Show us your square wave

[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