Rigol's "long memory"

[cyberfish]

I have decided to buy a DSO, and came down to Instek 1062A (seems like a very good deal), and Rigol 1052E (just because it can be hacked to 100mhz).

I'm leaning towards the Instek, because of the memory depth.

Then I saw on the Rigol DS1052E page that it has 1 Mpts "Long memory". What does that mean? Is it just marketing crap?

Also, are there other notable differences (except 60mhz/100mhz, and memory depth) between the 2 scopes?

Google doesn't seem to know anything about it, and the Rigol site requires registration to download the manual (what? really?).

Thanks

[alm]

I don't have the Rigol scope, so I'm not the best person to answer this, but I believe the Rigol has a special 'Long memory' mode to be able to use the 1Mpts, otherwise, you can only use 10kpoints or so. The long memory mode is not available at the fastest sweep speeds, not sure if there are any other draw backs (responsiveness?). If the Instek offers the 2Mpts at all sweep speeds by default, that would actually be a pro compared to Rigol.

I don't think anyone here has both scopes (and they didn't want Dave to review one, which is a con, although I don't think Rigol send him one either). The consensus based on specs and support seemed to be that Instek was somewhat better. The Rigol has a few weird features, eg. the measurements are based on the QVGA display, not on the raw data, it would be nice if Instek improved on that, but I don't know if that's the case.

[mikeselectricstuff]

Can't comment about the Rigol specifically, but in general long/deep memory is an extremely useful frature in a scope.
The most common way it helps is that it is much less necessary to get the triggering set just right, or even use triggering at all - you just grab a bunch of data and zoom in on the area of interest.
When debugging any sort of comms protocol, deep memory is pretty much essential to give a decent amount of traffic with sufficient resolution.

[cyberfish]

Thanks! I think I will go with the Instek then.

[DJPhil]

Thanks! I think I will go with the Instek then.

If you do, please keep us posted! Any info is good info, as there's not much out there for the Instek yet.
I was about halfway through saving up when I had to go to the ER on no insurance, so I'll be waiting til next year.

[cyberfish]

For sure. It won't be for another 2-3 weeks, though (applying for a USD credit card so I won't get charged insane exchange rate from my Canadian dollar card). No one in Canada (or anywhere for that matter) sells it at anywhere near tequipment's price.

I won't mind doing any tests that don't cost money/warranty/too much time.

[EEVblog]

User manual available here:
http://www.tequipment.net/RigolDS1052E.html

The 1Mpoint memory on the Rigol is only available in single channel mode at 500MS/s or below.
Dual channel it gets halved, and at 1GS/s it's only 16KB (which is a still fairly decent).

Dave.

[cyberfish]

Ah! That makes sense.

I guess they have 16KB SRAM and 1MB DRAM, and they can't manage to clock the DRAM fast enough for 1GB/s write.

If the Instek one can do 1GS dual channel for 2Mpts total, they must be using 2MB SRAM?

To do 2GB/s in DRAM would be very difficult (I only get 4GB/s on my desktop PC and that's with 4 sticks of memory with 8 chips each).

[mikeselectricstuff]

User manual available here:
http://www.tequipment.net/RigolDS1052E.html

The 1Mpoint memory on the Rigol is only available in single channel mode at 500MS/s or below.
Dual channel it gets halved, and at 1GS/s it's only 16KB (which is a still fairly decent).

Dave.

That's a reasonable compromise. IME you don't often need deep memory and high sample rate at the same time, and it costs a lot to provide deep memory at high speed.
It is however important the the scope's User Interface is snappy enough to be able to scroll & zoom through the memory quickly. Deep memory becomes a lot less useful it it's too sluggish to actually view it easily.

[rf-loop]

I recommend to read GW instek user manual and datasheet very carefully. And also after this can you exactly know how it works? Why?
 (Rigol datasheet and selling brochure is much more open mind and honest imho. There is clear table example about memory depth in different modes). Maybe it is "too difficult" fot GW to make this kind of clear table.

GW tell on the technical data only that:
"Record Length Maximum; 2M points (1 channel), 1M
points (2 channels)"

Compare to Rigol what give extremely clear table about sample rates and mem depth. Why GW want speak very high in every place about maximum 2M points. But then they do not speak loud about 4k points "normal" fast memory. (2x8k or 1x16k points in Rigol)
It seems that GW want littlebit hide truth but then becouse they have double slow memory they speak it so loud that peoples forget check how things are in real. So do not be fooled... If need more slow memory it is ok but if need more fast memory... Rigol have double.




I do not know exactly how it works if I read this from user manual (GDS-1000A series user manual):

"
Note: 2M point memory lengths are only available
for time bases slower than 10ns/div on a single
channel, and 1 M point memory lengths are only
available for time bases slower than 25ns/div on
two channels.

Who knows how it works if read this next?

"The memory depth is limited to 1 M points when
both channels are activated or 2M points when
only a single channel is activated. The signal must
be triggered /stopped to have access to the full
memory depth. Therefore when a signal is saved
the waveform will be automatically stopped if it is
not manually triggered /stopped first.
There are a number of conditions when all of the
available memory is not utilized due to a limited
number of different sample rates. This can be
caused by an un-triggered signal, or a time/div
setting that is too fast to display all the points on
screen."


Maybe this is clear:

"When in the Roll mode, an indicator appears at the
bottom of the display. When in roll mode the
record length is 2M (1 channel) or 1M (2 channel)."



I have not connection to Rigol... yes I have some Rigol also with many others (Tektronix and Hewlett - "Agilent" Packard)
GW is one Chinese name just as Rigol, Siglent (Atten), UNI-T and many many others.
(yes GW is made in Taiwan isle and there is only one China (PRC) what is internationally recognized as an independent state if US want or not.)

[cyberfish]

That is a very good point. I will try to contact GW Instek for clarification. If it's really like you said, though, I doubt they will reply.

In which case I will probably go for the Rigol.
(and by the way I am quite aware of the situation in Taiwan. I was born there and spent 14 years of my life there )

[cyberfish]

I found a review for the 150MHz version.

http://welecw2000a.sourceforge.net/docs/Hardware/GW_Instek_GDS-1152A.pdf

First thing to notice is, the sampling rate is 500MSa/s when using both channels, so the manual is a little deceiving, since I would think it's a really important thing to mention, and they didn't mention it at all.

The ADC configuration is the interesting part.

It uses the same ADC (AD9288), except the 100MSPS version, but only 4 of them (8 ADCs, since they are duals) instead of 5 in Rigol. Which one is better depends on what theory you believe in. If you believe speed grade is just marketing and doesn't matter, Rigol is better. If you believe speed grade matters, Instek is better (25% overclock vs 125% overclock).

