interpolation the ERES might be using....which obviously skews things to some degree or another. 

It has been an invaluable tool in catching over/under shoot, that normally would be missed.  I would love to see a true 12bit capture, along with a higher sample rate and some reasonable mem depth, for longer power quality captures.  That is probably my biggest complaint about the MXi I have.  It starts to lose a lot of performance and resolution/fidelity 2 long capture windows.  Obviously the PMA and other such utilities suffer because of that. 

If I expand the scope of my work (which is happening) the need for higher bandwidth, bit depth and sample-rate (plus mem) is there.  I did notice there were some trade-offs in the HDO series.  Would be nice to see LeCroy roll some technology into a single package.

I.E.
3GHz
12 bit
deep memory
industry leading sample rate
their excellent Ui/MAUI
bundle some spectral tools (with a dedicated FFT/spectrum button)
all packaged in nice form factor (which I think LeCroy does quite well) for a market leading cost
AND expand their current probe options.....
and update Wave studio (not a fan of it's interface, speed, etc...)

[Wuerstchenhund]

Maybe the videos had nothing to do with sudden drop in responses.   If I were in sales and made a bold statement how I lost count of the number of EE's who are noobs when it comes to PCs and how making such a change was going to cause all sorts of problems, and then have a customer call me out,  I would not handle it by going silent.   

Honestly, I never did figure out what they were talking about.  I've had no problems with the 1Gb interface to date and never saw a down side to it.   

Just because you were lucky doesn't mean that such mods are always troublefree. In fact, it might well be that your mod has other side effects you just didn't notice (yet). Just because something looks ok doesn't necessarily mean it is. Also, do you know how many different PCI 1Gbps network adapters exist? And just because you didn't see side effects with one makes you think it will always be allright? Hopefully not.

The simple fact is that these scopes are not designed as expandable systems, and just because you can plug in some PCI card doesn't mean it can be expanded like a standard PC. The scope as sold is the only supported (i.e. guranteed to work) configuration, aside from a few upgrades offered by LeCroy like CPU and RAM (which even if done with generic parts should be pretty painless). And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

In addition, the acquisition system in these LeCroy scopes definitely *is* timing sensitive. I've been bitten by this myself when I upgraded my CPU (hint: never enable Hyperthreading on a WP7k(A) or WM8k(A), unless you want to reinstall your OS).

This aside, "just works" isn't really good enough if you want to use your test kit professionally, where people generally want to have something that is supported by the manufacturer and where problems are solved by their support. If you modded your scope most manufacturers simply tell you to piss off, and rightfully so.

Maybe these EE's you were talking about weren't such 'noobs' at all.

I'm not going to ask why you need a 1Gbps network adapter in your scope. The standard intel 100Mbps Ethernet port should be more than enough for transferring data or remote controlling it.

BTW, the Yahoo LeCroy forum is operated by a guy who has nothing to do with LeCroy other than using their scopes (and helping members). In fact, there are only two LeCroy affiliated member I know of, and they certainly don't use the forum as a marketing vehicle. But generally you can expect that the familiars there pretty well know know what they're talking about.

[Wuerstchenhund]

Yes, but that is not a problem for the very specific things I use it for.  I.E. checking control signal in SMPS and other (various) low frequency DC-DC applications.  However, I would much rather see a true 12bit vertical reading, as I am not 100% sure on what levels of interpolation the ERES might be using....which obviously skews things to some degree or another. 

There's no interpolation in ERES. You are getting the full 11bit resolution, at the cost of bandwidth. Here's a LeCroy document explaining ERES in more detail (it's from 1999 but still remains valid):
http://teledynelecroy.com/doc/digital-oscilloscopes-enhanced-resolution

It has been an invaluable tool in catching over/under shoot, that normally would be missed.  I would love to see a true 12bit capture, along with a higher sample rate and some reasonable mem depth, for longer power quality captures.  That is probably my biggest complaint about the MXi I have.  It starts to lose a lot of performance and resolution/fidelity 2 long capture windows.  Obviously the PMA and other such utilities suffer because of that. 

I know that they're working on expanding their High Definition 12bit technology into higher end scopes, I guess eventually all their mid-range and high-end scopes will be 12bit, aside from the LabMaster maybe (which is a different beast anyways). The HDOs are nice but they're essentially WaveSurfers on steroids only. There's also of course the WaveRunner HRO but again 2GSa/s only, and very likely one of the next models to go.

If I expand the scope of my work (which is happening) the need for higher bandwidth, bit depth and sample-rate (plus mem) is there.  I did notice there were some trade-offs in the HDO series.  Would be nice to see LeCroy roll some technology into a single package.

I.E.
3GHz
12 bit
deep memory
industry leading sample rate
their excellent Ui/MAUI
bundle some spectral tools (with a dedicated FFT/spectrum button)

The button already exist on the WaveRunner 6zi/HDO. But I think that the SPECTRUM option should be standard for WaveRunner and higher models, really.

all packaged in nice form factor (which I think LeCroy does quite well) for a market leading cost

Indeed, LeCroy does the packaging quite well, and often does have some things (i.e. an adjustable widescreen display with pivot mode on the WR6zi/HDO, or the detachable control panel and the dual BNC/SMA inputs on the WP7zi) you just can't find anywhere else.

Cost-wise I don't think they have a problem. LeCroy has been cheaper than Agilent/Keysight and Tek pretty much forever when comparing comparable scopes, and unlike Tek they are very flexible in their pricing.

AND expand their current probe options.....

What do you miss?

and update Wave studio (not a fan of it's interface, speed, etc...)

Well, it's ok for a free program, and while it's slow it still much better than the equivalents from Keysight and Tek. The update rate is difficult to increase as the program captures individual screenshots and not a video stream. If you want faster then just login via RDP. Works like a charm even on XP, and even better on Windows 7 scopes.

[TunerSandwich]

What I would like to see them do, is sort of a "best of" from all of their current lines....

screen and interface options from the units you mentioned....12 bit, big mem, high sample rate....keep it in line with the general LeCroy "value model".

would like to see a current probe with more sensitivity and bandwidth at higher current (don't mind paying for that).....or at least update the AP015 to take just a bit more current for that 10 second window and give me 100MHz (and update the deskew process, to be a bit less "clunky").  They just seem to take a big jump from the CP031 to the CP150, with nothing really in between...

on the wave studio front...I would like to see them take a more direct approach, as opposed to screen capture (the current trace tools aren't at all good IMO)....maybe just use a template that looks like the scope Ui and stream data into the waveform and measurement sections (might not be possible, from a processing perspective).....also give us the ability to create new Ui building blocks in WS would be nice.  Think of it as just a "customizable skin/bounding boxes" approach, with some blocks that contain a live update on statistics/waveforms.....and the ability to include markers/tags....that would be very useful for reporting.....also a direct "video capture" would be nice and maybe throw in some simple "one click" encoding and uploading buttons, for example a quick HD capture/encode/upload to a vimeo pro account, for sharing etc....obviously all of that can be done to some extent now, with discreet software packages and a lot of hassle....but a "one click" approach would be nice.....

maybe I am expecting/asking too much....

i would like to see all of those features, plus what we already discussed....in an 8 channel scope (modular front end would be awesome....like labmaster....especially external clock gen/sync)....for somewhere under $40k (with some options) maybe under $45k.  In this day and age charging what they charge for PMA and spectrum, seems a bit out of line with others....

It would be very cool if someone came up with a more modular way of displaying data....tab view, and the ability to move statistics and waveform windows independently to various screens......AND allow users who have external touch screen monitors to retain the touch capability when splitting out to ext monitor.....and give me 2 ext monitor outs...

[joeqsmith]

Just because you were lucky doesn't mean that such mods are always troublefree. In fact, it might well be that your mod has other side effects you just didn't notice (yet). Just because something looks ok doesn't necessarily mean it is. Also, do you know how many different PCI 1Gbps network adapters exist? And just because you didn't see side effects with one makes you think it will always be allright? Hopefully not.

Data is data.  Better than dealing with how someone feels it's going to work.  I provided info on the board I am currently using.  Also tested with a bottom end Star tech card.  Saw no problems with it. 

The simple fact is that these scopes are not designed as expandable systems, and just because you can plug in some PCI card doesn't mean it can be expanded like a standard PC. The scope as sold is the only supported (i.e. guranteed to work) configuration, aside from a few upgrades offered by LeCroy like CPU and RAM (which even if done with generic parts should be pretty painless). And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

In addition, the acquisition system in these LeCroy scopes definitely *is* timing sensitive. I've been bitten by this myself when I upgraded my CPU (hint: never enable Hyperthreading on a WP7k(A) or WM8k(A), unless you want to reinstall your OS).

This aside, "just works" isn't really good enough if you want to use your test kit professionally, where people generally want to have something that is supported by the manufacturer and where problems are solved by their support. If you modded your scope most manufacturers simply tell you to piss off, and rightfully so.

Maybe these EE's you were talking about weren't such 'noobs' at all.

I'm not going to ask why you need a 1Gbps network adapter in your scope. The standard intel 100Mbps Ethernet port should be more than enough for transferring data or remote controlling it.

Certainly if I worked for Teledyne, I would see making a general statement about EE's in this manner in a public forum as pissing my job down the toilet. 


I data I presented in the video shows a point to point running 400Mb, no problem.   Not sure why your thinking 100Mb on a Gig connection. 

Looking at this particular DSO's dead time:

10GS/s, collecting 5Ms requires 640ms.   If the PCI bus could handle 60MB sustained, it would require 83ms to move the data or about 13% of the bus BW.   Say the Ethernet can move the data at 50Mb/s which is about what I was getting with the built in board.   So about 6.25MB/second.   Moving 5Ms will require about 800ms.     

If we want to handle the data and not miss any of the little data the DSO does happen to collect, the 100Mb won't cut it.     At 400Mb/s with the 1G Ethernet, this time drops to 100mS.  Maybe enough time to move the data to the modern PC, post process and display it.   

At 10GS/s and collecting 200Ks requires 35ms.   Staying with 60MB on the PCI bus, it would require 3.33ms or about 9.5% of the bus.  The Ethernet transfer would be about 32ms using 100Gb. 

The one video I posted showed some of the longer collections.  Dead times were several seconds.   It's not a bad DSO but you can miss a lot of information with it.   It's a pretty common complaint.   I have no idea if their new products are better.  Where I work we switched to Agilent. 

I suspect there are other bottlenecks in this system causing the poor dead times beyond the PCI bus.   May put a probe on it at some point to see what is going on.   

I can't see calling Teledyne and ask for support on a 14 year old  system.   I bought this one for home use, not for anything "professional"  but I appreciate your concerns.     

BTW, the Yahoo LeCroy forum is operated by a guy who has nothing to do with LeCroy other than using their scopes (and helping members). In fact, there are only two LeCroy affiliated member I know of, and they certainly don't use the forum as a marketing vehicle. But generally you can expect that the familiars there pretty well know know what they're talking about.

After posting about the VNA in that forum, I had Teledyne sales contact me using my work email wanting to know who he could contact.    Don't kid yourself.  They use it for marketing.  No big deal.  I would expect them to. 

[TunerSandwich]

I data I presented in the video shows a point to point running 400Mb, no problem.   Not sure why your thinking 100Mb on a Gig connection. 

That is not possible.  There is an error in the data/math there.  1Gb = 125MB, with NO protocol overhead....ethernet protocols are going to slash at least some margin off that....if you see 90-100MB full duplex you are lucky, and have a top NiC/cabling etc etc etc....

I have some fancy NAS/SAN devices here at work, running LACP (802.3ad) link aggregations, and top tier controllers, drives, cabling etc....and we are lucky to see a sustained 130-150 MB rate, on large blocks....forget small blocks of non contiguous file headers....that has generally mirrored my experiences in that realm for the last couple decades....

are you confusing MB and Mb?  As you can see below Wuer is talking MB and above you are talking Mb....big difference there

Just to clarify are you saying 400Mb on 1Gb ethernet?  If that is the case, sure....0.4Gb....but Wuer said 100MB, which is generally accurate on 1Gb ethernet, provided everything is going well and you have large contiguous blocks, with no dropped packets....

And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

[Rupunzell]

Could this measurement be run without the RG58 coax, connectors and related adapters? Use only a single adapter if possible between the S4 head and generator output as there appears to be a reflection from the RG58 coax/connectors/adapters.

See circled areas in this altered image:



Bernice

Here are pictures you asked:

Generator: Rigol DG4162, sync out, 40 MHz square wave, connected straight to scope with about 1 m RG58 cable.

Scope: Tektronix R7103
1. pic: Timebase 7B15, Vertical amp 7A29, BW 1 GHz
2. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-2, BW ?
3. pic: Timebase 7T11, Vertical amp 7S11 with sampling head S-4, BW ?

The last picture with S-4 sampling head does not look good. So I connected the RG58 cable with 20 dB attenautor to the S-4 sampling head and here are new pictures with 5 ns and 1 ns timebase.
[/quote]

[TunerSandwich]

I data I presented in the video shows a point to point running 400Mb, no problem.   Not sure why your thinking 100Mb on a Gig connection. 

That is not possible.  There is an error in the data/math there.  1Gb = 125MB, with NO protocol overhead....ethernet protocols are going to slash at least some margin off that....if you see 90-100MB full duplex you are lucky, and have a top NiC/cabling etc etc etc....

I have some fancy NAS/SAN devices here at work, running LACP (802.3ad) link aggregations, and top tier controllers, drives, cabling etc....and we are lucky to see a sustained 130-150 MB rate, on large blocks....forget small blocks of non contiguous file headers....that has generally mirrored my experiences in that realm for the last couple decades....

are you confusing MB and Mb?

1000Mbit connection or yes 125MByte.  Getting 400Mbit or 50Mbyte data rates.   Project I am working on will run at 500Mbit sustained until I fill a TB drive and not miss a beat.   No problem.     In the case of the DSO, I tried a direct link then ran it through the old crappy Cisco.  No performance hit.     Keep in mind that the overall average data rate for the DSO will be much much lower.  This is a burst.  Then we wait for the DSO to collect it thoughts.
 

Ok, that is fine...but Wuer said 100MB and you retyped it as 100Mb and said you didn't understand why he said that was impossible.....he didn't say 100Mb.....you misread or misquoted that....50MB on 1Gb ethernet is no problem....even on small blocks you should get somewhere around 47MB, so 50MB is totally in the realm....but 400MB on 1Gb, no way.....

I see a misquote on your end....that's why it's not adding up.  Wuer is bang on with his statement of 100MB on 1Gb ethernet....and he is being generous there. 

When you showed your data on the LeCroy forum, did you mistakenly flip those MB vs Mb figures?  If so I can see why no one responded....not trying to be rude at all, just trying to point out that those bits of terminology are pretty damn critical in making any realistic assessments

Another issue there is "burst" rates typically apply to contiguous streams of data....small files, with small byte/sector allocations on drives are going to put those theoretical rates in the dumpster....

Big files, going between magnetic drives, with 4k byte sectors....over ethernet MIGHT get 100-110(ish) MB/sec....SSD is no help there either as the reduced (non existent really) seek times aren't very relevant.....ethernet is still dealing with packets snd, rec, ack etc....there is much more latency there than the drives....

How is the LeCroy provisioning this data?  I don't mean internally, I mean off through the PCi bus, into the NiC and on down the line....there is going to be far more complexity, overhead etc, over ethernet than any potential latencies across PCi bus or associated mem controllers etc.....

Even the most arcane SATA drive is going to get limited by the network overhead.....If I recall correctly, most OTS/modern magnetic drives have a seek time of around 3-20ms. 

Maybe we are talking apples an oranges here and I need to go back and read what you posted prior, but in terms of Wuer being wrong about 1Gb ethernet being capped @ 100MB/s, he isn't.....that is how it goes.  Again he didn't say 100Mb/s as you re-wrote it....key key point there....

[joeqsmith]

are you confusing MB and Mb?  As you can see below Wuer is talking MB and above you are talking Mb....big difference there

 

Quote from: Wuerstchenhund on Today at 06:04:46 AM

And really, it should be pretty obvious to an EE why on a single PCI bus with a theoretical max transfer rate of 133MB/s a 1Gbps network adapter (which in a good environment transfers between 90-100MB/s) doesn't leave much room for anything else. And something like 33MB/s isn't much for an acquisition system which captures over 20GB data per second, and while not everything in the sample memory goes to the CPU, everything that you want to see on the screen or that you want to process in any way does. Well, you do the math.

Right a 1Gbps adapter in a good environment transfers between 90-100MB/s.   Again, I am getting around 400Mb or 50MB.  Around 50%.   I must  be missing the question.

[joeqsmith]

Ok, that is fine...but Wuer said 100MB and you retyped it as 100Mb and said you didn't understand why he said that was impossible.....he didn't say 100Mb.....you misread or misquoted that....50MB on 1Gb ethernet is no problem....even on small blocks you should get somewhere around 47MB, so 50MB is totally in the realm....but 400MB on 1Gb, no way.....

I see a misquote on your end....that's why it's not adding up.  Wuer is bang on with his statement of 100MB on 1Gb ethernet....and he is being generous there. 

