Hunting for 200MHz+, 16bit, 4ch DSO -> What's good? - Page 1
Forum section: electronics / testgear

author: CPitts
author_rank: Newbie
timestamp: December 29, 2015, 06:26:29 am
content: Guys,I'm about to embark on my first DSO purchase and after some hunting, I believe I need a DSO that:- is 200MHz+- 15/16bit resolution- 4 Input Channels- DSO- USB based (don't want to worry about screen sizes, etc.)- High sample rate 1Gs/s ??Key activities it will be doing are:- high accuracy audio equipment testing (amps, CD Player, other digitial source [ADC, DAC])- digital circuit testing, analysis and troubleshooting (Arduino, Raspberry Pi, similar)- Digital IC I/O activity- Act as a high fidelity signal sourceMy current scope of choice is a USB based scope, the PicoScope 5444B.Given I'm in Australia, there seems to be little or no 2nd hand market for this stuff and prices a bit steep for every and anything. I'm reaching out to you guys to get advice on what other models exist in this range that are reliable supported in Aus?

author: Smith
author_rank: Frequent Contributor
timestamp: December 29, 2015, 06:59:57 am
content: Wouldn't it be easier to do the audio part (16bit) with a good quality computer audio card? You can even go to 24 bit, and its only as expensive as you make it.Besides that an USB scope is handy in size, NOT in use. It will never get close to a real scope. Update rates are normally verry bad, and I personally don't like the interfaces. A lot of newer scopes have a video output, so screen size won't be an issue. Normal scopes are 8-10bit, but normally this is more than enough. It's important to look for a scope with a good mV scale to look for noise in audio, and a nice FFT function would come in handy (but the PC DAC would probably be good in FFT too).

author: ataradov
author_rank: Super Contributor
timestamp: December 29, 2015, 07:00:26 am
content: Quote from: CPitts on December 29, 2015, 06:26:29 amProbably does not exist considering other requirements. And also is not needed for applications outlined below.Quote from: CPitts on December 29, 2015, 06:26:29 amBig mistake. There is no replacement for dedicated controls of the real scope. Get one with VGA output and don't worry about the screen size, if you discover that it is even a problems at all.Quote from: CPitts on December 29, 2015, 06:26:29 am

author: Fungus
author_rank: Super Contributor
timestamp: December 29, 2015, 07:27:15 am
content: Quote from: CPitts on December 29, 2015, 06:26:29 amYou might want to read this thread before you decide anything:https://www.eevblog.com/forum/projects/analog-disovery-as-audio-analyzer/These are well regarded for logic analysis:https://www.saleae.com/Throw in a decent signal generator and a DS1054Z for good measure and it will still cost much less than a PicoScope 5444B with 200MHz+siggen.Yes, it will take up a teeny bit more space but the result will be a lot more useful/powerful+useable. A mouse clicking on things thatlooklike knobs is simply a bad interface to an oscilloscope.

author: nctnico
author_rank: Super Contributor
timestamp: December 29, 2015, 09:25:22 am
content: I'd use dedicated hardware for audio equipment (like a good USB soundcard) and software; this will prove far more useful for measurements on audio signals than any oscilloscope will even be. Another option is to get an audio analyser-ish machine from Ebay.For the rest I agree that an USB scope in general sucks for use as a general purpose scope. Some people even build boxes with knobs to control their USB scopes

author: CPitts
author_rank: Newbie
timestamp: December 29, 2015, 11:57:36 am
content: Thanks for the quick responses guys!When I'm talking about audio, what I'm doing is feeding a (very) clean waveform into amps or circuits and seeing how well the outbound signal compares to the original input signal. Effectively testing THD, Noise, etc. I'm trying to avoid PC or other sources that may be noisey to start with.As for the 16bit requirement, the Picoscope does that but I'm looking for other options. Surely there are some?USB based makes more sense for how I do things and portability with a laptop or around the places I work. Not sure I understand why it would be a big mistake if I could do all the same adjustments with a USB based scope?

author: CPitts
author_rank: Newbie
timestamp: December 29, 2015, 12:20:51 pm
content: Quote from: Fungus on December 29, 2015, 07:27:15 amExcellent info Fungus! Thanks!!I just did a quick scan of the items you listed and watch your vid/read your post. Must say, you've done some great work there and are showing some of the info that I'm looking to extract from the testing I want to do. Checking out the prices of the units you've listed, seems like the DS1054Z and the 16 input Saleae would put me around the $US1050 mark + postage, etc to Aust. I see you're price argument there, plain and simple.As much as I'm a fan of coding (done too much of that), I'm more interested in a 'delivered' vendor product to give me all that stuff (FFT, Spectrum analysis) as well as detailed view into a waveform that's coming out of the device being measured.I guess I need more convincing that having a few more bits will give me what I need and not remove the convenience of an all in one scope (for analog an digi work), sig-gen, analysis tool, etc.Also, what is it with the love for the Rigol stuff? So much passion on here for it from the posts I've read so far (in other threads)

author: Smith
author_rank: Frequent Contributor
timestamp: December 29, 2015, 12:27:45 pm
content: A USB scope will work, but most of us hate/dislike the interface. A normal scope is much easier and faster to work with, so most of us will tell you to buy a normal scope. Maybe you should try one out before buying one. Maybe you will like it after all, but maybe you don't and save some bucks. I have tried some expensive ones, and I didn't like them,but maybe it's because I am used to normal scopes, as I have been using normal scopes for some 20 years.Normal scopes don't have to be large. There are a lot of new scopes that are quite small and portable.Regarding the signal generator, a good soundcard can do the same. You probably only need the 20Hz to 20kHz band after all. I have seen more people do this, and it seems to work quite well.There are a lot of types of scopes. Rigol seems favorite here, but I have good experience with Hameg scopes. But all in all, with Rigol you get a lot of scope per buck. You can also get descent second hand scopes if money is a issue.