The author, who sounds like he knows what he is talking about (he is the developer of an alternative open source firmware for Welec scope), thinks highly of the hardware design, especially the frontend. It would be great if we can compare it to Rigol's. Even a component listing can help. From a very superficial glance, I see quite a few aluminum polymer caps on the Instek, and all electrolytic on the Rigol.

I also read an informative thread on a Chinese (yes, I understand Chinese ) forum about this issue.
http://www.ourdev.cn/bbs/bbs_content.jsp?bbs_sn=3428440&bbs_page_no=1&bbs_id=3043
Most of what they talk about is the same as what we talked about here (whether speed grade matters, if it's ethical, lot's of angry posts, etc).

A few interesting notes -
1. Only 9 chips are sanded - the 5 overclocked ADCs, and 2 AD8370 (variable gain amplifier). The other 2 no one knows. DAC maybe? (for voltage offset, the Instek has it)

2. In a post, search for "?750??", someone tried running a 100MHz rated part similar to the AD9288 (AD9283BRS100) at 100MHz, 120MHz, and 150MHz, measuring a 1MHz active crystal oscillator with a 10:1 resistive divider without compensation. He noted that 100MHz and 120MHz graphs looked "normal", but 150MHz graph has significantly more noise, even on the unconnected second input (green). Unfortunately he didn't write much about the testing methodology.

Someone can conceivably do the same test with the chip in use, if you have time and an FPGA board lying around, and don't mind making a small PCB. The chips themselves don't cost that much.
--------------

My impression is the Instek's build quality is higher, but of course the Rigol has the 100MHz hack. I also have higher confidence in Taiwanese build quality vs China. How much is that worth is up to you.

They are both somewhat dishonest in my opinion - overclocking and sanding chips, and deceiving manual and specs. I guess it's lesser of the 2 evils, since we don't really have any other sensible choice at this price point.

I'm not sure if the 10ns/div limit on the long memory for the Instek really matters. 10ns/div means you can see 1 period / 2 divs on a 100MHz signal. Maybe it just means the long memory doesn't work with equivalent time sampling? The bandwidth is not even that high, and I doubt I will be working with that kind of high speed analog signals anyways. For digital stuff a logic analyzer would be more suitable. That said, I haven't got a reply from them yet. Maybe I should write them in Chinese, too.

By the way, Sparkfun's very interesting new product -
http://www.sparkfun.com/commerce/product_info.php?products_id=9857
$50 logic analyzer with open source software + firmware.

[scrat]

By the way, Sparkfun's very interesting new product -
http://www.sparkfun.com/commerce/product_info.php?products_id=9857
$50 logic analyzer with open source software + firmware.
[/quote]

I'm also in the choice between GDS-1062A and DS1052E. From what has been written above, there are no heavy reasons to buy an Instek, since some of the features they claim are at least not much clear.
However, anyone can see that two channels can become too few for some things, especially if you deal with mixed-signal. So, my idea was to add one day a board which could read digital signals, being triggered by the trigger output from the scope, so that it would be possible to have both data sent to a PC. This board from Sparfun seems a good candidate for reaching this purpose, but the problem is I can't understand if the Rigol and the Instek have a sort of trigger output (which is a typical feature). The Rigol has a strange BNC on its back, just take a look at the pic...

[joelby]

The Rigol has a strange BNC on its back, just take a look at the pic...

It's the pass/fail test output. Hook it up to a siren.

[alm]

However, anyone can see that two channels can become too few for some things, especially if you deal with mixed-signal. So, my idea was to add one day a board which could read digital signals, being triggered by the trigger output from the scope, so that it would be possible to have both data sent to a PC. This board from Sparfun seems a good candidate for reaching this purpose, but the problem is I can't understand if the Rigol and the Instek have a sort of trigger output (which is a typical feature). The Rigol has a strange BNC on its back, just take a look at the pic...

The Open Logic Sniffer (actually built by SeeedStudio) is a much better deal than the Rigol Logic Analyzer board (which adds like $300-400), although it's nice to have logic and analog signals on the same timebase. I think the software is still a bit rough around the edges, but is being worked on. I don't think any of them has a trigger out unless they state so in the manual. The BNC bus on the Rigol is labeled pass/fail output, so it's for use in an automated test setup, not much use outside that. The OLS might have the option for trigger out that you could connect to the trigger input on the scope.

[scrat]

I was looking for the opposite (trigger output on the scope, trigger input on the logic analyzer), since scope's trigger should be much better and much more flexible (and can be set on a further channel).
Although I thought it was a typical feature, I took a look in the lab at a Tektronix (TDS3032) which seems not to have a trig out, while an older Agilent (52622D, maybe an ancient of the Rigol) has it on its back.
If a k€ Tek doesn't have it, it's not fair to want it on a Rigol!

[alm]

I think a trigger out was a new feature on the TDS3000B series, together with superficial features like a USB port. Got to save something for the next version . Don't think the older Agilent series were made by Rigol, they probably didn't even exist back then. Connections like trigger out seem more common on older scopes, for some reason.

The scope triggering the logic analyzer or visa versa is both useful. The scope is better at triggering on analog parts (eg. level, rise time), but the logic analyzer is better at triggering on digital patterns. I just suggested reversing it because that might actually be possible without major surgery on the scope.

[scrat]

The scope triggering the logic analyzer or visa versa is both useful. The scope is better at triggering on analog parts (eg. level, rise time), but the logic analyzer is better at triggering on digital patterns. I just suggested reversing it because that might actually be possible without major surgery on the scope.

OK, this should work and will be the simplest way, but...
..at the cost of that useless BNC on the back, why didn't they put trig output on their scopes?  (couldn't the pass/fail test or calibration be done via a USB/serial signal?)
However, the Instek competitor doesn't have that output too.

[alm]

OK, this should work and will be the simplest way, but...
..at the cost of that useless BNC on the back, why didn't they put trig output on their scopes?  (couldn't the pass/fail test or calibration be done via a USB/serial signal?)

I agree, pass/fail is useless for hobbyists or R&D, although troubleshooting and production testing is probably a significant part of the market. I'd rather have a trigger out, too. Pass/fail could be done via USB/serial, but then you need a more intelligent to receive it. The BNC jack can be used to connect to simple things like a light or part of the conveyor system, without using a computer with custom software.

[cyberfish]

Got a reply from Instek (actually "TRADEPORT ELECTRONICS GROUP", which I am assuming is their distributor/representative in Canada, since I selected Canada on the contact form).

Hi Matthew,

Thank you for your interest in Instek test and measurement products.


The GDS-1000A series has 2 M long memory which is not dependent on sampling speed.  The 1, 2, and 4 that you mention refers to the save feature on the SD card.  The memory will be 2M long if capturing and saving one channel but will split to 1 M if capturing two channels. It has a fast save 4K feature which will capture short events.