When you showed your data on the LeCroy forum, did you mistakenly flip those MB vs Mb figures?  If so I can see why no one responded....not trying to be rude at all, just trying to point out that those bits of terminology are pretty damn critical in making any realistic assessments

  missed that.    Makes more sense now that I reread it.  I was thinking man, 100Mb on a 1Gb connection is good?     
No problem.  Good catch.    My original post to the LeCroy forum:

A short video showing the results of adding a 1000Gb board to the Wavemaster.  I used an Intel PRO/1000 GT Ethernet board which supports off loading some of the processing that the OS would normally have to do. 

I can leave both ports attached to the switch, each with their own IP and select the card I want to use from Labview.   XStream has no problems with it.   

I ran some tests with larger MTU size, Nagle enabled, changing the DSOs software priority and direct connection to the PC rather than using the Cisco switch.   Gains were minimal.

The one thing that I do notice that is not in the video, at 20GS/s the poor DSO has no time left to service the Ethernet.   Depending on what you are doing, I have seen average data rates as poor as 10Mb-20Mb with the 100Mb port.    In all cases the add-on board yielded better performance.   

[TunerSandwich]

Ok, that is fine...but Wuer said 100MB and you retyped it as 100Mb and said you didn't understand why he said that was impossible.....he didn't say 100Mb.....you misread or misquoted that....50MB on 1Gb ethernet is no problem....even on small blocks you should get somewhere around 47MB, so 50MB is totally in the realm....but 400MB on 1Gb, no way.....

I see a misquote on your end....that's why it's not adding up.  Wuer is bang on with his statement of 100MB on 1Gb ethernet....and he is being generous there. 

When you showed your data on the LeCroy forum, did you mistakenly flip those MB vs Mb figures?  If so I can see why no one responded....not trying to be rude at all, just trying to point out that those bits of terminology are pretty damn critical in making any realistic assessments

  missed that.    Makes more sense now that I reread it.  I was thinking man, 100Mb on a 1Gb connection is good?     
No problem.  Good catch.    My original post to the LeCroy forum:

A short video showing the results of adding a 1000Gb board to the Wavemaster.  I used an Intel PRO/1000 GT Ethernet board which supports off loading some of the processing that the OS would normally have to do. 

I can leave both ports attached to the switch, each with their own IP and select the card I want to use from Labview.   XStream has no problems with it.   

I ran some tests with larger MTU size, Nagle enabled, changing the DSOs software priority and direct connection to the PC rather than using the Cisco switch.   Gains were minimal.

The one thing that I do notice that is not in the video, at 20GS/s the poor DSO has no time left to service the Ethernet.   Depending on what you are doing, I have seen average data rates as poor as 10Mb-20Mb with the 100Mb port.    In all cases the add-on board yielded better performance.   

If you don't use LACP to aggregate the ports on the NiC, then running each on it's own IP actually increases processing overhead.  You basically have an idle port, trying to look for data.  If you want to divide packets across the aggregate then LACP needs to be in place throughout the chain...both source and destination, and ANY device (switch etc) in-between needs to have those links operating as a "team".  If you team those ports, you don't exactly have a 2Gb/s port either, as there is overhead in the LACP. 

Intel PRO NiC is top tier kit....a lot of older Cisco switches don't support (802.3ad) dynamic links.....also running into a switch is not a point to point connection.....the switch re-prioritizes packets, depending on lots of things.....you can, however tag packets with priority...using QOS. 

I know that is all a bit off topic here, but just adding a bit of insight on how that all comes together in the real world.  I had a brief stint as a Cisco tech (CCNA cert) and thought some of that jargon might shed some light on some faults in methodology. 

Larger MTU doesn't necessarily benefit things.....a lot of devices don't handle jumbo frames in the same way.  Generally MTU of 9000 or more doesn't necessarily yield the result you might expect.....for example intel PRO NiC might call a jumbo frame 9000 MTU and a Cisco switch might call it 9090...etc etc etc....it's an endless clusterfuck of manufacturers not being on the same page....and a very loose classification about what a "jumbo frame" really is.....as a general rule stay away from jumbo frames....they very often don't help anything, and very often hurt things.....unless you have really sussed out the need, and entire chine of events that are handling that packet (and assuming that the source is even packaging that at the MTU).

[joeqsmith]

If you want to divide packets across the aggregate then LACP needs to be in place throughout the chain...both source and destination, and ANY device (switch etc) in-between needs to have those links operating as a "team".  If you team those ports, you don't exactly have a 2Gb/s port either, as there is overhead in the LACP. 

I can leave both ports attached to the switch, each with their own IP and select the card I want to use from Labview.   

I saw no difference in performance leaving them connected to the switch.   No attempt was made to team the ports.   The one on the DSO is again a 100Mb.  So yea, 2Gb/s with them combined is not going to happen.  Forget the overhead.

also running into a switch is not a point to point connection.....the switch re-prioritizes packets, depending on lots of things.....you can, however tag packets with priority...using QOS. 

I never stated that running through a switch was point to point.  Read it again eagle eyes.   

I ran some tests with larger MTU size, Nagle enabled, changing the DSOs software priority and direct connection to the PC rather than using the Cisco switch.   Gains were minimal.

Just tried a few quick tests, left it with the defaults and called it a day.   No big deal or effort. 

[TunerSandwich]

I never stated that running through a switch was point to point.  Read it again eagle eyes.   

Eagle eyes?  no need to be rude you know, this isn't a pissing contest.....I was trying to help you understand your flawed methodology.  If you want to play it like that though....best of luck, just don't be surprised with the responses you are getting.....if you are getting MB and Mb confused, and then telling people they are wrong, you aren't going to have much luck....

sheesh was just trying to help you.....I guess no good deed goes unpunished.   

Either way, still love ya buddy and best of luck <3

[joeqsmith]

I know that is all a bit off topic here, but just adding a bit of insight on how that all comes together in the real world.  I had a brief stint as a Cisco tech (CCNA cert) and thought some of that jargon might shed some light on some faults in methodology. 

Off topic??  Really?         This thread is a free for all.   

Really, if someone were to go out and buy a brand new DSO to look at their square waves, I think this is all good info to consider!  Press on....

[joeqsmith]

I never stated that running through a switch was point to point.  Read it again eagle eyes.   

Eagle eyes?  no need to be rude you know, this isn't a pissing contest.....I was trying to help you understand your flawed methodology.  If you want to play it like that though....best of luck, just don't be surprised with the responses you are getting.....if you are getting MB and Mb confused, and then telling people they are wrong, you aren't going to have much luck....

sheesh was just trying to help you.....I guess no good deed goes unpunished.   

Either way, still love ya buddy and best of luck <3

Pissing contest??       I was not trying to be rude.  Just pointing out that you too make mistakes when you are reading.  We all do.  Rolls off me no problem.  I screw up all the time.   

[Wuerstchenhund]

TunerSandwich beat me to it so I don't think it's necessary to reiterate where your misunderstanding is. Just let me address this:

Agilent taking on a LeCroy...
 
Article that explains dead times and compares a few scopes...
http://cp.literature.agilent.com/litweb/pdf/5989-7885EN.pdf

Agilent marketing material as source? Seriously? From a company that has a widely known history of twisting reality up to borderline lying?

I haven't looked at the video but the pdf file is typical Agilent. Based on the listed waveform rates it seems the unspecified WaveSurfer is a WaveSurfer 400 (the first compact LeCroy Windows lower mid-range scope, which ran XP but overall was a very basic scope), which has been out of production for roughly a decade. The WaveRunner waveform data very much looks like a WaveRunner2 LT, which is a VxWorks based scope introduced in 2001 which was stopped being sold roughly 11 years ago. And the WaveJet looks like a WaveJet 300 (non-A) which is a similarly old model. This Agilent paper is dated 2014, but it seems for them to get their point across LeCroy had to compare their current scopes with 10+ year old competitor models. Not that this is surprising, considering their history of being sparse with the full truth.

They also seem to ignore is that most LeCroy scopes reach their max waveform rates in segmented mode. Your WM8k, if I remember right (I don't have the data at hand for that model), is spec'd with around 100k wfms/s. My WP7300A is spec'd with up to 150k wfms (which it does achieve), and TunerSandwich's and my WR64Xi is spec'd with 1.25M wfms/s (which it does achieve as well). Scopes starting with the WRXi also have a mode called "WaveStream" which lets the scope run at much higher update rates than in normal mode. So even though these scopes are pretty old by today's standards they still can achieve high waveform rates, if operated correctly. Of course none of that is mentioned by Agilent.

I guess this is why Agilent obviously had to resort to older models for their "comparison" to "take on LeCroy", because LeCroy's current scopes had look their scopes like toys (at least in the mid-range and high-end, LeCroy's entry level line is still crap). So I guess the bottom line is that their 2014 scopes do pretty well against 10+ year old scopes from their competitors.

Well done Agilent 

[TunerSandwich]

TunerSandwich beat me to it so I don't think it's necessary to reiterate where your misunderstanding is. Just let me address this:

Agilent taking on a LeCroy...
 
Article that explains dead times and compares a few scopes...
http://cp.literature.agilent.com/litweb/pdf/5989-7885EN.pdf

Agilent marketing material as source? Seriously? From a company that has a widely known history of twisting reality up to borderline lying?

I haven't looked at the video but the pdf file is typical Agilent. Based on the listed waveform rates it seems the unspecified WaveSurfer is a WaveSurfer 400 (the first compact LeCroy Windows lower mid-range scope, which ran XP but overall was a very basic scope), which has been out of production for roughly a decade. The WaveRunner waveform data very much looks like a WaveRunner2 LT, which is a VxWorks based scope introduced in 2001 which was stopped being sold roughly 11 years ago. And the WaveJet looks like a WaveJet 300 (non-A) which is a similarly old model. This Agilent paper is dated 2014, but it seems for them to get their point across LeCroy had to compare their current scopes with 10+ year old competitor models. Not that this is surprising, considering their history of being sparse with the full truth.

They also seem to ignore is that most LeCroy scopes reach their max waveform rates in segmented mode. Your WM8k, if I remember right (I don't have the data at hand for that model), is spec'd with around 100k wfms/s. My WP7300A is spec'd with up to 150k wfms (which it does achieve), and TunerSandwich's and my WR64Xi is spec'd with 1.25M wfms/s (which it does achieve as well). Scopes starting with the WRXi also have a mode called "WaveStream" which lets the scope run at much higher update rates than in normal mode. So even though these scopes are pretty old by today's standards they still can achieve high waveform rates, if operated correctly. Of course none of that is mentioned by Agilent.

I guess this is why Agilent obviously had to resort to older models for their "comparison" to "take on LeCroy", because LeCroy's current scopes had look their scopes like toys (at least in the mid-range and high-end, LeCroy's entry level line is still crap). So I guess the bottom line is that their 2014 scopes do pretty well against 10+ year old scopes from their competitors.

Well done Agilent 

I also found myself laughing at the Agilent sample rates being touted as "industry leading" "groundbreaking" "unheard of price to performance" etc etc etc etc.....and by that token, found myself rolling on the ground howling when Tek markets the MDO by the same merits.....

It seems like even juan huong lo can offer specs like those.....for pennies on the "big guys" dollars.....and forget it when even comparing to something LeCroy moved on from over 10 years ago....

One thing I will give Agilent over LeCroy though....they don't dick around when it comes to processing performance.....they make easily the most responsive scopes I have ever put my hands on....LeCroy might have gotten better at this, as the computing power in their devices has gone up, but it's still offloaded to a general purpose microprocessor and OS.....and obviously Tek is off in some bubble of another universe when they think their products are competitive (in that regard)

Agilent seems to have a nice way of packaging their equipment into very very nice Ui's....fast to respond, truly excellent layouts....logical hierarchies etc etc....but then when it comes down to the "real" specs....it the same old repackaged chips, from 2 generations ago....which admitedly LeCroy is doing as well....however their chips from "2 generations ago" still seem to offer "more"....

It's very difficult to wade through the bullshit in new scopes and other t&m gear.....makes you just want to buy something that is already "obsolete" but still does exactly what you NEED, and have a good chuckle over the marketing BS some of these companies use to keep the consumer engine running.....

[TunerSandwich]

I haven't looked at the video

I just watched it, and that is the most feeble basis for comparison I have ever seen....he basically says that "although you can do the same things on the lecroy, you have to know what you are doing.....on the agilent you just draw a box" (this is regarding triggering).....so the marketing here is buy Agilent, because you don't need to know anything about how things work to use it....are you serious?  If you can't set-up a basic trigger function, then you have no idea about what you are measuring, how it works, how to solve a potential problem (even if your scope can find it) etc etc etc....

If I may be so bold to revise this marketing video....and sum it up in one catchy phrase, which will most certainly sell it....."Agilent : scopes for those with no time to think

To be fair I have seen some of this same bullshit comparison marketing from LeCroy as well....albeit slightly less ridiculous....why can't these companies just show what they sell, what it does, how much it costs, and what the terms are....I already know what i need, without them telling me who else is doing what.....and then assuming I believe one word of it.  Save the money, discount the scope, give me a compelling incentive on that basis (value) and move on.... I already like your products Agilent and don't need a fluffer

[Wuerstchenhund]

I also found myself laughing at the Agilent sample rates being touted as "industry leading" "groundbreaking" "unheard of price to performance" etc etc etc etc.....and by that token, found myself rolling on the ground howling when Tek markets the MDO by the same merits.....

Indeed. I guess the only "industry leading" thing from them is the amount of BS in their marketing stuff.

One thing I will give Agilent over LeCroy though....they don't dick around when it comes to processing performance.....they make easily the most responsive scopes I have ever put my hands on....LeCroy might have gotten better at this, as the computing power in their devices has gone up, but it's still offloaded to a general purpose microprocessor and OS.....and obviously Tek is off in some bubble of another universe when they think their products are competitive (in that regard)

Agilent seems to have a nice way of packaging their equipment into very very nice Ui's....fast to respond, truly excellent layouts....logical hierarchies etc etc....but then when it comes down to the "real" specs....it the same old repackaged chips, from 2 generations ago....which admitedly LeCroy is doing as well....however their chips from "2 generations ago" still seem to offer "more"....

I have to disagree here a little bit. It's true that Agilents scopes are very responsive, but the same is true for newer LeCroy scopes as well. A DSOX2k/3k is a very responsive scope (don't forget that these are relatively simple scopes using some closed down version of Windows CE), but the same is true for the WaveSurfer 3000 (LeCroy's equivalent of the DSOX3k(T) which is also a closed down Windows Embedded based scope) which is similarly responsive. Newer LeCroy's scopes (X-Stream II using PCIe) that run a full version of Windows are as much responsive as their Agilent/Keysight counterparts.

No argument about Tek who seems to be stuck in the past.

Older LeCroy Windows scopes (X-Stream I scopes which are based on 32bit PCI) like your WRXi could often feel a bit laggy as they were pretty much underpowered, simply because LeCroy cut some corners on CPUs (slow Celerons with small caches, resulting in the CPU getting maxed out regularly) and RAM (which is a bit ridiculous, considering the low prices of better CPUs and the high price tags of these scopes). But these problems can be overcome by simple upgrades. On my WR64Xi, general responsiveness improved noticably after I upgraded from the slow Celeron 1.3Ghz/512k to a Pentium-M 1.8GHz/2MB, the RAM to 1GB (max for that scope) and the painfully slow 4200rpm IDE drive to a modern SATA 5400rpm hard drive (installing updated drivers for chipset, gfx etc helped, too). On my WavePro 7300A (which already came with the LeCroy upgraded processor, a P4 2.53GHz with 512k cache and 533MHz FSB, as well as 2GB RAM), changing the processor to a P4 3.2GHz (1MB cache, 800MHz FSB), upgrading the RAM to 3GB and replacing the old IDE hard drive with a fast intel SATA SSD320, the scope went from laggy to instantaneous reaction to inputs. It's now easily as responsive as the Agilent DSO9k and 90k scopes I use at work.

As to Agilent's UI, I agree for their entry level scopes (i.e. DSOX2k/3k) which do have a nice UI, but as to their desktop Windows based scopes I think the UI isn't great. Yes, they have touch, but it still is pretty obvious that the whole thing was originally designed with mouse control in mind, not with touch, and that it's all based on the mouse UI of the old Infiniium 54800 Series running Windows95 (which wasn't exactly a stellar example of great UI design). Recent scopes gave the UI a bit of an overhaul, but the main flaws remain.

Agilent scopes do have a pretty simple front panel layout, though, and usually come with individual vertical controls for each channel. Aside from the WR6k(A), WP7k(A) and WM8k(A) LeCroy still has a single vertical control for all channels, and while the general layout of most LeCroy scopes is pretty similar across all products (aside WaveAce/WaveJet and WS3k), things like the SUperKnob on the WR6zi/HDO can be confusing to users unfamiliar with that scope.

How important individual vertical controls are is certainly a thing of individual preference. I enjoy the individual knobs on my WP7kA, but the single control on other LeCroy scopes never bothered me (but then I also liked the single knob front panel of the early HP 54500 Series).

It's very difficult to wade through the bullshit in new scopes and other t&m gear.....makes you just want to buy something that is already "obsolete" but still does exactly what you NEED, and have a good chuckle over the marketing BS some of these companies use to keep the consumer engine running.....