The 1Gsa/s is applicable for one channel but is split to 500Msa/s for two channels.

So it seems like 2M is available at 1GSa/s. Guess we will find out soon enough! I have pretty much decided on the Instek (talk about switching back and forth). The only advantage of the Rigol is the 100MHz BW hack, but I don't think I will need that any time soon, so memory depth is more important, and build quality appears to be better.

[rf-loop]

I found a review for the 150MHz version.

http://welecw2000a.sourceforge.net/docs/Hardware/GW_Instek_GDS-1152A.pdf

First thing to notice is, the sampling rate is 500MSa/s when using both channels, so the manual is a little deceiving, since I would think it's a really important thing to mention, and they didn't mention it at all.

The ADC configuration is the interesting part.

It uses the same ADC (AD9288), except the 100MSPS version, but only 4 of them (8 ADCs, since they are duals) instead of 5 in Rigol. Which one is better depends on what theory you believe in. If you believe speed grade is just marketing and doesn't matter, Rigol is better. If you believe speed grade matters, Instek is better (25% overclock vs 125% overclock).

Thank you this pdf. In my own needs I am happy now that I select Rigol. (for some special use, becouse most time I use old Tek and HP)

About ADC. Rigol and Instek use exactly same ADC. (chip itself is exactly same... only speed stamp is different. It means that -100 chip reach ALL datasheet limits with this speed and -40 with its speed (quaranteed).  But first, oscilloscope do not need all these specs, they need only these things what are meaningful in this aplication. If we set different limits for some parameter we can drive it other than specified speed.

Rigol use exactly same chip with 100MHz and Instek use these 125MHz. (chip architecture is same!)

Rigol use -40 stamped and Instek use -100 stamped (specially selected chips). Maybe Instek need do this if they have no capacity to do they own chip tests for individual chips. (If Rigol buy chips and they can accept 50% of chips with they own aplication specified specs there is nothing wrong. It tell only that there are some very clever design engineer who understand how fundamental physic go in chips. Maybe he is not just after school.
If I run chip with all spec limits borders  and then with speed I go over... then I can maybe tell that I am overclocking.

(look datasheet max parameters and remember that specs means they all can be true in same time and chip works... all timing and temp etc things. If you find some max,min,quaranteed limit you do not need you can maybe find that you can use chip with different speed or some other parameter you can go over limits. If you need broke some other limit you maybe need adjust some other limit. You can try with some cheap components....

Example in old times I can use speed classified (memory) chips just as faster classified same chips becouse my temperature do not go at all this area where is datasheet max (also datasheets have some other min/max parameters what I did not need... if you know you do not need some you maybe can go over some other parameter becouse they affect each others. Did I "overclock". No. I only know how datasheet need read and how fundamental physic in chip go and then I make lot of tests so that I can proof it works.  Nobody tell that "oh you are overclocking"... they tell that oh you find very clever road to save lot of money... nice please... how you do it. And some "brown letter" I get later.

Think what is behind this -100 or -40 stamp on chip. How this classification after product is made.

Also if can not sell any -40 chip I think they do not stamp and package any.
Same for -100. If nobody never buy these they can sell all with -40 stamped and save some money from separating and logistik.

[cyberfish]

About ADC. Rigol and Instek use exactly same ADC. (chip itself is exactly same... only speed stamp is different. It means that -100 chip reach ALL datasheet limits with this speed and -40 with its speed (quaranteed).  But first, oscilloscope do not need all these specs, they need only these things what are meaningful in this aplication. If we set different limits for some parameter we can drive it other than specified speed.

That's one theory. Of course ADI won't agree with you, and we have no way of finding out if that's true.

Rigol use -40 stamped and Instek use -100 stamped (specially selected chips). Maybe Instek need do this if they have no capacity to do they own chip tests for individual chips. (If Rigol buy chips and they can accept 50% of chips with they own aplication specified specs there is nothing wrong. It tell only that there are some very clever design engineer who understand how fundamental physic go in chips. Maybe he is not just after school.
If I run chip with all spec limits borders  and then with speed I go over... then I can maybe tell that I am overclocking.

Yes, of course engineers start running chips out of specification when they get more experience... wait what?!

In a bag of 10% tolerance resistors you won't find any within 1% tolerance. Because those would be in the 1% tolerance bag.

It's the same with speed binning. Some ADCs can satisfy the noise specifications at 100MHz, and they get marked as 100MHz parts. Some can only do it at 60MHz, and they get marked as 60MHz. Some can only do it at 40MHz. Some can't even do 40MHz and they get thrown out of the window.

This is what the process is supposed to be like. And in this case, 100MHz parts will be much different from 40MHz parts.

Of course, it's also entirely possible that their manufacturing process have matured so much that they now produce more 100MHz parts than they need, and are down marking them to fill the lower market segments.

Which theory is true I have no idea and have no way of finding out, so I left it as an open question.

It sounds like you have special insider information from ADI that tells you the second theory is true?

Just because chips are made the same doesn't mean they will perform the same. That's what speed binning is for.

Example in old times I can use speed classified (memory) chips just as faster classified same chips becouse my temperature do not go at all this area where is datasheet max (also datasheets have some other min/max parameters what I did not need... if you know you do not need some you maybe can go over some other parameter becouse they affect each others. Did I "overclock". No. I only know how datasheet need read and how fundamental physic in chip go and then I make lot of tests so that I can proof it works.  Nobody tell that "oh you are overclocking"... they tell that oh you find very clever road to save lot of money... nice please... how you do it. And some "brown letter" I get later.

Yes, you are overclocking.

The datasheet says, it will run at 40MHz at -25C to 125C or whatever. It DOESN'T say it will run at 100MHz at 25C. You are GUESSING it will work and making that number up.

I'm fairly certain Rigol engineers don't have access to the ADCs design.

And I'm also fairly certain Instek has the ability to test ADCs if they have the ability to make oscilloscopes.

[rf-loop]

Rigol make oscilloscope and in this aplication they use many components. Rigol give specification for scope.

AD give specification for single ADC and with specified parameters. Chip desingn is 100Ms/s ADC. There is not any kind of overclocking if drive it with 100M. But AD do not quarantee that it can do it with all specs limits.

AD tell that maximum speed is minimum 40M, 80M or 100M so that they guarantee it for full specified temp range and with Vdd = 3.0V and Vd = 3.0V. (chip Vdd and Vd range is 2.7 - 3.6V abs max 4.0V) and they guarantee this minimum speed in whole temperature range up to +85 celsius.