Agreed. Not that this is a bad option, though, as buying older gear (especially if it's still supported) can actually save you a lot of money, and in some cases (i.e. Rigol and Siglent scopes) leave the beta testing to someone else.

[EV]

Could this measurement be run without the RG58 coax, connectors and related adapters? Use only a single adapter if possible between the S4 head and generator output as there appears to be a reflection from the RG58 coax/connectors/adapters.

See circled areas in this altered image:



Bernice

Yes it is possible to connect Tek 284 directly to S-4 sampling head with 20 dB attenuator but not easy. It is difficult without a big table and I don't have it now.  These reflections do not bother me. There are same reflections in pictures 1 and 2 which are taken without attenuator between the RG58 cable and scope. Look at my reply #249.

[Wuerstchenhund]

I just watched it, and that is the most feeble basis for comparison I have ever seen....he basically says that "although you can do the same things on the lecroy, you have to know what you are doing.....on the agilent you just draw a box" (this is regarding triggering).....so the marketing here is buy Agilent, because you don't need to know anything about how things work to use it....are you serious?  If you can't set-up a basic trigger function, then you have no idea about what you are measuring, how it works, how to solve a potential problem (even if your scope can find it) etc etc etc....

If I may be so bold to revise this marketing video....and sum it up in one catchy phrase, which will most certainly sell it....."Agilent : scopes for those with no time to think

I only had a quick glance at the video, and I agree, it's ridiculous. The first thing that comes to mind is why Agilent felt the need to compare their 2013 scope with a LeCroy scope that came out 8 years earlier and that in the meantime has been succeeded by two generations (WRXi-A, WR6zi).

The firmware on the LeCroy must have been pretty old as well. Notice how it says "LeCroy" in the corner, not "Teledyne LeCroy"?

I guess Agilent was well aware that they needed an 8yr old model to compare to as the WR6zi would have made their DSOX4k like a toy. Which it is compared to a WaveRunner, really, as the correct equivalent would be the WaveSurfer Series.

The other thing I noticed is the instable trigger on the LeCroy, which doesn't look right to me. I guess this guy in the video either has no clue or he deliberately tried to make a competitor look bad.

But overall I'm not surprised, that is exactly the type of crap that Agilent has pulled like forever.

To be fair I have seen some of this same bullshit comparison marketing from LeCroy as well....albeit slightly less ridiculous....

I can't say that I have seen anything even closely similar from LeCroy. In fact, I can't remember ever having seen a video where they "compare" their scope against a competitor's, they always only show their own scopes. Of course they make everything look easy and highlight their selling points (well, who doesn't, that's marketing). But that's about it.

The only place where I saw LeCroy talking about competitors' scopes were a few whitepapers like this:
http://cdn.teledynelecroy.com/files/whitepapers/wp_interpolation_102203.pdf
But even there I'd say it's far from the level of BS you'll find in almost any Agilent whitepaper. All the tests are well described, as are the results, and should be easily reproducable. Looks pretty reasonable to me.

I think there's a huge difference between selling your stuff by putting a positive spin on it and twisting reality up to borderline lying.

why can't these companies just show what they sell, what it does, how much it costs, and what the terms are....I already know what i need, without them telling me who else is doing what.....and then assuming I believe one word of it.  Save the money, discount the scope, give me a compelling incentive on that basis (value) and move on.... I already like your products Agilent and don't need a fluffer

I wonder the same. My pet peeves are "Request Quote" buttons. What is hell the problem with just listing how much the damn thing costs? Agilent has prices on the US site but on most variants for other countries (including the UK) all you get is "Request Quote". It's different if I want to order or negotiate but more often than not I find myself thinking that if I have to go through a sales droid to get a simple price that I rather not bother at all.

LeCroy's website is even worse. It lists the base price for some scopes but for everything else I have to through a quote request. Seriously? Why can I configure a luxury car online which comes with hundreds of options, but can't do the same for a scope?

And then there's Tek who's sales droids are even calling me when I dared to download some spec sheet or manual from their website. I guess they must be really desperate these days.

[Rupunzell]

That is not the way test gear was once sold. The hewlett packard or Tektronix sales folks would visit to chat about their latest offerings, bring in the demo as requested then answer ALL related questions to what is and what is not. And.. they did specials if that was a better T & M solution.

*Zero pressure sales..

*Vintage hewlett packard & Tektronix printed catalogs had the price of said instrument and accessories in print.

If there were problems, they were quickly resolved within the designed in limits of said test gear. Post sales support was often good to excellent and most of all had few if any "bugs" that were baked in requiring "updates" to exterminate said bugs. Test gear was expected to do their intended job, function as required with zero grief, day after day, year after year. Yes, they got their periodic calibration and maintenance to help them stay healthy as test gear was considered an investment back then.

That has all changed today to Buy It Now, then toss it out soon as it's out of warranty (Bean counters & investors kinda demand this today). Yes, technology and measurement needs move forward, but keeping perspective on what is actually needed to get that measurement and testing done -vs- the latest and greatest with every fantasy bell & whistle turned into reality in that new box is not always a good thing. Really a matter of knowing precisely what is needed -vs- what is nice to have under the light of an orange moon.



Bernice

I wonder the same. My pet peeves are "Request Quote" buttons. What is hell the problem with just listing how much the damn thing costs? Agilent has prices on the US site but on most variants for other countries (including the UK) all you get is "Request Quote". It's different if I want to order or negotiate but more often than not I find myself thinking that if I have to go through a sales droid to get a simple price that I rather not bother at all.

LeCroy's website is even worse. It lists the base price for some scopes but for everything else I have to through a quote request. Seriously? Why can I configure a luxury car online which comes with hundreds of options, but can't do the same for a scope?

And then there's Tek who's sales droids are even calling me when I dared to download some spec sheet or manual from their website. I guess they must be really desperate these days.

[joeqsmith]

That is not the way test gear was once sold.

Some of them still come on-site and leave the equipment with us.   I don't like Keysight tossing their sales like they did.  We had Copper Mountain in a while back.  Great presentation, spent the day going over their product.     

Looking at this particular DSO's dead time:

10GS/s, collecting 5Ms requires 640ms.   If the PCI bus could handle 60MB sustained, it would require 83ms to move the data or about 13% of the bus BW.   Say the Ethernet can move the data at 50Mb/s which is about what I was getting with the built in board.   So about 6.25MB/second.   Moving 5Ms will require about 800ms.     

If we want to handle the data and not miss any of the little data the DSO does happen to collect, the 100Mb won't cut it.     At 400Mb/s with the 1G Ethernet, this time drops to 100mS.  Maybe enough time to move the data to the modern PC, post process and display it.   

At 10GS/s and collecting 200Ks requires 35ms.   Staying with 60MB on the PCI bus, it would require 3.33ms or about 9.5% of the bus.  The Ethernet transfer would be about 32ms using 100Gb.

For 20GS/second collecting 32MS (max for this DSO) requires 9.486 seconds.    So that is 1.6 ms of data collected out of the 9.486 seconds of total data.    Using the same 60MB PCI BW, that's about 533.33ms to move this data.    Or about 5.6% of the PCI bus being used.   

So say 534.93 ms is used to collect the data and move it through the PCI bus to the PC.   There's 8.951 seconds to get the data onto the screen.   Keep in mind, there's no math enabled and only one channel is being used.

My old LeCroy Wavemaster 8500A has an Intel P4 2.533GHz with 512KB L2 cache and 2G of RAM installed.  It also has a SSD.

Today I pulled out an old Agilent Infiniium MSO8104A.  This DSO is a little newer but much lower end than the Wavemaster, maybe a 1/4 of the price.    It also uses XP-Pro.  It has an Intel Celeron D 3.20GHz  with 256K L2 cache.    Is has the original mechanical drive in it.     It does however come with a 1Gb Ethernet port.   

Both DSOs have the same FSB speed. 

I repeated the test on the Wavemaster collecting at 5GS/s, 5M samples.  This requires 531 ms.   
Using the Infiniium collecting at 4GS/s, 8.2M samples required 42 ms.    I was actually running some math on the Infiniium and still out performing the LeCroy.   

I tried to run an FFT with the Infiniium and see what it would display at the sample frequency.  They don't seem to allow you to do this.

[Wuerstchenhund]

My old LeCroy Wavemaster 8500A has an Intel P4 2.533GHz with 512KB L2 cache and 2G of RAM installed.  It also has a SSD.

If it's an 'A' then it also has an intel D865GCL mainboard with AGP.

Today I pulled out an old Agilent Infiniium MSO8104A.  This DSO is a little newer but much lower end than the Wavemaster, maybe a 1/4 of the price.    It also uses XP-Pro.  It has an Intel Celeron D 3.20GHz  with 256K L2 cache.    Is has the original mechanical drive in it.     It does however come with a 1Gb Ethernet port.   

What it also comes with is an Adlink M880 or intel D915GUX PCI Express mainboard (depending on the version of your scope) which both are PCI Express boards.

I repeated the test on the Wavemaster collecting at 5GS/s, 5M samples.  This requires 531 ms.   
Using the Infiniium collecting at 4GS/s, 8.2M samples required 42 ms.    I was actually running some math on the Infiniium and still out performing the LeCroy.

Not surprising when considering that the Agilent has a Gbit NIC which is connected via its's own PCI Express lane so doesn't affect the PCI bus that is used for the Acquisition system.

On the LeCroy the 100Mbps NIC also doesn't use the PCI bus, it's connected via CSA to the chipset.

It shouldn't really come as a surprise that just plugging in a PCI Gbit NIC won't give you the same performance.

The bottom line of all this is that if pulling sampling data out via network is of upmost importance for you then the WM8kA is simply the wrong scope, and plugging in some network card certainly won't change that. LeCroy's strenght lies in its internal processing capabilities, and that's why people buy them, not to be used as simple acquisition system for external processing. And really, if all you need is a sampling system that delivers the data to your PC as fast as possible then bench scopes are generally not a good choice, and you really should have a look at something like a PXI system which is much better for what you're trying to do.

I tried to run an FFT with the Infiniium and see what it would display at the sample frequency.  They don't seem to allow you to do this.

There's a lot of stuff you can't do on the Agilent that you can do on the LeCroy.

[Wuerstchenhund]

More Rigol DG1062z Square Wave Tests

Since the previous screenshots gave me eyesore (green on white, yuck!) I thought let's just re-do them. This time around however I not only tested at 1MHz and 25MHz but also at 5MHz, 10MHz, 15MHz and 20MHz.

As before the SA is an Agilent E7495B, the cable a Huber & Suhner Sucoflex 100 (up to 18GHz) and the BNC-to-N adapter a Huber & Suhner rated to 18GHz as well.

The various shots show how the square wave composition deteriorates with increasing frequency. The 1MHz one shows pretty much all the harmonics one expects, but at higher frequency this changes until at 25MHz it's essentially just a two tone signal.

[joeqsmith]

It shouldn't really come as a surprise that just plugging in a PCI Gbit NIC won't give you the same performance.

Just to be clear, when I was measuring the dead times of the two DSO's, Ethernet was not used.   I never looked at how fast I could pull data off the Agilent.   

The bottom line of all this is that if pulling sampling data out via network is of upmost importance for you then the WM8kA is simply the wrong scope, and plugging in some network card certainly won't change that. LeCroy's strenght lies in its internal processing capabilities, and that's why people buy them, not to be used as simple acquisition system for external processing. And really, if all you need is a sampling system that delivers the data to your PC as fast as possible then bench scopes are generally not a good choice, and you really should have a look at something like a PXI system which is much better for what you're trying to do.

To be clear, the Wavemasters software and PC are out dated and slow.  What would you expect for a 13 year old PC based instrument.   Using a faster Ethernet card on the PCI bus will improve download performance.     

The high end LeCroys do have some very impressive features when it comes to processing the data.   Even my old 7200 with its 68000 VME chassis has far more features than most low end modern DSOs.   Using these dated high end DSOs for home hobbies has been a blast.   LeCroy does not seem to hold a lot of resale value and as they age, like the old Wavemaster, the prices drop.   

I'm sure there are many reasons why people buy what they buy.   Personally I like seeing some of the old equipment in use and certainly am not going to put people down for how or why they do what they do.    I just enjoy the fact that so many of us enjoy playing with electronics and are willing to share there experiences.   

[Wuerstchenhund]

It shouldn't really come as a surprise that just plugging in a PCI Gbit NIC won't give you the same performance.

Just to be clear, when I was measuring the dead times of the two DSO's, Ethernet was not used.   I never looked at how fast I could pull data off the Agilent.   

Then I guess I misunderstood your post, for which I apologize.

To be clear, the Wavemasters software and PC are out dated and slow.  What would you expect for a 13 year old PC based instrument.

It doesn't have to be. If it's an 'A' model then the CPU can be upgraded to a P4 with 800MHz FSB and 1MB cache, and especially the cache helps as this is where X-Stream does all its calculations.

The software doesn't have to be old as well. On your videos I noticed that it still says "LeCroy" in the lower left corner which suggests that you're running a very old firmware. The WM8kA is still supported, and the latest software update came out just a couple of months ago, and will upgrade your scope to the same version that runs on the latest LeCroy scopes (although it won't also give you all new features of course).

Using a faster Ethernet card on the PCI bus will improve download performance.

Probably, but again it might still lead to side effects. If you didn't see any then good for you, but my point was that this doesn't mean there are none or that any such upgrades will be trouble-free (which often won't be).

The high end LeCroys do have some very impressive features when it comes to processing the data.   Even my old 7200 with its 68000 VME chassis has far more features than most low end modern DSOs.   Using these dated high end DSOs for home hobbies has been a blast.   LeCroy does not seem to hold a lot of resale value and as they age, like the old Wavemaster, the prices drop.   

That's true, although very high bandwidth scopes with 50ohms only inputs like the WaveMaster are generally cheaper as most people want 1M inputs and BNC. But I guess the main reason for used LeCroy scopes often being so cheap is that when thinking 'scope' most people think 'Tek' and 'Agilent', and for home users maybe 'Rigol' and 'Siglent' as well, but that's about it. LeCroy seems to be mostly overlooked on the second hand market, which is good as like you say it keeps prices low. And they did and still make some of the most advanced scopes on the market.

[Rupunzell]

BNC connectors do not work well above 3 Ghz, they will be pressed to achieve a return loss of better than 20db (their mechanical dimensions and stability is a significant part of this problem). Only the very best BNC connectors work to 4-5 Ghz and they might achieve 26db return loss.

To believe any BNC connector is rated and will function to 18Ghz is pure folly.

Cheap BNC connectors will be pressed to operate even to 1 Ghz.

If manufactures of this Ghz stuff is honest about Ghz performance, BNC connectors will not be used at all.


Beyond this, there is the common 50 ohm BNC connector and less common 75 ohm BNC connector which is somewhat compatible with the 50 ohm variety, but some 75 ohm BNC connectors are NOT compatible with 50 ohm BNC connectors.


Bernice

As before the SA is an Agilent E7495B, the cable a Huber & Suhner Sucoflex 100 (up to 18GHz) and the BNC-to-N adapter a Huber & Suhner rated to 18GHz as well.

[Wuerstchenhund]

BNC connectors do not work well above 3 Ghz, they will be pressed to achieve a return loss of better than 20db (their mechanical dimensions and stability is a significant part of this problem). Only the very best BNC connectors work to 4-5 Ghz and they might achieve 26db return loss.

Some modern higher bandwidth scopes use connectors that look like BNC (and are mechanically compatible) but aren't and work pretty well up to 10GHz. For example, the new Keysight MSO-S has such connectors, and this scope is rated to 8GHz.

I have some adapters that use similar connectors, and some are rated to 18GHz, although the loss above say 10GHz gets pretty high.

To believe any BNC connector is rated and will function to 18Ghz is pure folly.

No-one said anything about BNC being suitable to 18GHz.

[Rupunzell]

For those who want a DSO, get a LeCroy.

If 1 meg is needed at the probe tip, use an active probe with the 50 ohm input and accept the limitations of 1 meg ohm with X pF at the probe tip. Ghz instrumentation are 50 ohm input are a must if one is to be honest about dealing with the realities of Ghz capability.


Bernice

That's true, although very high bandwidth scopes with 50ohms only inputs like the WaveMaster are generally cheaper as most people want 1M inputs and BNC. But I guess the main reason for used LeCroy scopes often being so cheap is that when thinking 'scope' most people think 'Tek' and 'Agilent', and for home users maybe 'Rigol' and 'Siglent' as well, but that's about it. LeCroy seems to be mostly overlooked on the second hand market, which is good as like you say it keeps prices low. And they did and still make some of the most advanced scopes on the market.

[Rupunzell]

Any BNC at 10 Ghz, not gonna work. Any manufacture that rates their BNC to 18 Ghz is being extremely dis-honest and deceptive.


Bernice

I have some adapters that use similar connectors, and some are rated to 18GHz, although the loss above say 10GHz gets pretty high.

No-one said anything about BNC being suitable to 18GHz.

As before the SA is an Agilent E7495B, the cable a Huber & Suhner Sucoflex 100 (up to 18GHz) and the BNC-to-N adapter a Huber & Suhner rated to 18GHz as well.