AD tell maximum conversion rate 40, 80 or 100 minimum. They do not tell maximum. (if you find it can do it in your aplication and aplication specs so it is ok.) If manufacturer tell that maximum temperature is example 100 celsius and you use this kind of component 110 celsius we can tell that you run it overheating. manufacturer do NOT give maximum conversion limit! Not even typical. They tell only guaranteed minimum what reach all other parameters also with this speed and also they tell that it is only just with they testing methods. (who know what are test machine impedances and so on... )

AD tell also minimum conversion speed. It is 1MSPS. Oh my god... they are underclocking?
Now I can ask... why nobody tell that they are underclocking? I want big mouth talking all over internet that Rigol is underclocking  ADC's
(yes but in real they are not... AD give: Minimum conversion speed is 1MSPS maximum.

Of course SINAD, effective bits of conversion, second harmonic, signal to noise can differ what AD quarantee. But agen Rigol oscilloscope specifications are not AD's ADC specifications. Rigol give they aplication specifications - Not AD.

I can see that term "overclocking" have lot of misunderstoods... maybe becouse PC "overckocking".

Who make aplication is full responsible how it works or not and what is aplication specs.
There are lot of things out from datasheet. With different limits, different temp, different voltage etc. If I find that datasheet tell "some thing" 20ns maximum at 75 celsius. And if my lab test for componet tell that 15ns at 55 celsius and if I know my aplication need maximum 40 celsius. I use it in my aplication as 15ns component. What I am "overspeeding"... exactly nothing. I only use more cheap chip becouse I do not need all these things what are specified for more expensive chip becouse my aplication do not use these limits what are for datasheet specs.


It is totally different case also if manufacturer give direct minimum and maximum values example like this (AMD):



If you go under min limit you are underclocking and if you go over limit you are overclocking. (still it may also work if adjust some other limit different as datasheet. Voltage, temperature etc... or if can accept more errors.. (typically we do not accept processor errors becouse system crash... but A/D conversion is different...

AD have not tell maximum... it have only tell minimum! Where is so overclocking. Where is manufacturer set limit what you go over? Guaranteed minimum is not maximum value what you can use if you aplication accept it. And they have test it... they have sell some amount of these... have you any data that something is wrong? It do just as they promise. (there is not also any problem with higher speed becouse chip itself have designed for 100MSPS.

Very interesting small detail is that -40 classified chip have less power dissipation with 100MSPS  test run if compare to -100 labeled chips in 100MSPS test. (source also AD).

If some have measured ADC9288 Vdd and Vd voltage in Rigol scope, what you have find?

[cyberfish]

Chip desingn is 100Ms/s ADC. There is not any kind of overclocking if drive it with 100M.

Of course there is.

If you have an Intel CPU designed for 4GHz, but tested to only run at 2GHz, and sold as a 2GHz chip, and you run it at 4GHz, is that not overclocking?

I understand what you are saying about the ADC MAY be able to run at higher speed if you don't need the full temp range. The problem is, we don't know by how much, or even at all. Why 100MHz? Why not 200MHz?

The correct engineering practice is to adhere to the 40MHz guaranteed speed. If you run it higher because you GUESS it can run higher at your smaller temperature range, you are trying your luck. The manufacturer (ADI) doesn't guarantee anything at this speed. This batch can work, next batch may not. Or it can have a shorter life, or whatever. It's your problem.

It's not possible to test all ADCs. At best, they picked a few samples, and found they work fine. "Ah well, that will do". For the cost of testing all ADCs themselves, they could've just gotten 100MHz parts.

If it's such an honourable practice, why are they sanding their chips to prevent people from finding out? (and doing such a poor sanding job that people still found out)

Very interesting small detail is that -40 classified chip have less power dissipation with 100MSPS  test run if compare to -100 labeled chips in 100MSPS test. (source also AD).

That makes perfect sense. Higher power dissipation = lower impedance = better silicon. For example, it can allow them to charge up the charge and hold capacitor more quickly, allowing higher sampling rate at high accuracy. This just proved the point that there are actually differences between the 40 and 100 chips.

From Digikey,
AD9288BSTZ-40 = $6.32
AD9288BSTZ-80 = $10.09
AD9288BSTZ-100 = $17.09

The total cost of the 4 ADCs Instek is using (17.09 x 4 = 68.36) is much higher than Rigol's 5 ADCs (6.32 x 5 = 31.6). This is for single quantities, but the ratio should be similar at high quantity. The 100MHz parts cost almost 3 times as much as the 40MHz parts.

Wouldn't you think there is a reason for them to use 100MHz parts?

I have read quite a bit about Rigol in the last few days on Chinese forums (it's probably the most popular oscilloscope brand there), including other products like a 6 digits multimeter that can only do 4 digits, and a signal generator with fly wires everywhere, etc.

And the build quality of the scope -
http://home.comcast.net/~ajawam1/rigol/RIGOL_DS1102E_GUTS.html
compared to what's shown in photos in the PDF.

To be honest, I have very little confidence in Rigol as a company.

In my opinion, build quality says a lot about the company. If they can't even do the soldering and sanding right, do you really trust them to make a good oscilloscope? And they are cutting cost on one of the most important components, the ADCs, and sanding them to prevent people from finding out.

If the Rigol scope costs $100 less or something it can be a sensible choice.

At the same price, it would be hard to choose the Rigol.

Of course, Tektronix or Agilent would be even better. But they cost about twice as much.

[rf-loop]

But Agilent = Rigol... sometimes.

This is Agilent "quality. 

One point is that I do not at all understand why Rigol grind ADC labels off. This is just "stupid". Maybe they do it just for persons who do not understand these speed things. (have you see any Rigol DS1000E where 100MSPS/ADC fails? Do you know why? )

BTW as AD datasheet read. They test 100% (for this parameter), not only random samples. Also -40 chips. It all read in datasheet.

[cyberfish]

Yeah I know Rigol OEM low end Agilent scopes. Wonder how that works. Maybe they have higher quality control for those? Which makes sense because they have higher profit on those.

By testing ADCs I mean by Rigol, to make sure they run at higher frequency. I know ADI tests them, but only to rated frequency of course.

I don't think ADCs will fail. Probably just higher noise, which is hard to measure.

[cyberfish]

I was thinking about getting both the 40MHz and 100MHz versions and test them out to settle this issue once and for all, but no place has stock and AD doesn't have sampling for these chips.

EDIT: a few places have stock for the 40MHz one, but no place has 100MHz. AD lead time is till November for the 100MHz. On an interesting side note, it seems like Maxim's alternative is only 40MHz.
http://www.maxim-ic.com/alternatives.cfm/part/AD9288/pk/28

So it's not like anyone can make them.

EDIT2: Maxim does have 100Msps ADCs. Pricing is similar (high premium compared to slower parts). Maybe yield for those parts still aren't that high?