[Wuerstchenhund]

Any BNC at 10 Ghz, not gonna work. Any manufacture that rates their BNC to 18 Ghz is being extremely dis-honest and deceptive.

Yeah, well, it seems you don't get what 'rated' means. If a part is 'rated' up to 18GHz it merely means that it's properties up to 18GHz are known. It doesn't necessarily mean 'guaranteed to work great at' or 'zero loss at'.

You can rate a piece of string to 100GHz, no problem. It doesn't mean it's any good at that frequency, though.

As to what the manufacturer rating is worth, I certainly wouldn't trust a cheap part from a Chinese ebay seller but I an tell you from quite a bit of personal experience that the stuff you get from manufacturers like Huber & Suhner is pretty much spot-on. In fact, Huber & Suhner is one of the most renowed manufacturers for RF cables and stuff, and that's for a reason.

[tautech]

Any BNC at 10 Ghz, not gonna work. Any manufacture that rates their BNC to 18 Ghz is being extremely dis-honest and deceptive.

Yeah, well, it seems you don't get what 'rated' means. If a part is 'rated' up to 18GHz it merely means that it's properties up to 18GHz are known. It doesn't necessarily mean 'guaranteed to work great at' or 'zero loss at'.

You can rate a piece of string to 100GHz, no problem. It doesn't mean it's any good at that frequency, though.

As to what the manufacturer rating is worth, I certainly wouldn't trust a cheap part from a Chinese ebay seller but I an tell you from quite a bit of personal experience that the stuff you get from manufacturers like Huber & Suhner is pretty much spot-on. In fact, Huber & Suhner is one of the most renowed manufacturers for RF cables and stuff, and that's for a reason.

While you are both to'ing and fro'ing somebody should state a load impedence which WILL make a massive difference at those frequencies.

[Wuerstchenhund]

LeCroy is not a mainstream brand.   When I think LeCroy, I think physics.  Well, not so much anymore.   My 7200 even has some support in the software for TOF.  Crude yes but the fact it has anything gives an idea of their target market back then.   

Was the same with me. I knew they existed but never considered them until two years ago when I had the chance to get a WaveRunner LT224 for cheap. Now I regret not having looked at their scopes earlier.

They still offer a 1Meg input driver but price for a few new ones was more than the Wavemaster cost.   

I see them occasionally on ebay, and usually for pretty excessive price tags.

I think LeCroy solved that pretty well with the current WavePro 7zi  and WaveMaster 8zi by giving each channel two inputs (ProLink and ProBus with BNC). Another solution I haven't seen anywhere else.

It would make the old Wavemaster more useful as a general purpose scope.   I was playing around with a  few different op-amps to make a driver for the it.  These videos show a few of them. 

Interesting. It would certainly make the scope more useful for common application, and they wouldn't have to go very high bandwidth-wise (i.e. 500MHz). You could stick them in the case of an old ProBus probe (incomplete active probes often come up for little money).

[Rupunzell]

Measure the return loss of that  Huber & Suhner adapter up to 18 Ghz, then we can discuss more. Manufactures can claim all kinds of what not, it is up to the user to verify their claims, not simply believe what is stated in print or advertised.



Bernice

Yeah, well, it seems you don't get what 'rated' means. If a part is 'rated' up to 18GHz it merely means that it's properties up to 18GHz are known. It doesn't necessarily mean 'guaranteed to work great at' or 'zero loss at'.

You can rate a piece of string to 100GHz, no problem. It doesn't mean it's any good at that frequency, though.

As to what the manufacturer rating is worth, I certainly wouldn't trust a cheap part from a Chinese ebay seller but I an tell you from quite a bit of personal experience that the stuff you get from manufacturers like Huber & Suhner is pretty much spot-on. In fact, Huber & Suhner is one of the most renowed manufacturers for RF cables and stuff, and that's for a reason.

[Rupunzell]

Load impedance is only part of a transmission line system.

Source impedance, termination-load impedance, connectors and transmission line all matter. If the currently common BNC worked past 110 Ghz, there would be no reason for connectors like N, TNC, SMC, SMB, SMA, WSMA, APC-7, APC-3.4, K, 2.92mm, 2.4mm, 1.85mm, V, and others.

When Ghz systems are discussed, connectors and the entire transmission line system performance matters.


Bernice

While you are both to'ing and fro'ing somebody should state a load impedence which WILL make a massive difference at those frequencies.

[tautech]

While you are both to'ing and fro'ing somebody should state a load impedence which WILL make a massive difference at those frequencies.

Load impedance is only part of a transmission line system.

Source impedance, termination-load impedance, connectors and transmission line all matter. If the currently common BNC worked past 110 Ghz, there would be no reason for connectors like N, TNC, SMC, SMB, SMA, WSMA, APC-7, APC-3.4, K, 2.92mm, 2.4mm, 1.85mm, V, and others.

When Ghz systems are discussed, connectors and the entire transmission line system performance matters.


Bernice

Exactly.
Thanks

[anotherlin]

Sorry for being late.

Here's 1V 1MHz square wave from a Hameg 8030-2 function generator module.
It's straight from the BNC output to 1:1 10MHz probes of a Hameg HMO722 scope.
Note that I'm running an old version of the firmware of the scope, but I don't think that changes things much.

The generator is pretty old, around end of the 80s. Fully analog with digital "metering".
It is capable of square, sine, and triangle, with a maximum of 1MHz.
I sold it about 2 weeks ago, so no more test possible.

I do have an Hameg 8130 generator (build 1993), which is more capable (10MHz max).
I will post captures shortly if you guys are interested.

[lincoln]

At risk of bringing back a zombie thread, I finally got a scope with some bandwidth.

Not so much a square wave but a pulse generator, rated at 350ps @ 25V, I have absolutely no use for this but it was dirt cheep off of ebay. I want to get some hardline to bridge the generator and attenuator together,

[MadTux]

Lol, that's basically a glorious Jim Williams pulse generator sold in a TM 5000 box, although the 50kHz rep rate generator is a nice addition to the original free running version, if you don't want too much jitter.

Please take the covers off, I'm seriously wondering how they managed to get 10m of coax charge line inside a TM 5000 box. The 60ns/15m delay line in the HP 215A fills the complete lower part of a 19" rack box.

[lincoln]

Lol, that's basically a glorious Jim Williams pulse generator sold in a TM 5000 box, although the 50kHz rep rate generator is a nice addition to the original free running version, if you don't want too much jitter.

Please take the covers off, I'm seriously wondering how they managed to get 10m of coax charge line inside a TM 5000 box. The 60ns/15m delay line in the HP 215A fills the complete lower part of a 19" rack box.

Here is the album: http://imgur.com/jYPxmTx,YdjCfHB,dmWnbBR,CYQqv9x

the attenuator has GPIB and there are two tiny jumper (in addition to the coax) that bridge the two that lets you control the fine amplitude adjustment and suppress pulses.... I'm not allowed on ebay any more.

[MadTux]

Thanks for the pictures. I'm always curious how test gear looks from the inside.

[tautech]

While nothing to get real excited about, I don't remember a Siglent SDG5082 square wave posted here.
Had one of these through my hands today, quite liked it, nice UI.

As in all my prevoius posts:
50 Ohm source and internal termination.
1 m RG58
Scope SDS2304

30 MHz @ 40% duty, 70 mV P-P

[rolycat]

Couldn't find any posts for the Tek MDO3000 series, so:

A 25 MHz square wave from the AFG on an MDO3054 to the same scope.
Connection is 0.5 m RG58, 50 ohm source and internal termination.

A nice clean signal with a decent rise time and low jitter.

[mmagin]

HP 209A ($110 from ebay, seems to work perfectly) at its maximum 2 Mhz, connected to HP 54645A scope with banana-bnc adapter, coax, and 50 ohm termination, scope plotting over gpib - still figuring that out -- those rectangles should be squares
  This is a little better.

I will follow up somewhat later with the results of a 74LVC sine-to-square converter connected to my gpsdo 10mhz source.  I need more amplitude into my 35 year old microwave frequency counter's ref input.

[Howardlong]

Finally got around to setting up my 54120B on the bench, first time using this scope, this is what I got up and running about five minutes from switching on. I'm using a 54121A TDR test set with a short on the TDR/Ch1 channel for the pulse. Total of $700 of TE from ebay, in three separate auctions for the 54120B, 54121A and interconnecting cable, the cable cost almost as much as the 54120B.

I suspect once I figure out what I'm doing with this scope I might be able to improve on it.

[modrobert]

HP 1660AS with cheap passive probe, signal from Spartan-3 XC3S400 FPGA, using DCM to generate pulses.

[Howardlong]

I did a new video yesterday on measuring rise times of external signals with an HP 54121T sampling scope setup (comprises of a 54120B mainframe, 54121A four channel 20GHz test set and an umbilical) plus some external plumbing. Unlike sampling scopes that use a random sampling approach, the 54121T requires a delay line to be able to see the trigger. Sorry the focus wasn't quite the best but hopefully it's good enough.



An earlier video I did on this scope here:

[TheSteve]

First pic is 15 MHz from Agilent 81104A pulse/pattern generator top, Agilent 33120A middle and Rigol DS1074Z-S bottom.

Second pic is the 81104A at 40 MHz
Third is 81104A at 60 MHz
Forth is 81104A at 80 MHz
Fifth is 81104A at 85 Mhz(this is technically over range as the 81104A is only spec'd to 80 MHz

All shots are from TDS7104 terminated with 50 ohms.
Poor Agilent 33120A probably shouldn't be spec'd to 15 MHz for a square wave...

[EV]

Here are pictures of100 MHz and 250 MHz square waves from Tektronix PG502 pulse generator. The scope is Tek R7633 with 7S12, S-6 and s-53 plug ins.

[tggzzz]

I picked up a couple of Tektronix 1502 TDRs for £20 each at an auction, not expecting them to work, but hoping that I would be able to make a frankenmachine. After creating a fake battery one did work, and the results are shown below.

So, what's the risetime? The manual state the tunnel diode output should have a risetime of "around 50ps" and a "system reflected risetime of 140ps or less". Another source states the TD risetime is 35ps. The amplitude is around 225mV.

The display is nominally 0.025m/div for a "solid poly" dielectric velocity factor 0.66, so 1 div ~= 125ps. The measured risetime is about 0.5div, or 60ps. Note that no tweaking nor calibration has been done, but comparing the display with measurements of a cable's length, it looks pretty accurate.

Not bad for a £20 instrument first introduced in 1975.

[TheSteve]

Picked up an HP 8080A mainframe with a 8093A 1 GHz rate generator and two 8093A output modules from ebay.

Here are some square waves - 100 MHz and 200 MHz on my Keysight DSOX3014A(born @ 100 MHz, but modded to 500+ MHz)
The DSOX3014A is looking at both outputs at once.

And 300 MHz and 625 MHz on my Tek TDS7104A - the 625 MHz was cheating though - the frequency is real as is rise time but the frequency was selected because the reflections make the wave form look reasonably square.

[tggzzz]

Finally got around to setting up my 54120B on the bench, first time using this scope, this is what I got up and running about five minutes from switching on. I'm using a 54121A TDR test set with a short on the TDR/Ch1 channel for the pulse. Total of $700 of TE from ebay, in three separate auctions for the 54120B, 54121A and interconnecting cable, the cable cost almost as much as the 54120B.

Nice scope, which brings back fond memories of using them when they were the dog's bollocks, and of chatting with the digitiser's creator. They are still useful on this forum, since they are a clear demonstration that the "samples/s" spec is completely different to the "front end MHz" spec

If somebody wants a source with ~50ps risetime, there's a working Tektronix 1502 available on ebay at the moment (no affiliation). They are sweet little things, being portable (smaller than a Tek 465), battery powered, and waterproof - iff you follow the full instructions when putting the case back together!

For more pics of my 1502 (not the one on ebay), see my earlier reply #331 or https://www.eevblog.com/forum/rf-microwave/tdr-for-measuring-cablesconnectors-what-is-it-worth-to-radio-hams/msg1025046/#msg1025046

[Howardlong]

Finally got around to setting up my 54120B on the bench, first time using this scope, this is what I got up and running about five minutes from switching on. I'm using a 54121A TDR test set with a short on the TDR/Ch1 channel for the pulse. Total of $700 of TE from ebay, in three separate auctions for the 54120B, 54121A and interconnecting cable, the cable cost almost as much as the 54120B.

Nice scope, which brings back fond memories of using them when they were the dog's bollocks, and of chatting with the digitiser's creator. They are still useful on this forum, since they are a clear demonstration that the "samples/s" spec is completely different to the "front end MHz" spec

Unfortunately, for directly measuring eye diagrams of many of today's high speed interfaces such as USB 3.x and HDMI, I find the 54120B and its additional modules less than perfect.

The problem is that the p-p voltages are fairly low, and typically you need to split off the signal you're measuring into both a scope channel and the trigger input. If your signal has a longer term DC component in it (or is bursty) then you need to use a resistive power splitter to maintain DC adding to your probe loss, so that's typically 26dB down in total with a typical x10 probe. When the single ended p-p is only 300mV or so, that doesn't leave much for the scope's channel front end.

If you use a directional coupler to reduce losses into the channel input, with the trigger sampling off the coupled port, then that improves things a bit but only if the signal has no DC component: the coupled port will be AC coupled so this will show up as jitter on signals with much DC component.

At least with HDMI there is a clock/10 signal, so using that to trigger is usually a reasonable option but it makes casual browser probing much harder as you're almost certainly going to have to solder in a tap to make it work logistically.

Still, the biggest problem is that the scope front end lacks sensitivity for a lot practical use cases on many of today's low level high speed serial signals. Sure, you could add a broadband amplifier block, but that in itself introduces its own problems, not least that you're no longer measuring the actual signal.

[tggzzz]

Finally got around to setting up my 54120B on the bench, first time using this scope, this is what I got up and running about five minutes from switching on. I'm using a 54121A TDR test set with a short on the TDR/Ch1 channel for the pulse. Total of $700 of TE from ebay, in three separate auctions for the 54120B, 54121A and interconnecting cable, the cable cost almost as much as the 54120B.

Nice scope, which brings back fond memories of using them when they were the dog's bollocks, and of chatting with the digitiser's creator. They are still useful on this forum, since they are a clear demonstration that the "samples/s" spec is completely different to the "front end MHz" spec

Unfortunately, for directly measuring eye diagrams of many of today's high speed interfaces such as USB 3.x and HDMI, I find the 54120B and its additional modules less than perfect.

The problem is that the p-p voltages are fairly low, and typically you need to split off the signal you're measuring into both a scope channel and the trigger input. If your signal has a longer term DC component in it (or is bursty) then you need to use a resistive power splitter to maintain DC adding to your probe loss, so that's typically 26dB down in total with a typical x10 probe. When the single ended p-p is only 300mV or so, that doesn't leave much for the scope's channel front end.

If you use a directional coupler to reduce losses into the channel input, with the trigger sampling off the coupled port, then that improves things a bit but only if the signal has no DC component: the coupled port will be AC coupled so this will show up as jitter on signals with much DC component.

At least with HDMI there is a clock/10 signal, so using that to trigger is usually a reasonable option but it makes casual browser probing much harder as you're almost certainly going to have to solder in a tap to make it work logistically.

Still, the biggest problem is that the scope front end lacks sensitivity for a lot practical use cases on many of today's low level high speed serial signals. Sure, you could add a broadband amplifier block, but that in itself introduces its own problems, not least that you're no longer measuring the actual signal.

I agree with all that, of course.

I'll question the concept of "casual browser probing" at such baud rates and with differential signals. I still like Z0 probes, and the fact that I no longer have access to modern megabuck probes has no relevance to that. Oh no, not at all

[med6753]

I'll play. Source: Heath IG-4244 Oscilloscope Calibrator. Display: Tek 2465 (50 ohm input)

[TiN]

Upgraded/downgraded my scope at work. Not a fan of new Tek UI, so much button dodging and multilevel menus..  Old Windows/PPC-based TDS5034B was sorta easier.

Square wave measure of own calibration output in the TDS7704B : ~260ps into 50Ohm.
Brand new MDO4054C with same 1:1 BNC cable measuring same cal output of TDS7704B : ~800ps into 50 Ohm.

[tggzzz]

Output from a Tek 1502 TDR driving a Tek 485, Tek 2465, and Tek 2445B, all terminated with an internally with 50ohms. The Tek 1502 risetime is ~50ps, and the Tek 485 timebase is 1ns/div with a risetime of ~900ps.

The Tek 1502 output shows two clear phases

• one in which it determines the "bias point" of the tunnel diode
• the other in which is biassed to just below that point and then triggered to produce the pulse that is measured

Given the duration of each phase, 37us, it is a testament to the Tek engineers of >40 years ago that the 1ns edge is so clearly visible.

[lty1993]

Source:
1. Rigol MSO2302A-S Internal Source (Attachment 1) [15Mhz]
2. Rigol DG4202 (Attachment 2 and 3) [25Mhz and 60Mhz]

Display:
1. Rigol MSO2302A-S

Direct Coax and 50Ohms load.

[guenthert]

For contrast and completeness' sake below results I got from an Analog Discovery 2 with the BNC adapter module:
(output shunted with built-in 50Ohm terminator, set 1V symmetric square wave)
input was not terminated (uses ~1MOhm "high impedance" input, DC coupled)

top to bottom:

- 8' BNC cable, 5MHz (the signal generator offers 10MHz, but then not much of a square is left)
- 8' BNC cable, 1MHz
- 100MHz 10x probe, 1MHz (system is in a bit of a noisy environment, I think the probe picks up some RFI)
- 100MHz 10x probe, 5MHz
- 8' BNC cable, input terminated via T-piece and 50Ohm terminator, 5MHz
- FFT of the last one

[capt bullshot]

I believe, it's been done before, but I did hack a few components together to produce a quite nice square wave. The basic concept is a HC14 oscillating at a non important frequency and driving a LVPECL level translator. It's outputs have emitter resistors of 100R to GND, and AC coupled (10uF || 100nF) to a back terminated 50 Ohm line (Rs = 43R according to the OnSemi application note. Running some RG174 to the 50R scope input shows a clean trace, the scope reads about 300ps rise/fall time (I don't have access to a faster than 1GHz scope). So nothing very exiting, but easy to build, took about one hour to complete.

[Howardlong]

What's the prototyping board you're using?

[capt bullshot]

This is a SP3T-50x50-G from BusBoard Prototype Systems. It has a copper plane on the bottom side, 50x50 mils pads on the top side and non-plated holes every fifth pad or so. It is a thin PCB, can be cut using a paper scissor.

 

[jpb]

I've been using the LTC6957 demo board. Unfortunately I'm in the middle of moving house (again) so everything is packed up so can't show anything other than this very bad photo.

The rise times for LVCMOS output is around 700 to 800 psecs and much less for the LVPECL version.

http://www.linear.com/product/LTC6957-1

[Howardlong]

This is a SP3T-50x50-G from BusBoard Prototype Systems. It has a copper plane on the bottom side, 50x50 mils pads on the top side and non-plated holes every fifth pad or so. It is a thin PCB, can be cut using a paper scissor.

Very nice, I'm sure I'll be adding a couple of those onto my next Mouser order.

Edit: do they spec the Er?

[capt bullshot]

Edit: do they spec the Er?

No, afaik

[tggzzz]

This is a SP3T-50x50-G from BusBoard Prototype Systems. It has a copper plane on the bottom side, 50x50 mils pads on the top side and non-plated holes every fifth pad or so. It is a thin PCB, can be cut using a paper scissor.

Very nice, I'm sure I'll be adding a couple of those onto my next Mouser order.

Edit: do they spec the Er?

I would have thought that the variability of anything you would use as conductors on the topside would be more significant than the likely difference in Er. I'd simply assume 4.2.

[sorenkir]

Hi,

I have discovered that BG7TBL's 35M-4.4G USB Signal Source (based on ADF4351) generates a quite nice square wave with fast edges around 200ps.
Measured with my TDS520B-500MHz (in fact ~650MHz --> Tr=~538ps)

Michel.

[Muxr]

Don't really have a fast pulse generator, but I can show some relatively fast rise time on my RF gen.. as captured by the RTM 1054

I can reliably see the signal up to 1.2Ghz.. even up to 1.8Ghz is somewhat visible but the trigger starts failing pretty often at that frequency.

[AlphaRomeo]

Thank you all for the postings.  I just got the Siglent SDG2042X, at 1Mhz the square wave is acceptable,  at 5Mhz starting to degrade very bad, etc. I thought I got a defective device. I need to dig more into how these things works. How the square wave is generated, etc. Reading your post helped me understand  that I did not get a defective generator.

[MrW0lf]

Thank you all for the postings.  I just got the Siglent SDG2042X, at 1Mhz the square wave is acceptable,  at 5Mhz starting to degrade very bad, etc.

Might get better results with ARB mode=DDS and using square from built in ARB wfms.

[ADT123]

Heard a colleague say "now that's a fast edge"

[amspire]

ADT123,

was that sampling scopes one of your projects? Having a go at building a sampling scope has always been something I have wanted to try. The principles are so simple, but I am sure it took a massive effort to get that 25MHz bandwidth. The waveform really is amazingly clean.

Historically, this is the technology that allowed scopes to be built with GHz bandwidths when scope mainframes were struggling to reach even 1 MHz bandwidth.

A pity the price is so out of reach of the hobbyist. I have always thought this is potentially a very cheap technology if the market was big enough - maybe not for 25GHz, but 5GHz bandwidth would be pretty good. 

Am I delusional? 

Richard.

[WackyGerman]

Here are my results of measuring a 10 MHz squarewave from my Siglent SDG1010 with three different bnc cables .

[MrW0lf]

I know nothing about tech side... but as a concept, maybe it is possible to hack analog frontend of cheap USB scope having ETS? For example ~100EUR Pico 2204A has 2GSa/s ETS listed. Logically software is there, timing stuff is there...

[Electro Fan]

Heard a colleague say "now that's a fast edge"

That looks like a fast rise time but to keep things apples to apples most of the measurements here have been at 10% and 90% rather than 20% and 80%.

[ADT123]

Richard - I designed most of the real time scopes with a parallel port starting with the ADC-10 in 1991 and hung up my soldering iron around 2001 with the ADC212/100 which included repetitive ETS sampling (https://www.picotech.com/about/history).

As for a lower cost / lower bandwidth sampling scope its an interesting idea.  Above a few GHz every component gets expensive if you want to do the job properly (connectors, PCB etc) but below say 5GHz things get a lot cheaper.  Will have a think.  Guess it depends on the market - hobby users often go for 2nd hand boat anchors which can be cheap and to be honest not everyone knows how to drive a sampling scope (splitters for trigger signals etc).

10/90 vs 20/80 rise time - thats a fair cop.  I just borrowed a waveform so when I get a chance will see if I can do better.

[pigrew]

Tabor 8025, programmed to be 1Vpp, 50 MHz, 50 ohm terminated. 10%/90% rise time is 5.2ns, fall is 4.65ns.

[ADT123]

10/90 rise time (see comment from Electro Fan a couple of posts again).  Scope rise time is 14ps, pulse rise time is 10ps.  Combined gives 18.74ps.

Please dont try to beat this - not sure I can respond with anything faster!

[MrW0lf]

Noticed that on last Pico screenshot sampling rate is mere 10TSa/s, while on previous 16TSa/s But guess both are adequate being "slightly" over Nyquist

[Electro Fan]

10/90 rise time (see comment from Electro Fan a couple of posts again).  Scope rise time is 14ps, pulse rise time is 10ps.  Combined gives 18.74ps.

Please dont try to beat this - not sure I can respond with anything faster!

It is very competitive with the best rise time we have previously seen (~16ps by EV):

https://www.eevblog.com/forum/testgear/40-ps-rise-time/msg935446/#msg935446

[Electro Fan]

Maybe someone can show us a sub picosecond rise time?

[Joel_l]

Not fast - Siglent SDG5082

50 Ohm output, 50Ohm pass through terminator on scope.

[Electro Fan]

10/90 rise time (see comment from Electro Fan a couple of posts again).  Scope rise time is 14ps, pulse rise time is 10ps.  Combined gives 18.74ps.

Please dont try to beat this - not sure I can respond with anything faster!

It is very competitive with the best rise time we have previously seen (~16ps by EV):

https://www.eevblog.com/forum/testgear/40-ps-rise-time/msg935446/#msg935446

Looks like I missed a faster contestant:  (5.22ps by Hugoneus/Shahriar)
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg592751/#msg592751

[TheSteve]

Not too horrible for ECL logic feeding multiple sources.

[R_G_B_]

https://youtu.be/ACUbBUydgUQ

[JPortici]

Finally the thing is repaired and i can play at this game too


unfortunately, the fastest thing i got at hand is the trigger output of a rigol scope, just under 1ns rise/fall time

well there is the 250 MHz ECL clock for the plugins.. and one has to be serviced......

[Leo Bodnar]

Also there are other sampler topologies that rely less on the matching of the components so that may be interesting to pursue.  I am not quite sure why Tek for instance only made a couple of samplers based on the travelling wave gate concept and used bridges for others.  It seems like it would be interesting to try a travelling wave design.

All Tek electrical sampling heads for 11800 and perhaps TDS8000 series scopes are based on what used to be called "travelling wave gate" in 11000 series (like S-4.) 
You can see them six sampling diodes here in the SD-26 sampling hybrid.
Leo

[David Hess]

Also there are other sampler topologies that rely less on the matching of the components so that may be interesting to pursue.  I am not quite sure why Tek for instance only made a couple of samplers based on the travelling wave gate concept and used bridges for others.  It seems like it would be interesting to try a travelling wave design.

All Tek electrical sampling heads for 11800 and perhaps TDS8000 series scopes are based on what used to be called "travelling wave gate" in 11000 series (like S-4.) 
You can see them six sampling diodes here in the SD-26 sampling hybrid.
Leo

I think the traveling wave gate design still depends on matching and at least in my experience with the S-4, seems to suffer from more problems with blow-by.

As for a lower cost / lower bandwidth sampling scope its an interesting idea.  Above a few GHz every component gets expensive if you want to do the job properly (connectors, PCB etc) but below say 5GHz things get a lot cheaper.  Will have a think.  Guess it depends on the market - hobby users often go for 2nd hand boat anchors which can be cheap and to be honest not everyone knows how to drive a sampling scope (splitters for trigger signals etc).

The report I have of a rebuilt Tektronix S-2 sampling head with cheap microwave schottky diodes from Avago was a improvement in bandwidth from roughly 4 to 8 GHz.  Tektronix used an RF substrate in that design but it was barely surface mount.

For signal integrity applications there are no special triggering requirements unless a clock is not available.  But the S-2 has an internal trigger pickoff so even that is not an issue.  Sampling the leading edge is of course a different matter requiring a delay line, pretrigger signal, or random sampling.

I am inclined to think the random sampling is the best way for ease of use however it makes for a very complex timebase and it does not work well with internal triggering.

[Leo Bodnar]

I think the traveling wave gate design still depends on matching and at least in my experience with the S-4, seems to suffer from more problems with blow-by.

To some extent all balanced samplers rely on matching the top and bottom paths - both in component parameters and electrical layout.  Travelling wave gate sampling aperture depends on physical distance between the middle and outside sampling diodes and on, say, SD-26 it is less than 1mm.  I won't be surprised if even diode bonding point position is critical.

I could not find any evidence of blowby compensation in SD-24 and SD-26 heads.  However, according to 11800 documentation some heads do have it.

[nctnico]

ADF5341 ADF4351 + Agilent 54845A:


Edit: changed part number.

[Howardlong]

ADF5341 + Agilent 54845A:

Nice, not sure about the part number ADF5341 though?

[David Hess]

That is very interesting about the rebuilt S-2 head working at 8 GHz with the Avago schottky diodes.  Would I be correct to assume that those were SMD packaged devices (e.g. 0201 / 0402 imperial) as opposed to something more exotic like beam lead or wire bonded die that someone managed to retrofit?

The replacement Avago schottky diodes were SOT-23 sized devices but the original diodes in the S-1 and S-2 samplers were not any smaller.

It seems like reverse leakage current is a bit high for many of the RF Schottky devices so I suppose that putting them in series with some slower but low leakage diode could be worthwhile to avoid the integration signal from degrading so much due to reverse biased diode leakage during the "hold" interval.

The measurement of the stored charge happens pretty quickly and the result is placed into a much slower but lower drift sample and hold so I do not think the leakage is a problem.

Random sampling shouldn't be that hard to get going up to a point, I guess it all depends in part on how many ps resolution you want to achieve in your sample acquisition window timing with the bar being raised for every few GHz you want the thing to perform well at.  4 GHz/250ps per cycle not quite so hard, 10 GHz quite a bit more challenging.

It has been a while since I have looked at it but I think the difference is that random sampling requires a timing measurement while sequential sampling can get away without that so the conditions are more controlled.  In practice, random sampling seems to have about twice the measurement jitter.

Say one thing I have wondered about is whether any "non exotic" (read hard to source, expensive) sampler related components (IC scale) exist?  I've heard of such being made in academic projects and from instrumentation vendors like PSPL and so on.  But just for an integrated T/H / S/H / sampler component it would seem like one might find something from the likes of Analog Devices/Hittite, MACOM, or whatever.  Of course if one is willing to spend enough money (hundreds of dollars ++) one can get ADCs with GHz level sampling capabilities and small sampling apertures that are used for undersampling types of applications, but I would have expected something simpler and less integrated and much less costly to exist.  Does it?  Mixers exist, not clear which if any would be applicable even with somewhat larger input signals.  Haven't noticed S/H T/H with ps scale apertures not integrated into ADCs or exotic instrument modules.

I am not aware of any such thing.  The closest I might have seen are diode bridge phase detectors.

[Leo Bodnar]

Here is Tektronix SD-30 40GHz frontend with 8.8ps risetime from early 1990's to add to the party.

Interesting shape of clipping lines.

Signal-facing part is not even ceramic - but some sort of glass.

Those skilled in the art will notice that critical dimension that defines the travelling wave sampler bandwidth is reduced to the minimum.

Leo

[darrell]

It's not actually 100 Hz, but 1.0000001 GHz sampled at 125 MHz causing the sample point to scan the waveform at 100 Hz. Scope probes are on the output of the 2 diode sampler hybrid in an HP VNA  (26.5 GHz). The source is squared up by an MGF4941 GaAs FET and fed via a 20 dB pad directly to a sampler. The ringing on the bottom which is likely due to the bias inductor and DC block capacitor. Fall time is about 45 ps which is probably due to the FET which has -3 dB gain point of about 9 GHz. Any ideas on a faster rise time source?

[qu1j0t3]

This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.

On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.

The primer:
http://cp.literature.agilent.com/litweb/pdf/5989-5733EN.pdf

^ This link is now dead. LabSpokane, do you know any other sources for the document? (And what is the document?)

Thanks

[Howardlong]

This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.

On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.

The primer:
http://cp.literature.agilent.com/litweb/pdf/5989-5733EN.pdf

^ This link is now dead. LabSpokane, do you know any other sources for the document? (And what is the document?)

Thanks

Keysight rebranded version here http://literature.cdn.keysight.com/litweb/pdf/5989-5733EN.pdf

[Insatman]

+5V out, battery powered reed pulser for use as a TDR, pulse calibration or just for frequency response testing.  <400ps Trise

[Insatman]

Adjustable voltage/polarity version of reed pulser.  This one can output from 2V to ~130V positive or negative.  Risetime is a bit longer.  My attempt at making something like the old TEK109 for use in my home lab.

[T3sl4co1l]

Hmm, it's not a coaxial relay, is it?

Tim

[David Hess]

I have thought about trying to make one of those with a mercury wetted reed relay mounted coaxial inside of a brass tube or as a coplanar waveguide to make it part of the 50 ohm transmission line.  Tektronix did this sort of thing for their fastest tunnel diode pulsers.  The Tektronix 7T11 sampling sweep uses this sort of construction for its wide bandwidth trigger circuits.

But most of the high bandwidth oscilloscopes that I would use it for are analog so the low repetition rate becomes a problem.

[Insatman]

sort of coaxial...it's a COTO 9000 series coaxial shielded relay.  In the low voltage version the relay is soldered as close to the BNC connectors as I could manage.  In the slightly slower high voltage version the relay is connected using a socket for easy replacement.  This increases the inductance a bit. 

When I swapped out the coaxial version for a non-coaxial version the rise-time did not change much as the ground is also carried across by my socket arrangement.  I built the larger version with a socket so I could experiment with different relays.   What I also found out is that over driving the relay coil helps with contact bounce. 

I also found that these particular COTO relays can't handle the 1000kV charge voltage I was hoping to use.  Still, 100V into 50ohms is more than enough for the work I am doing. 

[Insatman]

You can get a few 10's of Hz out of these relays.  I set mine to run at single shot or ~10Hz switch selectable.  I tested it up to 30Hz with no difficulties.  COTO claims up to 1x10^9 operations, but I think switching 50ohm circuits will likely degrade this significantly.   I have yet to wear one out however.

[MrW0lf]

Keysight U1282A 2.4kHz, 50% duty into 600 ohms.





Otherwise nice but hydraulic press channel dude should deal with these parasitic spikes.

[RedDogAlpha]

This is a great insight for someone green! Thanks for the post.

[qu1j0t3]

1 kHz and 1 MHz generated by Arduino Duemilanove (program below); a little interference from 16MHz device clock is clear in the 1MHz trace. Rise/fall ~ 19ns.

Scopes: Tektronix TDS 460A (display in "High Res" mode) and HP 1741A (Conv mode).