[Zad]

I was thinking about getting both the 40MHz and 100MHz versions and test them out to settle this issue once and for all, but no place has stock and AD doesn't have sampling for these chips.

EDIT: a few places have stock for the 40MHz one, but no place has 100MHz. AD lead time is till November for the 100MHz.

I'm getting a bit worried about AD. Here is an edited part of my current shopping basket with them:

AD8342ACPZ-REEL7                                           
Product Status: Production     
Availability: In 16 weeks

AD8343ARUZ                                
DC-to-2.5 GHz High IP3 Active Mixer       
Product Status: Production     
Availability: In 12 weeks   

AD8351ARMZ                                
Low Distortion Fully Differential RF / IF Amplifier       
Product Status: Production     
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I have the AD9910 DDS on my shopping list too, nowhere has them in stock.

For fast ADCs, try Texas Instruments, they have a huge range.

[rf-loop]

I don't think ADCs will fail. Probably just higher noise, which is hard to measure.

Yes, this kind of things there are and maybe there is also more differencies between individual scopes if compare to case if they use ADC as they are selected by AD. But we need remember, they sell scopes with scope specs, not with ADC specs by AD..

AD have not set max for ADC clock. They tell only minimum quaranteed max conversion specs where all given data are qualid.
If you test 1000  -40 chips you may be find that in your temp area and you voltage and your more loose limits they do it example 100MSPS (conversion quality is maybe not same as datasheet but still acceptable for scope with scope itself specs.

One important thing for noise is ADC clock signal quality. And I quess that part of modified (and not modified) Rigol noise come there. Specially it can see with modified 1052. Maybe some individual scope kore and some less.

Why/how Rigol select what scope they give name DS1102 and what is then 1052
But I have compare (without good data out from test) original DS1102E and DS1052E modified to DS1102E.
By the eyes only without good test I have one "opinion". DS1102E/mod have more noise. It looks like sampling noise is more high. But this I can not proof becouse I do tests only from scope input.

[cyberfish]

Yes, this kind of things there are and maybe there is also more differencies between individual scopes if compare to case if they use ADC as they are selected by AD. But we need remember, they sell scopes with scope specs, not with ADC specs by AD..

That's true. But you can also say bad soldering and fly wires are fine, too, as long as the scope works.

It's just that seeing those things lowers my confidence in them.

AD have not set max for ADC clock.  They tell only minimum quaranteed max conversion specs where all given data are qualid.
If you test 1000  -40 chips you may be find that in your temp area and you voltage and your more loose limits they do it example 100MSPS (conversion quality is maybe not same as datasheet but still acceptable for scope with scope itself specs.

That's possible, but they will have to test every single ADC, which I'm guessing they (Rigol) don't. For the cost of testing them they could just get 100MSPS parts.

It really depends on how good ADI's manufacturing process is. If most chips end up in the 40MHz bin, with very few ending up 100MHz, you probably won't find any that can do 100MHz in the 40MHz bin, because they would be in the 100MHz bin.

I'm guessing they just took 40MHz parts, and accept the higher noise, because most people probably won't notice. Or enough won't for the rest to not matter.

[scrat]

I'm still in the middle between Rigol and Instek. The first has lower price, but seems to have also lower performances and builing quality.

Apart from the building quality (soldering, wires, etc) in my opinion there are a few things which must be taken into account.

If we were direct Rigol customers, so that we ordered a scope with some specs and followed its development, we could object to them for their choices, if we think quality level is insufficient with respect to requirements. But since we go on the market and take what is specified by someone other, unless it doesn't comply with specs (the whole product, not a single part), we can't say much.

One other thing is on ADC. Rigol scope versions management (which consists of only programming a different ID on 50 and 100 MHz machines) teaches that successful companies simply look at market demand, and try to satisfy it. It is also well known that many semiconductor companies sell different versions of their chips, but real difference is only a code in a non-volatile memory. All of the digital and some of the analog ICs have testing modes, which can be accessed via a peculiar sequence and allow for test after production, since the accepted failure rate on the market is usually low (1/1000, almost never it is 0%, also because it's impossible or too expensive to test for all of the working conditions). In some cases these modes also can be written on calibration data or "version" data, enabling or disabling some features (sometimes competitors have discovered this by looking at chips' microphotos which looked the same for different versions). In some other cases they simply mark differently their ICs to cover as many market segments as possible, like someone already posted here. Rigol uses those 40MHz parts at 100MHz, and it could be that ADCs are only marked differently, or that they do not perform the same way, but if the scope stays inside the specs, for what can we complain them? Of course, there can be failures, but which company on this world is able to produce only perfect products (staying in the low-cost market, too)? Companies guarantee for their products, which means there is a low probability of failure or no compliance, and they will pay for it. I will otherwise complain Rigol if for a defective product they do not obey their guarantee.

Are there some photos or reviews of the Instek? Is it really far better quality?
If possible, it would be nice to test the scope (instead of the ADCs) to see if it complies the specs...

[cyberfish]

There are pictures of the internals of both scopes a few posts up.

I'm probably getting the Instek soon, so we can potentially test it and compare it with Rigol (that many people have), then. But I don't really know how to test oscilloscopes, and I'm not taking it apart .

[rf-loop]

CPU overclocking is totally different case. It crash if some inside databus data is wrong becouse parallel digital data is not qualid exactly this time when it need be. (I do not explain all things, it is extremely complex to explain with bad english. There is also many other problems as temperature. Hot spots inside chip and also many wear and tear things on the chip.)

This AD's ADC is "100 MHz" chip, if it is labeled -40, -80 or -100. This chip digital parts work very easy with 100MHz without any digital data qualid problems inside chip. Indirectly this can read also datasheet. Also this kind of company as Rigol (no 1. or 2. in world for manufacturing oscilloscopes. They make also OEM). They can do all specifications tests for chips just same quality (or more) than chip manufacturer. (yes I wait time when Rigol co to they own chip designs or even manufacturing as HP or Tektronix before)
Also they can order standard chips with they own label. If they do this nobody tell any overclocking becouse nobody can not see any overclocking problems)

This "overclocking" what is not really overclocking in normal "CPU or Memory" meaning. And also not as PCB overclocking. Yes there is many times problems becouse PCB RF design is not good or not good for overclocking and bus timing may also fail there. 100ps is long time and travel distance on the PCB trip may be 20mm (trivial example) and more complex it go with strip lines becouse there is resistance capacitance and inductance. Also transmitting part have these and receiver chip.

CPU itself or whole system overclocking is totally different case and it may affect component lifetime and system reliability.