Code: [Select]

void setup() {
  // for ~ 1 kHz output on PWM pin 9 (OC1A)
  pinMode(9, OUTPUT);

  TCCR1A = (1 << COM1A0); // toggle OC1A on compare match
  TCCR1C = 0;
  TCCR1B = (1 << CS12) | (1 << WGM12);  // clkIO/256 prescaler; clear on timer compare
  OCR1A = 30; // ~ 1 kHz
  TIMSK1 = 0; //(1 << OCIE1A); // set output compare A match interrupt enable

  // ~ 1 MHz on OC0A (digital pin 6)
  pinMode(6, OUTPUT);

  TCCR0A = (1 << COM0A0) | (1 << WGM01); // toggle OC0A on compare match; clear on timer compare
  OCR0A = 7;
  TCCR0B = (1 << CS00); // no prescaler
}

void loop() {
}


[taydin]

10 MHz clock output from my agilent pattern generator, measured directly at the clock pod with the spring ground lead that wraps around probe tip:

[Physikfan]

Here are square waves 32 MHz, 300 MHz and 2.6 GHz of a HP8133A
measured by a Tektronix TDS820, 6 GHz oscilloscope with 44 ps rise time:

Square wave 32 MHz of the HP8133A, x-axis 5ns/div, y-axis 200mV/div:


Square wave 300 MHz of the HP8133A, x-axis 500ps/div, y-axis 200mV/div:


Square wave 2.6 GHz of the HP8133A, x-axis 100ps/div, y-axis 200mV/div:


The rise time displayed in the last image is about 60 ps

[HighVoltage]

I just came across this old Tektronix video from 1961, explaining really nicely about the square wave.
This might be a real good video for the young players...
The Square Wave 1961

[Tomorokoshi]

That's not a square wave...

That's a square wave.

[gf]

A 10MHz square wave from the built-in DDS of my Hantek 6074BD USB oscilloscope, displayed on the same oscilloscope. Directly connected with a coax cable, with external 50Ohm terminator at the scope. The DDS is specified DC~25MHz, using a DAC clock of 200 MHz. The rise time approximately reflects the 25MHz bandwidth limit of the function generator. All in all not spectacular.

The 2nd image shows the same same signal, but at a low amplitude of 10mV. The apparent ripple can hardly be overlooked.  A FFT from this signal shows a decent peak at 200MHz, so I'm pretty confident that we see the DDS clock, leaking through to the signal output In reality, the ripple amplitude is likely even higher, since the scope's analog bandwidth is only 70MHz.

[tggzzz]

OK, here's the edges from a very simple pulse generator:

• the source is 5V with no load, but obviously it is used to drive 2.5V into the scopes' 50ohm input
• 4GHz LeCroy HDO4904, connected directly to the scope input with a BNCfemale-BNCfemale adaptor
• 1GHz Agilent MSOS104A, connected via a 1m piece of coax of untested quality

It looks like the 10%-90% risetime is 256ps with a 6.3% overshoot, and the falltime is 453ps with a 3.8% overshoot.

Considering the simplicity of the circuit, that is remarkably fast. It is a simple demonstration that modern jellybean logic (74LVC1G*) generates significant power into the microwave waveband - and hence RF practices are appropriate.

In this circuit a major contributor to the performance is the decoupling capactors, especially the 0V/5V planes and short wide wires, and not forgetting that MLCCs have a very significantly reduced capacitance when there's a DC bias voltage.

My apologies for the quality of the photos; they had to be taken relatively quickly and in non-ideal conditions.

[MaxFrister]

Measurements Corporation Model 71 Square Wave Generator displayed on a Hewlett Packard model 122AR.

[T3sl4co1l]

Weird, the sweep linearity on that scope seems to be wrong?

Tim

[Microcheap]

Only fine equipment in this thread so I've decided to bring some "toys" to compare. The first is an unlocked Hantek HDG2002B, the output is a 15MHz 2Vpp signal with a 50ohm pass through terminator on scope and then a 1MHz signal directly connected on the scope using a BNC cable.
The second function generator is a MHS-5200A, both signal showed are connected to the scope with a BNC cable only.

[dzseki]

Source for all tests below: EMG 12563 (an old hungarian made) ECL pulse generator the rise time was measured to be 425ps (including the scope's self rise time) with a LeCroy WavePro 725 2.5GHz 40GS/s scope. The interconnect cable was (the same for all testing) a vintage Amphenol RG223U coax 1m long.

Yokogawa DL1740 4CH 1Gs/s 500MHz:

HP 54503A 4CH 20Ms/s 500MHz, the measured rise time varies somewhat between the channels, but for the good...

[0culus]

Here's a frequency domain 10 MHz square wave from my 3325B, showing the harmonics tapering off in power out to around 330-340 MHz.

[dzseki]

Looking at the manual, are they saying <1.5ns for the edge rate? 
http://www.emg.hu/gepkonyvek/EMG_12563.pdf

That is for the trigger output, for the main output they say <1ns.
Here is a fresh shot, although my HP 1720A does not feel very well today...
The first rise is the trigger output of the EMG 12563, the second rise is the main output, the time base was set to 2ns/div. Unfortunately even the main output is measured beyond 1.6ns this time.
Anyway the trigger rise time is not that far behind, and considering that it also has a selectable amplitude between 1V (in reality 1.5V terminated) or 100mV and a fixed 50% duty cycle it is very much usable even alone.

[MarkL]

Here's something a little different.

Here's a picture of the eye scan tool on an Agilent 16702B logic analyzer with a 16756A analysis card and E5382 probe.  It's looking at the output of an Analog Devices SiGe ADCMP580 comparator eval board.

The ADCMP580 has a rise/fall of 37ps (typ.) for 20% to 80%.  Applying a simple extrapolation puts it around 50ps for 10% to 90%.

The eye scan has a slope tool which I've placed at 10% and 90% in the center of the transition area.  The time difference between the two markers is 130ps.

So, that would give the analyzer an estimated rise time of sqrt(130ps**2 - 50ps**2) = 120ps, and a BW somewhere around 2.9GHz.  The analyzer datasheet says 2.33GHz, so I guess it's not too far off.

It works but it makes a really lousy sampling oscilloscope.  It took several minutes to gather all these data points (180M samples, if I'm reading the stats right).  The clock rate was 100MHz.

[David Hess]

That reminds me of the testing I did adding a pretrigger to my PG506.  The fast rise output shown below was taken with a Tektronix 7T11A in sequential sampling mode and a 14GHz S-4 sampling head through 1 or 2 nanoseconds, I forget, of RG400 cable on a analog storage 7834 mainframe.  The photograph was processed to produce inverse gray scale to make it suitable for printing.

The edge itself is almost perfect with a transition time of about 550 picoseconds.  This particular S-4 sampling head suffers from excessive blow-by this is not visible at this time scale.  The tilt may be due to dribble up in the RG400 cable; I did not notice it at the time or I would have verified if that was the case.

The massive amount of pattern dependent jitter is caused by supply voltage variation caused by the TTL counter chain inside the PG506 getting into the TTL based 75 nanosecond pretrigger delay circuit.  This was unnoticeable on a typical oscilloscope of up to 300MHz bandwidth; a 500MHz DSO might just see it.  This circuit would need to be corrected to be usable for its intended application but it serves as a lesson as to why single ended logic including CMOS is not suitable for low jitter applications.

The second photograph was taken much later and is the same output being used to test my 100MHz 2232.  The displayed aberrations are typical and produced completely within the oscilloscope and within the specifications although I think the performance could be improved slightly.

[Keysight DanielBogdanoff]

So, not infinite bandwidth but...

how about 3.5 ps edge @ 113 GHz realtime bandwidth? 

[TheSteve]

So, not infinite bandwidth but...

how about 3.5 ps edge @ 113 GHz realtime bandwidth? 

Show off! 

[_Wim_]

So, not infinite bandwidth but...

how about 3.5 ps edge @ 113 GHz realtime bandwidth? 

Is that a "hacked" DSOX1102, or do we need to buy something better for that?   

[HighVoltage]

So, not infinite bandwidth but...

how about 3.5 ps edge @ 113 GHz realtime bandwidth? 

WOW!
That would be a scope for Wave 2019!

What pulse generator are you using for this?

[JPortici]

Can't see the edge. I dare you to expand the timebase to 10ps/div

[Keysight DanielBogdanoff]

WOW!
That would be a scope for Wave 2019!

What pulse generator are you using for this?

It's our calibration pulse, so essentially the fastest edge we can muster. It's a laser - it turns out optical is much easier at these frequencies.

[bson]

It's our calibration pulse, so essentially the fastest edge we can muster. It's a laser - it turns out optical is much easier at these frequencies.

That's pretty incredible! 

Are there complete optical front ends for the UXR series?

[tggzzz]

WOW!
That would be a scope for Wave 2019!

What pulse generator are you using for this?

It's our calibration pulse, so essentially the fastest edge we can muster. It's a laser - it turns out optical is much easier at these frequencies.

Well, 110GHz is within a factor of 3 of being out of RF bands and into the IR bands!

[David Hess]

NIST used what was effectively an optically driven sampling oscilloscope as their reference for calibrating pulse generators and I assume they still have it.  I always assumed HP/Agilent/Keysite had something similar to use in-house.  I think Tektronix sent their pulse reference to NIST for calibration.

At lower frequencies, low being up to 10s of GHz, it is possible to use 3 sampling heads to calibrate each other without any outside reference by measuring their kick-out pulses which are otherwise just annoying during normal use.

[Electro Fan]

So, not infinite bandwidth but...

how about 3.5 ps edge @ 113 GHz realtime bandwidth? 

Wow - very cool and Thanks/Congrats to Daniel and Keysight for sharing!

I think that beats the previous best posted around here by over 10 ps.  We are now within less than 4 ps of seeing our first sub-picosecond rise time.  Maybe Keysight or someone has something laying around that can do that.....

Actually, we might only be about 2.5 ps away as under 1 ps would maybe qualify as sub PS?

[Electro Fan]

Probably should go for the extra ~3.5 ps and get firmly into the realm of 3 digit femto seconds.

[Wolfgang]

So, not infinite bandwidth but...

how about 3.5 ps edge @ 113 GHz realtime bandwidth? 

Ahem. Can we see this with a usable horizontal scale ?

[TheSteve]

I can't beat Daniel but am still pleased.

[JohnG]

Ok, so it's not the fastest, but it's pretty fast. It's also driving 5V into a 50 ohm load.

Texas Instruments LMG1020 gate driver in BGA package driving 50 ohms, measured with a Tek DPO7354C. Room for improvement on connection to SMA, but not bad. The chip has separate pull-up and pull-down outputs, and the resistors connecting the chip outputs to the transmission line are 1 ohm resistors in 0402 packages.

Cheers,
John

[Alfons]

Here is a screenshot of a signal from an ADF4351. I've gotten that part in order to better calibrate the MCP CRT of a 2467B in high frequencies. When programming with the arduino and testing, I was amazed to see that the part has quite fast rise times. Or do I understand something wrong, does the device measure wrong?

[Alfons]

I have just converted the TDS744a in a TDS784a, which was done without problems. The bandwidth has doubled. Here is a picture of the same signal as yesterday. You can see how a narrow bandwidth smoothes the signal.

[guenthert]

I have just converted the TDS744a in a TDS784a, which was done without problems. The bandwidth has doubled. Here is a picture of the same signal as yesterday. You can see how a narrow bandwidth smoothes the signal.

  While fundamentally one can expect a signal sampled with higher sample rate to produce a trace which better reflects said signal, in the examples given, there are enough sample points using the lower sample rate to show those 'humps' (harmonics) seen in the second trace.  I rather think those are two different signals.  Perhaps insufficient grounding in one?

  Ah, strike that.  Somehow I read 'bandwidth' you wrote as 'sample rate' (I'm having my coffee now).  If indeed the bandwidth of the low pass filter on the input got risen, you'd expect the different traces you got.  Don't mind me then.

[AVGresponding]

Sorry, couldn't resist   

[0culus]

I have just converted the TDS744a in a TDS784a, which was done without problems. The bandwidth has doubled. Here is a picture of the same signal as yesterday. You can see how a narrow bandwidth smoothes the signal.

I have an ADF4351 based signal generator evaluation board, and it looks fairly similar to that on my 7104. Really fast edges (I beat it by constructing a Jim Williams pulse generator though) but generally very ugly even with proper termination. 

[Alfons]

I have just converted the TDS744a in a TDS784a, which was done without problems. The bandwidth has doubled. Here is a picture of the same signal as yesterday. You can see how a narrow bandwidth smoothes the signal.

I have an ADF4351 based signal generator evaluation board, and it looks fairly similar to that on my 7104. Really fast edges (I beat it by constructing a Jim Williams pulse generator though) but generally very ugly even with proper termination. 

It would be overkill for me to get me a generator that produces clean signals to about 1 Ghz. But you can use that to test equipment. That's how I got the part. With a little skill you can use it to repair and calibrate equipment, because after all, the frequency is relatively stable to 1 Ghz and the frequency is also relatively accurate. Otherwise, I would not know what to do with it, because RF is not my area.

[0culus]

I originally bought the board because I needed a just over 3 GHz CW source that was juuust beyond what my 8664A could provide. I now have an 8672A 2-18 GHz signal generator, which obviously completely outperforms the eval board in virtually every relevant spec, especially phase noise.

[tautech]

Square waves from SDG6022X (80 MHz max) and SDG2042X (25 MHz max)
Taken with SDS5104X, Siglent 1 GHz rated BNC cable and feedthrough 50 ohm for the SDG2042X 10V p-p screenshot. All other shots using scopes inbuilt 50 ohm input.

[Mechatrommer]

few months ago verification... Rigol DS1054Z...





old Lecroy SDA6000...

[Electro Fan]

few months ago verification... Rigol DS1054Z...





old Lecroy SDA6000...

That looks like a very fast Rigol 1054Z

[Mechatrommer]

That looks like a very fast Rigol 1054Z

thats look like it but i dont know, thats what it said... i'm also a bit surprised... (tested with Leo Bodnar 30-40ps pulser) iirc that shape only happened on that V/div setting. if i increase (or decrease, dont really remember) when the relay clicked, that shape will be screwed... so i'm not sure whats going on inside there.

this is from another source tested much earlier (Uni-T UTG962 AWG Synch output)..

[Electro Fan]

That looks like a very fast Rigol 1054Z

thats look like it but i dont know, thats what it said... i'm also a bit surprised... (tested with Leo Bodnar 30-40ps pulser) iirc that shape only happened on that V/div setting. if i increase (or decrease, dont really remember) when the relay clicked, that shape will be screwed... so i'm not sure whats going on inside there.

this is from another source tested much earlier (Uni-T UTG962 AWG Synch output)..

Your measurements look like the Rise Time measurements but I can't quite figure it out.

As a frame of reference attached are a couple measurements made with Leo Bodnar's pulser; the LB pulser is spec'd for 30ps but I don't see how that can be achieved unless a scope can keep up.

The first two attachments show a Rigol 2072 spec'd for 70 MHz but that probably achieves a bit over 100 MHz - maybe at -3dB given the measured rise time of about 3.3 ns, and a Tektronix 2467B spec'd for 400 MHz which would imply a 875 ps rise time but that is measured at about 824 ps which implies a bandwidth of about 425 MHz.

In the attached chart are calcs for the 2072, the 2467B, and the 1054Z; these show that your 700 ps RT equates to a 500 MHz bandwidth and your 500 ps RT equates to a 700 MHz bandwidth.

Attached is an old spec sheet that shows some published numbers for a Tektronix 2465 and 2465A and my calculations (using the standard .35 formula) seem to arrive at similar numbers as a sanity check....
https://www.testequipmentdepot.com/usedequipment/tektronix/oscilloscopes/2465series.htm#:~:text=Increase%20in%20bandwidth%20from%20300,delay%20measurements%20(with%20CTT%20Option)

...but it's getting late here so I'm thinking maybe I've made some calc errors; however, if my numbers add up and yours are correct, I think you might have the fastest 1054Z known to mankind.

[Fungus]

That looks like a very fast Rigol 1054Z

thats look like it but i dont know, thats what it said... i'm also a bit surprised...

Plenty of people have seen similar results with the right cables, termination, etc.

(it's buried somewhere in the massive Rigol thread....)

[Electro Fan]

After looking at your Rigol posts and my Rigol while playing with the cursors, I think there is an error in the way we are I am using/interpreting the cursor measurements. 

I think your AX numbers of -800 and -500 ps are the distance to the left of the trigger line, and your BX numbers of 700 ps and 1.3 ns are the distances to the right of the trigger line. 

Try using the built-in Rigol Rise Time measurement and see if you get a number that is different than what your AX and BX cursor measurements are displaying. 

The BX-AX is more likely the Rise Time.

I got mesmerized by looking at ps measurements; I'm guessing what the Rigol cursor measurements are trying to tell us is that the Rise Time is 1.5 ns to 1.8 ns which would imply about 233 MHz to 190 MHz - still very fast for a 1054Z but somewhat more plausible.

Try the Rigol built-in Rise Time measurement and let us know.  My bad for even raising the issue.  Sorry. 

[Electro Fan]

Attached is a file showing the 2072 Rise Time of 3.3 ns.

Note that the B->X = 2.000ns display just happens to be highlighted because the cursor menu selection was set to SelectCursor X and CursorB.  So your eye is drawn to what is highlighted; makes sense except that if what you are really looking for is DeltaX (what I think is the Rise Time), then you might be (in my case, at least) temporarily confused.   

On the 2072 Rigol uses the convention DeltaX and on the 1054Z Rigol uses the BX-AX convention.  These are nitty little things but either way until you are fully indoctrinated (or at least paying attention, duh), it's possible to misinterpret a displayed value.  All good lessons that I'm happy to have learned.    

And, I'm still leaving open the possibility that I'm still missing something.....  so feel free to point it out.... I heard someone say recently we learn much more from our mistakes than when we get it right.  I'm feeling like I'm continuously in the deep end of the learning pool. 

Slightly veering off topic but I just noticed... doesn't seem like the Rigol 2072 display shows the 10% and 90% markers that would be nice to have for RT measurements.

[T3sl4co1l]

Not having seen the settings, acquisition and all that -- it could easily just be a glitch, with sinc interpolation making it look believable.  (The suspiciously small number of points seems to hint at that?)

I can do the same thing, to literally unbelievable risetimes, on my TDS460 -- this being relatively easy as it uses equivalent time sampling.  (Heh, though I don't know how I'd trick it to acquire a nice step; it's random sampling I believe, it just assembles a waveform bit by bit.)

Heh, and at maximum settings (1ns/div sweep, 50x zoom), it can show all the way down to 20ps/div.  Not that anything it can properly acquire is at all meaningful there (it's only 350MHz BW).

Tim

[graybeard]

This is the output of my 1GHz Colby PG100A pulse generator running at 200 MHz into my 1GHz Tektronix TDS784D.  The Colby (with GaAs drive option) is rated for a rise and fall time of <250ps, so the times shown are a limitation of the scope.











Click on the images above for a larger version.

Chris

[Electro Fan]

Not having seen the settings, acquisition and all that -- it could easily just be a glitch, with sinc interpolation making it look believable.  (The suspiciously small number of points seems to hint at that?)

I can do the same thing, to literally unbelievable risetimes, on my TDS460 -- this being relatively easy as it uses equivalent time sampling.  (Heh, though I don't know how I'd trick it to acquire a nice step; it's random sampling I believe, it just assembles a waveform bit by bit.)

Heh, and at maximum settings (1ns/div sweep, 50x zoom), it can show all the way down to 20ps/div.  Not that anything it can properly acquire is at all meaningful there (it's only 350MHz BW).

Tim

With all due respect, I don't believe we were looking at a "glitch".  It was just a mis-read/misinterpretation of the the cursor readout values.


Edit:  added some photos... original at 700 Pts (what the Rigol chose on Auto) and same waveform from same pulse gen showing same cursor display values at 1.4 MPts, 14 Mpts, and 56 Mpts.  The whole discussion of why Mechatrommer's 1054Z seemed so blindingly fast was because I got us off track when I saw numbers like 700 ps and 500 ps*; it was just me looking at the displayed values (values that at first I thought were Rise Times but I'm now pretty sure are just the deltas to the trigger line).  So these values weren't intended to be interpreted as Rise Time values, that was just my error.  It certainly wasn't anything Mechatrommer did or misinterpreted; he just posted his results.  His posts were A-OK/perfecto and I think his 1054Z is A-OK/normal, ie, very fast for a 1054Z but not fundamentally different than other 1054Zs we've seen.

*I can't help it, I get excited when I see anything with picoseconds 

[Mechatrommer]

if my numbers add up and yours are correct, I think you might have the fastest 1054Z known to mankind.

i think mine is just normal like everybody else rigloled to 100MHz, i suggest someone try the setting, 500mV/div, sinc(always on cant turned off of course), peak acq.. reducing to 200mV/div signal will be distorted similar to your shown 2072 signal.. i smelled ifft effect since there's slightly gibbs phenomenon visible on my signal, i was just enjoying the squareness of it without giving much thought on RT figure. I did check with my erasynth micro last night after you brought this up, the -3db signal bw of my 1054z is just about 270MHz... so no magic there.. i forgot ds1054z has a risetime meas built in, i'll try that later if i remember, now in office and lack of sleep.

[Electro Fan]

Not having seen the settings, acquisition and all that -- it could easily just be a glitch, with sinc interpolation making it look believable.  (The suspiciously small number of points seems to hint at that?)

I can do the same thing, to literally unbelievable risetimes, on my TDS460 -- this being relatively easy as it uses equivalent time sampling.  (Heh, though I don't know how I'd trick it to acquire a nice step; it's random sampling I believe, it just assembles a waveform bit by bit.)

Heh, and at maximum settings (1ns/div sweep, 50x zoom), it can show all the way down to 20ps/div.  Not that anything it can properly acquire is at all meaningful there (it's only 350MHz BW).

Tim

With all due respect, I don't believe we were looking at a "glitch".  It was just a mis-read/misinterpretation by me/EF of the the cursor readout values.
edited to clarify it was my error

i was using manual cursor and calculation to get 10 and 90% level, and criss cross intersect the vertical cursors to get risetime. As said i forgot there is built in risetime math i'll try that later...

- just to confirm, this was my (Electro Fan's) error caused by my mis-read on the values displayed, it was not a mis-read or any error by Mechatrommer

[Electro Fan]

While it's good to learn from the misses, when shooting free throws it's good to end on a made free throw.  So just to show we know a rise time when we see a rise time, here is one that's pretty close to 30 ps.

[Fungus]

if my numbers add up and yours are correct, I think you might have the fastest 1054Z known to mankind.

i think mine is just normal like everybody else rigloled to 100MHz

Turbo Tom did it and got the image below. Original post here

[Mechatrommer]

- just to confirm, this was my (Electro Fan's) error caused by my mis-read on the values displayed, it was not a mis-read or any error by Mechatrommer

retested again with Leo Bodnar Pulser and built-in rT math on CH2 (no cable, direct connection from pulser to inline (diy) terminator to scope. yup confirmed somewhere 1.3-1.8ns (|AX-BX| in manual cursor). so the BW is 200+ MHz. one youtuber confirmed this as well (using -3dB FG amplitude observation) and as Fungus said, many others did too, so i'm normal but when you decrease V/div to 200mV/div (in 1X attenuation setting), relay clicked and boom, 2.6ns and bad risetime (3rd pic) about similar looking to your 2072 picture @ 10mV/div

[Fungus]

when you decrease V/div to 200mV/div (in 1X attenuation setting), relay clicked and boom, 2.6ns and bad risetime (3rd pic) about similar looking to your 2072 picture @ 10mV/div

1x probes have more capacitance.

[rf-loop]

when you decrease V/div to 200mV/div (in 1X attenuation setting), relay clicked and boom, 2.6ns and bad risetime (3rd pic) about similar looking to your 2072 picture @ 10mV/div

1x probes have more capacitance.

  First write and after then think... good practice, is it.  (even when your sentence is right itself but in context and with images you answer just

[Mechatrommer]

when you decrease V/div to 200mV/div (in 1X attenuation setting), relay clicked and boom, 2.6ns and bad risetime (3rd pic) about similar looking to your 2072 picture @ 10mV/div

1x probes have more capacitance.

your statement is not wrong, but i guess in this case, it has nothing to do with attenuation setting in FW (FW just multiple the signal accordingly) nor a 1x coax cable. i was using the same 50 ohm termination setup (no cable), i only rotated the V/div knob (500mV/div to 200mV/div in 1X setting ie 5V/div to 2V/div in 10X setting), relay clicked and the displayed signal changed, same input signal setup, no change. i highly believe its the signal paths difference inside the oscilloscope.

[David Hess]

but when you decrease V/div to 200mV/div (in 1X attenuation setting), relay clicked and boom, 2.6ns and bad risetime (3rd pic) about similar looking to your 2072 picture @ 10mV/div

Look very carefully at the area from 1 to 3 nanoseconds after the trigger in your last image; the shape of the pulse edge changed!  And it became very straight which indicates overload or cutoff of an amplifier stage due to excessive slew rate, so the full power bandwidth is not sufficient to support 100 MHz operation.  The full power bandwidth matters because at 200mV/div, the relay click you noticed removes the high impedance input attenuator and applies an order of magnitude more signal to the input stages.

Older 100 MHz oscilloscopes with *faster* transistors maintained an order of magnitude less signal at the input stage by including more input attenuators to control signal levels and not surprisingly, delivered consistent performance at all input attenuator settings.

[Fungus]

1x probes have more capacitance.

your statement is not wrong, but i guess in this case, it has nothing to do with attenuation setting in FW (FW just multiple the signal accordingly) nor a 1x coax cable. i was using the same 50 ohm termination setup (no cable),

Oh, duh, you're using a cable not a probe...   

It was a knee jerk reaction to "I get different results in 1x mode then 10x mode".

i only rotated the V/div knob (500mV/div to 200mV/div in 1X setting ie 5V/div to 2V/div in 10X setting), relay clicked and the displayed signal changed, same input signal setup, no change. i highly believe its the signal paths difference inside the oscilloscope.

Makes sense.

[tautech]

Leo Bodnar 10 MHz pulse generator.
http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295
Supplied test sheet = sub 30ps rise and fall times.

2 GHz BW SDS6204A

[mawyatt]

Nice, those look great!!

Any chance you could show the 10 bit and various ERES modes with this new scope?

Best,

[tautech]

Nice, those look great!!

Any chance you could show the 10 bit and various ERES modes with this new scope?

No 10 bit mode in this one Mike but study the screenshots in the SDS6000A thread.  This thing has some nice tricks.
Not played much with ERES yet but will post something when time allows in the 6kA thread.

[JohnG]

Those transition times (~250 ps) seem rather long for a 2 GHz bandwidth scope. I saw that the spec is 230 ps, but the 1 GHz version of the scope is 350 ps. Whatever they are doing to get the extra bandwidth is not helping the risetime nearly as much.

John

[tautech]

Those transition times (~250 ps) seem rather long for a 2 GHz bandwidth scope. I saw that the spec is 230 ps, but the 1 GHz version of the scope is 350 ps. Whatever they are doing to get the extra bandwidth is not helping the risetime nearly as much.

John

See here for for an example with a 1 GHz model:
https://www.eevblog.com/forum/testgear/siglent-sds6000-pro-10-and-12-bit-dso-coming/msg3876329/#msg3876329

[David Hess]

Those transition times (~250 ps) seem rather long for a 2 GHz bandwidth scope. I saw that the spec is 230 ps, but the 1 GHz version of the scope is 350 ps. Whatever they are doing to get the extra bandwidth is not helping the risetime nearly as much.

Higher bandwidth oscilloscopes often lack a Gaussian or simple transition band response so they do not follow the 0.35 relationship between rise time and bandwidth.

[rf-loop]

Those transition times (~250 ps) seem rather long for a 2 GHz bandwidth scope. I saw that the spec is 230 ps, but the 1 GHz version of the scope is 350 ps. Whatever they are doing to get the extra bandwidth is not helping the risetime nearly as much.

Higher bandwidth oscilloscopes often lack a Gaussian or simple transition band response so they do not follow the 0.35 relationship between rise time and bandwidth.

Exactly. And just this is case here and based to hard facts. Rejecting aliasing is much more important than this rise time. We have here maximum sampling frequency 5GHz, so fNyquist is 2.5GHz.   If with this sampling frequency we want BW 2GHz (and this mean allways pure sinewave) there is really small room before Sinc reconstructions start problems and also only 0.5GHz to Nyquist.  If there is some kind of "Gauss" type analog BW before ADC it may aliase lot with fast edges. We need cut these harmonics what reduce edges time. 
Band width MHz is 350/risetime (ns) is really only old and bit "simply" thumb rule. It was somehow ok thumb rule in old analog oscilloscopes times tens of years ago. Now need think lot of more. In old times with discrete components made oscilloscope typically have gaussian type BW shape from input to tube cathode ray Y deflection. Today we need care aliasing, least with serious instruments.

No one can make real analog brick wall filter but theoretically we can still think it. Think about its risetime and frequency -3dB  corner.
Usually "flat top" type BW (also some times called as "brick wall" type) in higher freq oscilloscopes may have this "thumb rule" number not 350 but 400... 450 and even more, depending how steep BW rejecting filter is and and other features of this LP filter (what is always compromise between many things).
Only way to measure oscilloscope BW is sinewave generator and signal level controlled for oscilloscope input, not generator output alone - if accuracy is important.
Oscilloscope risetime can measure using known fast edge what ends to known real flat top without overshoot.

This is a good example of how some and many peoples imagine that measuring the rise time can calculate the BW of an oscilloscope. It is for the most part a misunderstanding when understanding is poor and applied incorrectly. It’s an old and partly outdated rule of thumb that, however, is spreading everywhere on the internet as if it were some sort of de facto. Yes it is an ok rule of thumb for a 60 year old Tektronix oscilloscope. It was just okay when Tek published this rule of thumb in history. We have to walk out of that religion.

Here some bottom basics what everyone need know and also understand. https://www.keysight.com/zz/en/assets/7018-01129/application-notes/5988-8008.pdf

[JohnG]

I'm well aware that the tr*BW=0.35 is a simple rule of thumb that is generally only valid for single-pole analog filters. What I found interesting is that the scope series specs show 350 ps for 1 GHz and 230 ps for 2 GHz, and yes, this is likely due to the fact that the sample rate doesn't change and you are operating close to the Nyquist limit. However, I was surprised at just how big the penalty is, and I thought it was worth pointing out.

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

[2N3055]

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

Could you please explain where do you get this 400ps from?

[tautech]

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

Could you please explain where do you get this 400ps from?

1 GHz models. 

[JohnG]

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

Could you please explain where do you get this 400ps from?

1 GHz models. 

Yes, thank you. I followed the link you provided and then looked up the specs for both models of the scope. I should have made this more explicit.

I am only nitpicking about the risetime because this is an important spec for my job (and for this thread). Anyone evaluating a scope has to balance their needs, budget, and the feature set of the scope, but I think there might be at least one thread about that already .

John

[RAPo]

Square wave from an HP 3300A, a rise time of 287.87ns.

[tautech]

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

Could you please explain where do you get this 400ps from?

1 GHz models. 

Yes, thank you. I followed the link you provided and then looked up the specs for both models of the scope. I should have made this more explicit.

It need be made clear the slower risetime screenshot was from a 1 GHz enhanced SDS5054X not this new 2 GHz SDS6204A and therefore is not even a true representation of SDS6104A risetime performance.

I am only nitpicking about the risetime because this is an important spec for my job (and for this thread). Anyone evaluating a scope has to balance their needs, budget, and the feature set of the scope, but I think there might be at least one thread about that already .

Sure. 
Yet we must look at the full picture of the stated risetimes of Leo's pulsers measured with SD30 sampling heads that are specified to 40 GHz and some members here have earlier versions of Leo's pulsers that are slower 40-50ps versions.
Still looking at these fast edges can only be as reference/comparisons with scopes of the BW's of the last few posts.

[2N3055]

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

Could you please explain where do you get this 400ps from?

1 GHz models. 

There are two basic hardware variants of SDS6000. 
One has 2 ADC and maxes out at 1 GHz. It comes in 10/12 bit and is China only. That one will have 400 something ps risetime, similar to SD5104X.

Other one is 2 GHz capable platform with 4 ADC. That one is available in 10/12 bit in China only, and in 8 bit global release. Being 2 GHz capable and sampling at 5GSs/s on all channels, when run at 1 GHz it will have 350 ps risetime.

[rf-loop]

I also think it is worth pointing out that the measured data shows something closer to 400 ps and 250 ps respectively, meaning the measured risetime is more than 10% higher than the spec in both cases. One could argue that 10% is not that bad, but my prior experience has been that if proper care is taken, most scopes I have used have met or exceeded this spec.

I am curious if this is an artifact of how the scope calculates risetime, a setup problem (e.g. a thin cable), or something else. It would be informative to see the edge on a shorter timescale, say 0.5 ns/div, with cursors showing the 10% and 90% points. Then one might get a better idea of what is happening.

John

Could you please explain where do you get this 400ps from?

1 GHz models. 

There are two basic hardware variants of SDS6000. 
One has 2 ADC and maxes out at 1 GHz. It comes in 10/12 bit and is China only. That one will have 400 something ps risetime, similar to SD5104X.

Other one is 2 GHz capable platform with 4 ADC. That one is available in 10/12 bit in China only, and in 8 bit global release. Being 2 GHz capable and sampling at 5GSs/s on all channels, when run at 1 GHz it will have 350 ps risetime.

China domestic only SDS6000 H10 Pro and H12 Pro  350MHz, 500MHz and  1GHz models have datasheet risetimes 1ns, 700ps and 450ps.
These models are different and only available in China.  As @2N3055 told different platform including also fact that 2 ADC.
In these models ADC fNyquist is 1.25GHz when more than 1 channel is in use in either channel pair.

China domestic only SDS6204 H10 Pro and H12 Pro  2GHz. It have datasheet risetime 230ps. This model have separate ADC for every channel.
In this model ADC fNyquist is 2.5GHz independent of number of channels in use simultaneously.


Outside China models SDS6000A are 4 ADC models like this China domestic 2GHz model. These all Outside China models are all 8 bits without known exception.

These models are SDS6054A, 6104A and 6204A. These all are based to this 4 ADC platform as is also China domestic 2GHz model only.
These 4 ADC  500MHz, 1GHz and 2GHz models datasheet risetimes are 550ps, 350ps and 230ps.
In these all models ADC fNyquist is 2.5GHz independent of number of channels in use simultaneously.