But what happend if put -40 ADC (what is really same chip as -100 chip). It works fine and without problem in most case in digital side. No corrupted data no timing problem what can conflict with data reading chips.
Problem is in ADConversion. (in most case) And if problem is other type these cips come not out from AD. If there still are chips what fails with 100M they can test out before go to scope PCB. After scope PCB is ready and if there is "bad" chips they fails and do not go to customers. (just as all do..., Nokia, Tektronix, Agilent etc)

Interesting part of this case is Analog Digital Conversion (ADC) itself quality.
-40 Chip do not reach same ADC quality as -100chip with 100MSPS. -100 chip ADC quality you can read directly from datasheet and this AD quarantee. (example around 7bit total accuracy or littlebit worse. Dynamic perfomance part of datasheet is meaningful and I "quess" there these -40 chips used as -100 chips do not reach same quality at all. SINAD/SNR and harmonic distortion may differ lot of.

But now it is important to understand that we do not look ADC specs. They are not promised Rigol scope specs.
Rigol do NOT promise even nearly same for oscilloscope.
Inside scope specs "window" +-4% or +-3% is lot of room for bad and poor ADC. Only they tell that still ADC resolution is 8bit. Yes it is, it can product to databus 8 bit bytes. But real accuracy is nearly as 4 or 5 bits. +-4% window have lot of room for also these things what come from ADC. (encode pulse timing is too short for this -40 labeled chip if we think what conversion quality is promised if it is used with more slow encode signal.)

This is quessing. Most reasons for -40 label on originally -100 designed and producted chip is inside anlog channel and S&H complex ("bad silicon" ... but maybe there can find also more selective and accurate explanation. Strip lines and components quality in analog part and capacitor and switch (sampling) components. More fast run more lost in analog and conversion accuracy there. And Rigol do NOT promise accuracy what can do with -100 chips. (but also Instek do not promise

But what do Instek.
They overclock. Chip is 100M chip (also this -40 chip) and digital parts (databus and timing there) is quaranteed with chip design for this speed. Instek go over this! Rigol do not go over this. Going over this limit is more danger (but Instek go only littlebit (125/100) and maybe this do not make also any problem aspecially if (data etc) timing outside of chip is good (also need remember that specs data are made for 3.0Vdd but chip normal use area go up to 3.6V (not as abs max).

Rigol go over analog specs. Instek go over chip designed digital speed. What happend if data is not qualid. It can be random 8 bits. In Rigol case there is more like only analog conversion itself quality problem if compare to datasheet quality promises. (and these Rigol do not promise.) Rigol promise DC aacuracy +-3  to +-4%. (these limits includes also ADC conversion itself error. Btw 8% from 255 is 20,4.  4bit is 16. So there is huge room also for ADC origin error. Wery easy can drop one bit out and after it we can accept -40 chip used as -100 chip but specs read not now signal to noise ratio 44dB or differential nonlinearity typical +-0.5LSB)

If there happend some other "mystified" things as they do "overclocking" I am very interested to find any mystified problem origin from this "overclocking".

Yes I know lot of stability problem and crashed computers. But please do not compare these if you really do not know AND understand  theoretical and practical difference to this case.

Rigol, Instek and others they sell oscilloscopes and they have published specs for they product. I buy oscilloscope not ADC chips. If Oscilloscope specs meet my needs and I believe quality is ok and price...  yes of course I sometimes want buy also name.
One but small scope manufacturer in world is Tektronix. But in the "golden years" it have good name specially with scopes. Yes there are maybe also some reasons for this thinking about "good" with this name but... in the truth.. they have made many many bad designs and bad production but I do not have pictures about extremely bad "hop wires" and bad solderings and bad designs and specially bad component selections.

More difficult is "overclocking" but you can not know it becouse chips are Tektronix design and tektronic manufacturing.
How peoples can buy oscilloscopes what are made with components "no datasheet".
What is designed durability. 10000hr? (what you think about 500MHz vertical amplifier hybrid chipa (this case mixed digital and analog) where case temperature in normal use is more than 90 celsius in normal room temperature.
Yes you can buy these Tektronix good brand oscilloscopes in ebay. Very typical is that seller put picture where scope is power off. "we have no knowledge or possible to test"...hehe)

I have never understand this big mouth talking about "overclocking".
There is only clever engineers who find this solution. There is also lot of power for testing.

But where are these units what have real problems. I have use lot of time for surfing internet and find anything but only peoples self made fails. Where are these reliability problems. Scope have sell lot of and long time. Where are these bad solderings errors and ADC fails becouse "overclocking" ... I have seen lot of Intel and AMD crashed with overclocking...  burned CPUs burned display drivers etc and etc. But I have not seen or heard any crashed ADC or burned ADC about Rigol. Mybe there are fails... of course there are normal fails but if this is any kind of problem there is full of internet talking it.  How many they have sell total DS1052E and 1102E?

I hope some specialist (who also really know) write with better english also this kind of things what are in theoretical and practical things related to this kind of using AD9288 out of its specification sheet.

But my tight opinion with my all knowledge is that comparing to CPU's and this kind of overclocking is not relevant.

[cyberfish]

The problem is, no one here knows how to properly test oscilloscopes, so we have to rely on indirect observations, like build quality, soldering quality, component selection, etc. And Rigol is not looking good in that department.

Perhaps we can do some simple tests after I got mine? But of course, such test won't be too accurate because of many factors (different signal sources, different places/temperature/humidity, etc).

[alm]

Perhaps we can do some simple tests after I got mine? But of course, such test won't be too accurate because of many factors (different signal sources, different places/temperature/humidity, etc).

The trouble with testing scopes is that you need signal sources that are better than the scope under test, to be able to test the limits of the scope. I've seen some tests that suggested the attenuator wasn't very linear over the frequency range, but this was with an unknown, uncalibrated pulse generator, so it's hard to tell what's going on. Running through the performance verification procedure (or calibration procedure without doing any adjustments) in the service manual is my usual method, except that Rigol doesn't publish any procedures (neither does Agilent with the re-branded versions). Plus I don't have a Rigol scope. Required equipment would probably include:
- Leveled sine wave source from <=1MHz or so up to well beyond 100MHz
- Fast pulse source with edge rate much faster than 3.5ns
- Accurate DC source (this one is easy, stable lab supply + basic DMM should be plenty accurate)
- For testing attenuators, you might also need to be able to generate fast pulses with a large amplitude, or large amplitude leveled sine waves

This is unlikely to be cheaper than to buy a good brand name scope in the first place. This is not something that can be done with your average function generator. Plus they either need to be calibrated or verified with a known good scope that's much faster than the Rigol. Ideally, these tests should be performed over the operational temperature and humidity range.

The avalanche pulser design by Jim Williams (from memory it was in LT AN-47) discussed before on this forum is the best you can make as DIY design for a few bucks, but you really need a much faster scope to determine the output parameters before using it to verify a scope (he used an ancient sampling scope).