As can be seen looking these bolded times, risetimes are not based on the 350 / BW “rule of thumb” because the BW shape is not Gaussian for compelling reasons,  if one realize that this is not an entry-level hobby model.
They are just hobbyists / noobes who think the best hacking is to get more BW. Many times it is not. Without full exclusion that  in some cases it may give more without high adverse effects.
For many entry-level scopes, the best hacking is to discard an over-wide BW, relative to the sampling frequency, and this must be done inside the hardware before the ADC. I have not seen these wise and not so easy modifications  here in forum at all.

[Martin72]

Show us your squarewave, today a lecroy WR9054 (500Mhz, 20GSa/s), Bodnar 10Mhz 40ps.

[Martin72]

Same, but with my sds2k+...

[tautech]

Same, but with my sds2k+...

Any different in 10 bit mode ?

[Performa01]

Same, but with my sds2k+...

Any different in 10 bit mode ?

We would expect even a huge difference! Something more like 3 ns rise time istead of <700 ps.

[Martin72]

Yep, just did it a few minutes ago...

[jasonRF]

Now for something on the lower-performing side.  This measurement is from a Picoscope 2204a (100 MS/s, nominal 10 MHz BW and 35 ns rise time) using the probes that were included with it; they are x1/x10 switchable with respective specified bandwidths of 15 MHz/60MHz.  A NanoVNA was used for the source - I have no idea how clean the square waves are out of this cheap device but it goes up to 1.5 GHz so it must have much shorter rise/fall times than the Picoscope (EDIT: just to be clear, the nanoVNA only produces square waves up to 300 MHz; it uses the 5th harmonics to perform measurements the 900-1500 MHz range). 

Hookup: nanovna 50 Ohm SMA output -> SMA to BNC adapter -> BNC to alligator cable (~1 meter) clipped across 50-Ohm resistor -> scope probe across resistor.   This is admittedly a little flaky.  Without the scope probe across the resistor, the nanoVNA measured a return loss of -30 dB at 1 MHz, -20 dB at 7.7 MHz, and -11.5 dB at 25 MHz (the highest I bothered to measure).  Not so great at the higher end.

Anyway, the first image is with probe switched to x10, giving 12 ns rise and 13 ns fall.  The second image is with probe at x1, yielding about 14 ns rise and fall, and some additional overshoot and ringing.  Note the sampling time is 10 ns, so this is all the sinc interpolation at work.  I'm not sure how much uncertainty this adds.  Even if the rise time is 20 ns the Picoscope is better than I thought it was.   

[THDplusN_bad]

Good Day,

Ok, I realize that this is an old thread, but still an interesting topic

I was hooked up by the simplicity of the 74AC14-based fast rise pulse generator design. So, same as many other members I have built my own earlier this week. Nice!
I have used a simple double-sided copper board from the scrap pile and the results of this simple thing built in "dead-bug style" are pleasing.
I have just added a "proper" power connector, a diode to protect from reverse supply voltages and some stand-offs. Used a 100 nF cap. and a 10k resistor SMDs for the oscillator, as these 0805 size components fit nicely.
The BNC output connected is mounted on an old Tektronix assembly mount, which is a left over from an older oscilloscope repair. 
Voilá - the simple thing worked right from the start and creates a nice 960 Hz square wave with an amplitude of about 3.4Vpp into 50 Ohms.

I have measured rise times between 1.8 ns and 2.1 ns (10% to 90%) per the attached screenshots. These were taken with an entry-level LeCroy Type Wavejet 334 DSO, which is spec'd at 1 ns typ rise time and 350 MHz BW.
The output signal overshoots by around 29%, but that's fine and the distinct peak makes it even useful when one uses it as a poor man's TDR.
And I had much fun when I was following Alan's (W2AEW) excellent video "#88: Cheap and simple TDR using an oscilloscope and 74AC14 Schmitt Trigger Inverter"
I was amazed to find out that this method allowed me some correct cable length measurements of two cables (an Aircell-5 and a plain-vanilla RG-58 made by HP) down to centimeter accuracy. Nice work, as always, Alan... @w2aew ! 

Cheers,

THDplusN_bad

[joeqsmith]

You may find the following of interest as well where we look at several types of gates ran over various temperatures and voltages.     

https://www.eevblog.com/forum/projects/waveforms-in-a-74ls04-ring-oscillator/

[PartialDischarge]

Somewhere in a thread user ttggzz suggested the use of LVC gates in parallel, I made a board to test the idea and I'm getting less than 500ps rise and fall times with very nice shape, tested with a 1GHz scope:

[tggzzz]

Somewhere in a thread user ttggzz suggested the use of LVC gates in parallel, I made a board to test the idea and I'm getting less than 500ps rise and fall times with very nice shape, tested with a 1GHz scope:

Here perhaps: https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg1902941/#msg1902941


Good to see the results can be replicated. It looks like the scopes I was using (not mine, very fast test) used the 20%-80% times, which would be faster than the 10%-90% times.

I used 143ohms in series since the gate output is ~7ohms. I don't think that would make too much difference in practice - decoupling would make more difference.

[PartialDischarge]

I tried with a 74VHC gate but it is slower, I'm very happy with the results since 2.5V 500ps is very useful for many applications, it is a fairly cheap solution and aberrations are minimal which I consider important

[tggzzz]

I tried with a 74VHC gate but it is slower, I'm very happy with the results since 2.5V 500ps is very useful for many applications, it is a fairly cheap solution and aberrations are minimal which I consider important

Agreed.

You can also reduce the output swing by reducing the PSU voltage, but the transition time increases. Try reducing Vcc  to 1V or so, and seeing if you get a 0.5V swing with 3ns risetime (and some "pre-undershoot" for want of a better term). You can go even lower, with some entertaining[1] aberrations The aberrations are gone by 1.7V or so, as expected.

[1] I'm easily entertained

[tchiwam]

4 outputs on top of each other

100us pulse 1 PPS rising edge ~3GHz BW

[tggzzz]

4 outputs on top of each other

100us pulse 1 PPS rising edge ~3GHz BW

4 outputs of what?

Why not use averaging?

PPS? And those figures don't seem to match the figures in the photograph.

[tchiwam]

I was comparing 4 of the 8 putputs from my PPS distribution. That's s the rising edge of a 100us pulse.

The measurements on the side are out of the window so they are wonky except for the cursors.

[bozidarms]

on CSA830A, my new toy   - 20,8ps -  rise and fall time!

[HighVoltage]

@bozidarms

20.8 ps rise and fall times ?

What generator do you use for that?
And what scope and probe?

[bozidarms]

It`s one Tektronix CSA803A with SD-24 TDR/sampling head.
However, that is my 3. SD-24, which has characteristics far more better than proclamated.
The other two wasn't so god.

That is a test pulse from SD-24 itself on SMA out, which is only shorted.
Measurement is at 10% - 90%.

[Aldo22]

- kind of curious to see what is the lowest price device is that can produce a really good looking square wave at 1, 5, 10, 20, and 30 MHz?

I don't know if "really good looking" but it's very low priced. 
The signal comes from a ESP32 microcontroller  for ~ 5$.
The oscilloscope is a handheld ZEEWEII DSO2512G for ~ 80$.

Please note:
The 40MHz measurement was made in the overclocking mode of the device (Menu Aux + ⇧ [long])
with 250MHz probes and a ground spring.

[the Chris]

My pulse generator from Leo Bodnar arrived yesterday, so I would like to contribute with my slow-but-I-am-loving-it EDUX1052A. Measurements were taken with an RS Pro 50Ohm inline terminator that I ordered from Leo alongside the pulser.

I got 5.8767ns over 112k measurements. Considering the specified 50MHz and therefore assuming a classic -3dB drop, the BW = 0.35 / r_t should be valid, resulting in 60MHz bandwidth.

This is in line with what I estimated using a 10MHz to 60Mhz sinus sweep of my UTG962E, with pretty much no drop under 10MHz (not shown) and about ~1.2V peak in amplitude at 60MHz using a N2142A 75MHz probe in 10x mode.

Thanks Leo for the fast shipping and now including the customs and taxes loads for EU members!

EDIT: 5ns/div measurement added

[David Hess]

My pulse generator from Leo Bodnar arrived yesterday, so I would like to contribute with my slow-but-I-am-loving-it EDUX1052A. Measurements were taken with an RS Pro 50Ohm inline terminator that I ordered from Leo alongside the pulser.

I got 5.8767ns over 112k measurements. Considering the specified 50MHz and therefore assuming a classic -3dB drop, the BW = 0.35 / r_t should be valid, resulting in 60MHz bandwidth.

I wonder where that aberration came from; it is much greater than I would expect considering the much faster settling time of the pulse generator compared to a 60 MHz oscilloscope.

My guess is that the oscilloscope does *not* have a Gaussian or single pole response.

[Sighound36]

Below are four examples of square wave forms I looked at earlier, one using the Siglent SDG2042A 10Mhz 4V pk<>pk / 10Mhz ultra low phase noise -124dbm@1hz to -175dbm@10Mhz/ Leo Bodnar 40pS rise time generator/ 44.1Khz word clock.

Using Wavepro 4Ghz HD scope 50 Ohm T-flex 405 18Ghz cabling, full scope BW of 4Ghz NO ERS (software enhancement) up to 20GS/s rate. Scope up to temprature and calibrated.

[Sighound36]

As we can only post 10 attachments second post last of the 44.1Khz images plus I thought if would be nice to show the eye pattern for each of these square wave sources as well

[joeqsmith]

I followed  Leo Bodnar's threads about that pulsar but never bought one.   All of my scopes are too slow to verify it. 

Many years ago, I stumbled onto an employee of LeCroy who had purchased some of their junk at an internal auction.  They had the test fixtures for the 7200A.  Another gem was they had some of the 7262 plugins.  These are the only ones I have ever seen.   This plugin includes an ECL output for TDR measurements and has an analog BW of 4GHz.   I posted some data for it recently where it measures 118ps.   

https://www.eevblog.com/forum/testgear/12-ghz-active-probe-project/msg5007958/#msg5007958

I posted about my conversations with LeCroy about the risetime and bandwidth:
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg593071/#msg593071

Typically RT*BW = 0.40 to 0.45 for modern high bandwidth scopes

4GHz * 118ps = 0.472.   Much higher than 0.35.   

If I attach another old relic, Tektronix S-52 which has a risetime of less than 25ps, the scope measures 111ps.   Or 0.444. 

This scope was my first DSO, outside of my HP scope/logic analyzer.   Originally owned by the USAF.   Released in 1989.   She's old but fun to play with.

[Grandchuck]

Here is a result from a Tektronix Scope Evaluation board and a Siglent DS2202.  The board has a 4-bit counter with a risetime of around 2 nsec with some overshoot.

[tggzzz]

Here is a result from a Tektronix Scope Evaluation board and a Siglent DS2202.  The board has a 4-bit counter with a risetime of around 2 nsec with some overshoot.

How was the probe's shield connected to the board's ground? A 6inch ground lead is a classic cause of overshoot.

[Grandchuck]

Your guess is close ... it is a 5 inch lead.  They put the ground pad as far from TP1 as possible???
I included a shot from the manual that came with the board.

[joeqsmith]

That's funny to even see one of these boards.   I picked up what appears to be the same one directly from Tektronix when I bought my first scope (Hitachi) back in the 80s.   I think they were giving these away back then as a promotion.   
 
Connecting from pin1 to pin4 using a LeCroy PP061 resistive probe with a pretty much dead battery,  scope measure 1.65ns without the big overshoot.  The BW is much higher than what you have available and there is no ringing.  I also suspect your connection from the board to the scope. 

[tggzzz]

Your guess is close ... it is a 5 inch lead.  They put the ground pad as far from TP1 as possible???
I included a shot from the manual that came with the board.

Have a look at https://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/

As a quick test I would wrap a length of wire around the probe body, with a short straight spike to the gnd hole on the left. In other words, a variant of the "spiked spring" supplied with the probe.

[joeqsmith]

Recently someone was asking about how to use a scope and signal generator to measure the self resonance frequency of an inductor.    I provided several examples, the later using a square wave to cause the inductor to ring at at the SRF.   

https://www.eevblog.com/forum/beginners/measuring-the-self-resonant-frequency-of-an-inductor/

As long as I have the pulser out... shown is a Mini-circuits 6.3 - 15GHz high pass.  Data sheet may be found at:
https://www.minicircuits.com/pdfs/VHF-6010+.pdf

I attached this to the old Tektronix pulser and then into my LeCroy 8500A.  This scope has a BW of 5GHz.  They claim a typical rise time of 90ps.   Obviously the filter is outside the limit of what the scope can measure.  Ignore that.  The signal was stable and I used RIS to get a clearer picture what is going on.   What I thought was interesting is it appears to have a dominant SRF of about 6.2GHz.

In the end, who smacks a filter like this anyway.... 

[Grandchuck]

tggzzz and Joe are great motivators.  Look and see what happens.
Now, why would Tektronix do that?  One would think that their pictured result would exemplify best practices???

[joeqsmith]

Now, why would Tektronix do that?  One would think that their pictured result would exemplify best practices???

Well ... Back in the 80's my mind set was a PC with a clock frequency of 50MHz, never going to happen.    I will never need a scope with more than 100MHz BW.  ....  Our high end scope where I worked was a large 100MHz Tektronix DSO.  I was using a Tektronix Polaroid camera to record data...   I'm not surprised at all by the demo boards layout.  Wouldn't surprise me to find out it was an intern's project.   

The trigger and missing pulse test was a problem for some of our scopes at that time.   

I keep a spook of wire on-hand to make these springs from scratch.  1) I start by tightly wrapping the probe's ground.  2) I remove the spring and give it a half turn.  Round need nose pliers work fine.  This gets enough tension on the spring to lock to the probe.   3) Ground strap is made from copper foil.  Sometimes I use braid.   All depends...  4) Solder the spring to the strap.  5) For insulation, I use Kapton.  With braid, some heat shrink or woven high temp fabric.   Depends.    6) Solder the ground strap to the board we leaded solder.  I won't use that lead free stuff for home use.    7) attach probe and measure.

Still not a great setup, but consider these are pretty slow edges we are dealing with.  Here was a home made probe where we were playing with much faster edges.   I was attempting to get the ground inductance and loop as small as possible.

https://www.eevblog.com/forum/testgear/12-ghz-active-probe-project/msg5006290/#msg5006290

[Gerhard_dk4xp]

<    https://kh6htv.com/pspl-app-notes/   >

Most interesting reading.  When the founder/owner of Pico Secod Puls Labs retired,
he sold the farm to Tek.
First thing that TEK did was to axe the app notes from the PSPL web site.
Probably too many independent comparisons.   

Gerhard

[joeqsmith]

<    https://kh6htv.com/pspl-app-notes/   >

Most interesting reading.  When the founder/owner of Pico Secod Puls Labs retired,
he sold the farm to Tek.
First thing that TEK did was to axe the app notes from the PSPL web site.
Probably too many independent comparisons.   

Gerhard

I took it that was his kid.   Seems most private companies don't survive once they are handed off to the next generation.  Normally the kids are not prepared and the company dies in short time.   I watched an interview with Soichiro Honda where one of the questions was who would be his successor.   He was very point blank about not letting his kids have it.  Too much of his life to build it.

Jim retired from PSPL in 2001 and turned over the reins of the company to his oldest son, Scott. PSPL was a dynamic, high-tech company producing ultra-fast risetime (5 ps) and ultra-high bit rate (40 GB/s) pulse and pattern generators and bit error rate detectors, 100GHz sampling oscilloscope, plus a line of ultra-broadband (kHz to > 50GHz) coaxial components, including amplifiers and bias tees.    In January, 2014, PSPL was sold to Tektronix.

[the Chris]

My pulse generator from Leo Bodnar arrived yesterday, so I would like to contribute with my slow-but-I-am-loving-it EDUX1052A. (...)

I wonder where that aberration came from; it is much greater than I would expect considering the much faster settling time of the pulse generator compared to a 60 MHz oscilloscope. My guess is that the oscilloscope does *not* have a Gaussian or single pole response.

Yes, I did not expect to see this kind of overshoot on a scope with 50MHz bandwidth. For reference, this is the same pulser on the EXR104 I am using at work. This time without inline terminator in native 50R mode.

[David Hess]

Yes, I did not expect to see this kind of overshoot on a scope with 50MHz bandwidth. For reference, this is the same pulser on the EXR104 I am using at work. This time without inline terminator in native 50R mode.

Now you get to ask yourself why there is preshoot.

[joeqsmith]

GigaWave with Tektronix S-52 tunnel diode head (<25ps Tr)

https://www.sjl-instruments.com/

[hpw]

GigaWave with Tektronix S-52 tunnel diode head (<25ps Tr)

https://www.sjl-instruments.com/

Nice, what I would like to see the real time behavior, as 20..80% or 10..90% rise time changes over time

On a LeCroy easy to graph over time as rise f(t).

[SJL-Instruments]

GigaWave with Tektronix S-52 tunnel diode head (<25ps Tr)

https://www.sjl-instruments.com/

Nice, what I would like to see the real time behavior, as 20..80% or 10..90% rise time changes over time

On a LeCroy easy to graph over time as rise f(t).

Thanks for the suggestion  We'll add the ability to graph any measurement vs. time to the software. (Fastest update rate would be 1 datapoint per sweep.)