I prefer to just buy from a manufacturer that I can trust, although I do verify as much as I can.

[cyberfish]

Just got my GDS-1062A today. Have only been playing with it.

No major (or minor) complaints so far. I'm pretty happy with it, but then I don't have anything to compare it to (except the Tektronix in school lab).

Scrolling is smooth. Tried different time bases, etc. No noticeable lag any time.

I want to test it out for future potential buyers' benefit, but don't really know how. And I don't have a signal generator (I do have MCUs, passive components, diodes, transistors, common chips, etc). Any suggestions? I don't even have something that can generate short enough rise time to test the bandwidth!

Just a note before I forget - Yes, 1GS/s can be used with 2M long memory mode. 100us is the maximum timebase for 1GS/s (2ms recorded). It switches to 500MS/s at 250us.

For equivalent time sampling -
25ns -> 1GS/s
10ns -> 2.5GS/s
5ns -> 5GS/s
2.5ns -> 10GS/s
1ns (min) -> 25GS/s

So when the manual says the long memory cannot be used at <25ns, it just means it cannot be used with ETS. So yes, it is better than Rigol in this regard (1GS/s with 2M).

At 1x probe, DC coupling, averaging off, 1Gsps, probe shorted to ground clip, 2mV/div, 1ms/div, I am getting
Vavg = -117uV, Vp-p = 400uV
If that means anything (I'm curious. Anyone want to do the same on Rigol and see what you get?).

Interestingly, if I switch to ground coupling, Vavg becomes 89.1uV, and Vp-p = 0.

[joelby]

One thing I've seen done when trying to find a signal's noise floor is clipping the probe tips together and the grounds together and looking at the amount of stray noise.

It's not clear if it's the room I'm in or my scope, but my Rigol DS1102E registers about 7.5 mV RMS of noise, pretty much all 50 Hz. I compared this to a much more expensive Tektronik scope (both in the same room) and it was far, far better, though I don't remember what the signal was.

At 1x probe, DC coupling, averaging off, 1Gsps, probe shorted to ground clip, 2mV/div, 1ms/div, I am getting
Vavg = -117uV, Vp-p = 400uV

The DS1102E registers Vavg 360uV, Vpp 2.00mV, which does seem a bit noisier than yours.

Interestingly, if I switch to ground coupling, Vavg becomes 89.1uV, and Vp-p = 0.

Does it have a self-calibration routine? The DC offset on mine seems to drift a fair bit over time.

[cyberfish]

One thing I've seen done when trying to find a signal's noise floor is clipping the probe tips together and the grounds together and looking at the amount of stray noise.

Is that to measure background noise?

I get 10mV Vpp, ~2mV Vavg if I do that. But it jumps around quite a bit if I just put my hand near it.

It's not clear if it's the room I'm in or my scope, but my Rigol DS1102E registers about 7.5 mV RMS of noise, pretty much all 50 Hz. I compared this to a much more expensive Tektronik scope (both in the same room) and it was far, far better, though I don't remember what the signal was.

I live in a country with 60Hz AC, but my noise is pretty much uniform on FFT. No spikes.

Does it have a self-calibration routine? The DC offset on mine seems to drift a fair bit over time.

It does, but I don't have a BNC-BNC cable, so I can't really use it.

[alm]

Just got my GDS-1062A today. Have only been playing with it.

Congratulations!

I want to test it out for future potential buyers' benefit, but don't really know how. And I don't have a signal generator (I do have MCUs, passive components, diodes, transistors, common chips, etc). Any suggestions? I don't even have something that can generate short enough rise time to test the bandwidth!

The Jim Williams design in an appendix of LT AN-47 (other description here) is the closest thing you get to a fast pulse generator from jellybean parts. But the parts aren't terribly common, and you really need a fast scope (eg. sampling scope) to determine the real amplitude. The amplitude depends on the individual transistor behavior and strays, and is critical for calculating rise time (which is based on 10% to 90% of the original amplitude). Jim Williams has an improved design with a piece of hard coax as charge line, but it's more complex. This one generates a step instead of a pulse. Probably not worth the effort, I wouldn't worry about something as basic as bandwidth, they probably got that one right. Something like linearity of the attenuator over frequency range is more interesting (I suspect the Rigol is not great in that regard), but hard to do without expensive equipment.

I would check Dave's review of the Rigol and see how it compares on the good and bad points he mentions. Also subjective things like build quality (on the outside), user interface, responsiveness (especially with long records and things like measurements or math) and fan noise.

Some complaints I've heard about the Rigol are that triggering is not terribly stable (the wave always dances around slightly, even with a stable and noise-free signal) and that the measurements are based on the image on the screen, not the original signal. Things like bad accuracy compared to precision, and measurements that change depending on the vertical position on screen. Since I don't have a Rigol scope, I can't give you specific examples. It would be useful to know if the Instek scope has the same issues.

So when the manual says the long memory cannot be used at <25ns, it just means it cannot be used with ETS. So yes, it is better than Rigol in this regard (1GS/s with 2M).

Thanks for clearing that up! That's a clear pro over the Rigol. Nobody cares about ETS (at least I don't), so that doesn't matter.

At 1x probe, DC coupling, averaging off, 1Gsps, probe shorted to ground clip, 2mV/div, 1ms/div, I am getting
Vavg = -117uV, Vp-p = 400uV

Note that that makes a pretty good antenna. Doug Smith (EMC guru) actually uses it as a magnetic field detector. So it's probably not a great test. Look at what Dave did in one of his unexplained scope phenomenon blogs with the aluminum foil. Even better would be attaching a BNC short or terminator (50ohm is pretty close to a short for a 1Mohm input) directly to the female BNC connector.

Interestingly, if I switch to ground coupling, Vavg becomes 89.1uV, and Vp-p = 0.

Try letting it warm up for an hour or so, and then run signal path compensation (or however that's called on the Instek scope). That's designed to null temperature-dependent offsets, and usually recommended every time the ambient temp changes by more than a few K or so and you want to do accurate measurements.

[cyberfish]

The Jim Williams design in an appendix of LT AN-47 (other description here) is the closest thing you get to a fast pulse generator from jellybean parts. But the parts aren't terribly common, and you really need a fast scope (eg. sampling scope) to determine the real amplitude. The amplitude depends on the individual transistor behavior and strays, and is critical for calculating rise time (which is based on 10% to 90% of the original amplitude). Jim Williams has an improved design with a piece of hard coax as charge line, but it's more complex. This one generates a step instead of a pulse. Probably not worth the effort, I wouldn't worry about something as basic as bandwidth, they probably got that one right. Something like linearity of the attenuator over frequency range is more interesting (I suspect the Rigol is not great in that regard), but hard to do without expensive equipment.

The circuit looks pretty simple, but i don't have a boost converter to get 90V DC. Actually, wouldn't it be easier to just rectify and filter my 110V AC from the wall? I don't have enough training to play with mains voltage, though. So I will leave that alone.

I was hoping to be able to find out the "actual" bandwidth.

Perhaps a high speed FPGA's output would be fast enough? Sadly I don't have one around me either.

As for the subjective things -
Build quality is good. Nothing filmsy. User interface is well laid out. Didn't notice any peculiar sequences needed to access any function.
Responsiveness is good when scrolling without math. No noticeable lag any time. With FFT it starts lagging noticeably at high time bases. Gets to about 2 frames per second.
Fan noise I don't know. I am in a room with 5 computers and probably 20 fans =) It sounds like jet engine.

I can try the other things you mentioned (triggering, measurements, accuracy), but do you have more detail on how to test?

Note that that makes a pretty good antenna. Doug Smith (EMC guru) actually uses it as a magnetic field detector. So it's probably not a great test. Look at what Dave did in one of his unexplained scope phenomenon blogs with the aluminum foil. Even better would be attaching a BNC short or terminator (50ohm is pretty close to a short for a 1Mohm input) directly to the female BNC connector.

That makes sense. Will try that tonight.

Try letting it warm up for an hour or so, and then run signal path compensation (or however that's called on the Instek scope). That's designed to null temperature-dependent offsets, and usually recommended every time the ambient temp changes by more than a few K or so and you want to do accurate measurements.

I don't have a BNC-BNC cable, so I can't really do that. For some reason just using the 2 probes with the tips and ground clips connected doesn't work. Impedance too high probably.

[Bored@Work]

The circuit looks pretty simple, but i don't have a boost converter to get 90V DC

The thing doesn't require any specific DC/DC converter, just a low amp, approx. 90V one. Jim Williams has published a few variants of the circuit over time in other application notes, sporting other DC/DC converters and triggerable versions. Some have DC/DC converters without the diode voltage doubler, and use converters going straight to 90V.

Years ago I build one such avalanche generator. Not having the particular IC from AN-47 at hand, and not having a HV DC/DC converter IC at hand, I designed my own DC/DC converter. I used some bog-standard DC/DC IC, dimensioned it as a 9V -> 30V boost converter, followed by a diode voltage-tripler and closing the feedback loop over the tripler and the IC with a 90V:1.25V resistive divider. Pretty much what is in AN-47, just with a tripler instead of a doubler.

Efficiency of my converter wasn't great. I overestimated the power requirements and ended up with the converter working in non-continuous mode. Using a 9V battery as power source also wasn't too clever (they have the worst energy density of batteries). Still it worked good enough.

I would say, except for the 90V it is a fun weekend project. But remember, 90V are already in the dangerous voltage territory, and if you mess up the converter you can easily get higher voltages before the magic smoke is released from the circuit.

[cyberfish]

1. Measurements are done on the actual data. I can still get the 1kHz frequency reading from the compensation output even if I zoom out to 100ms/div (becomes big yellow band).
2. I have no way of measuring accuracy, but vertical offset (tried from -30V to 30V) does not change the readings appreciably (on the compensation output).
3. Used soundcard to generate 8kHz, 2.3Vpp sine wave. Appears to trigger reliably. I put it on continuous trigger mode, and moved the trigger from peak to peak. Waveform display is always very stable, and trace is thin. Tried manual triggering a few times, too. All images look identical.

The thing doesn't require any specific DC/DC converter, just a low amp, approx. 90V one. Jim Williams has published a few variants of the circuit over time in other application notes, sporting other DC/DC converters and triggerable versions. Some have DC/DC converters without the diode voltage doubler, and use converters going straight to 90V.

Years ago I build one such avalanche generator. Not having the particular IC from AN-47 at hand, and not having a HV DC/DC converter IC at hand, I designed my own DC/DC converter. I used some bog-standard DC/DC IC, dimensioned it as a 9V -> 30V boost converter, followed by a diode voltage-tripler and closing the feedback loop over the tripler and the IC with a 90V:1.25V resistive divider. Pretty much what is in AN-47, just with a tripler instead of a doubler.

Efficiency of my converter wasn't great. I overestimated the power requirements and ended up with the converter working in non-continuous mode. Using a 9V battery as power source also wasn't too clever (they have the worst energy density of batteries). Still it worked good enough.

I would say, except for the 90V it is a fun weekend project. But remember, 90V are already in the dangerous voltage territory, and if you mess up the converter you can easily get higher voltages before the magic smoke is released from the circuit.

That sounds like fun!

I'm not ready for high voltage, yet, though. So I think I will pass on that for now.

[alm]

The circuit looks pretty simple, but i don't have a boost converter to get 90V DC. Actually, wouldn't it be easier to just rectify and filter my 110V AC from the wall? I don't have enough training to play with mains voltage, though. So I will leave that alone.

I would recommend against that for safety reasons, you would have to treat the whole setup as dangerous mains voltage, and you would short neutral to ground by connecting it to the scope (don't even think about floating the scope/disconnecting the ground connection).

I was hoping to be able to find out the "actual" bandwidth.

You either need a very fast edge (significantly faster than the rise time of your scope, usually 3.5ns for 100MHz bandwidth) or a leveled sine wave from low frequency (<=1MHz or so) to beyond the bandwidth of your scope.

Perhaps a high speed FPGA's output would be fast enough? Sadly I don't have one around me either.

You need a rise time faster than 1ns or so, but a relatively long pulse length. I'd just stop worrying about it.

As for the subjective things -
[...]

Sounds good so far.

I can try the other things you mentioned (triggering, measurements, accuracy), but do you have more detail on how to test?

Someone with a Rigol scope would probably able to provide better reference values, my information about issues with the Rigol scope is purely based on what I heard.

I don't have a BNC-BNC cable, so I can't really do that. For some reason just using the 2 probes with the tips and ground clips connected doesn't work. Impedance too high probably.

Does it require BNC connections? Usually it just requires all cables to be removed, but I'm not familiar with the Instek scope.

[DJPhil]

Cyberfish: I'm loving all this information, would you consider starting a new thread with a summary of your observations?

I just feel like we're wandering off topic and I'm pretty sure we'll eventually have a lot of questions pile up soon.

Good idea?

[cyberfish]

Cyberfish: I'm loving all this information, would you consider starting a new thread with a summary of your observations?

I just feel like we're wandering off topic and I'm pretty sure we'll eventually have a lot of questions pile up soon.

Good idea?

Terribly good idea.

Let's continue the discussion here
https://www.eevblog.com/forum/index.php?topic=1358.0