author: trevwhite
author_rank: Frequent Contributor
timestamp: December 29, 2015, 12:35:28 pm
content: I thought picoscopes did some usb scopes that are good for audio.

author: dom0
author_rank: Super Contributor
timestamp: December 29, 2015, 03:56:00 pm
content: If you want dedicated hardware then you actually want a normal scopeanda used audio analyzer.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 29, 2015, 04:18:54 pm
content: http://teledynelecroy.com/oscilloscope/oscilloscopeseries.aspx?mseries=419

author: ataradov
author_rank: Super Contributor
timestamp: December 29, 2015, 10:10:13 pm
content: Quote from: CPitts on December 29, 2015, 11:57:36 amThere are no fast 16-bit ADCs. There are many technical reasons for this.If you look closely, their claimed SFDR increases only by 10 dB when going from 8- to 16-bit mode. This is a joke. They are doing some software averaging on 8-bit samples and "achieve" higher resolution this way. But that software averaging does not account for deficiencies of the 8-bit analog front end.Most modern scopes can do similar thing. It is usually called "High resolution mode" or similar. It improves things a bit, but nothing special.

author: ataradov
author_rank: Super Contributor
timestamp: December 29, 2015, 10:12:51 pm
content: Quote from: CPitts on December 29, 2015, 12:20:51 pmThey make good scopes, sell them at very good prices, and as a company, don't behave like dicks (Siglent, he he).

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2015, 10:23:32 pm
content: Quote from: ataradov on December 29, 2015, 10:12:51 pmBest you read the thread you're referring to again, Rigol did the same.

author: nctnico
author_rank: Super Contributor
timestamp: December 29, 2015, 10:30:21 pm
content: I agree. If I had to choose between Rigol or Siglent for a 200MHz scope I'd choose neither!

author: CPitts
author_rank: Newbie
timestamp: December 29, 2015, 10:59:30 pm
content: Quote from: Mechatrommer on December 29, 2015, 04:18:54 pm$US10K is well above my budget. Trying to stick to a max of ~$US2.5K max, less is better if it kicks the goals.

author: CPitts
author_rank: Newbie
timestamp: December 29, 2015, 11:05:44 pm
content: Great discussion!Coming from many years of PC based stuff (including design) the biggest issue I've always had with sound from a PC is stray noise. Hence trying to avoid it. I've also not seen any tools in the PC space that'll allow me to plug directly into a circuit board or stray wire/pin to get audio signal at _that_ point in the circuit so I can see where the signal IS beginning to change (component isolation).It's those reasons I'd ruled out a soundcard and ruled IN a scope type of device.Have sound cards got THAT much better or am I only now giving people enough info about how I want to check things?

author: CPitts
author_rank: Newbie
timestamp: December 29, 2015, 11:09:36 pm
content: << Admin, feel free to relocate this thread if in wrong area.I did some initial searching and reading of reviews of the scope I was originally looking at (Picoscope 5000 series) but didn't seem to get the info required.>>

author: ADT123
author_rank: Regular Contributor
timestamp: December 29, 2015, 11:13:20 pm
content: Quote from: ataradov on December 29, 2015, 10:10:13 pmIf you read herehttps://www.picotech.com/oscilloscope/5000/flexible-resolution-oscilloscopethe increased resolution is not software averaging - it is achieved by using multiple high resolution ADCs either in parallel for higher resolution or time interleaved for higher speed.As for the SFDR it depends on more than just the ADC used - distortion of the amplifiers for example. 70dB may not match the 96dB theoretical maximum for a 16 bit ADC but its much better than say the 55dB Lecroy manage with their 12 bit scopes (http://cdn.teledynelecroy.com/files/pdf/hro-12bit_datasheet.pdf)

author: ataradov
author_rank: Super Contributor
timestamp: December 29, 2015, 11:19:45 pm
content: Quote from: ADT123 on December 29, 2015, 11:13:20 pmI see a lot of marketing there. How high is "high resolution ADC" and how clear is "crystal-clear display"?Averaging is averaging whether you do it in hardware or software.

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2015, 11:40:05 pm
content: Quote from: ADT123 on December 29, 2015, 11:13:20 pmWelcome to the forum.Quote from: ataradov on December 29, 2015, 11:19:45 pmMarketing is marketing, it is backed up or not by datasheets, teardowns and reviews and has little to do with mature discussion over the merits or not of test equipment.

author: Marco
author_rank: Super Contributor
timestamp: December 29, 2015, 11:56:46 pm
content: Quote from: ataradov on December 29, 2015, 10:10:13 pmSure there are, ADS54J60 for instance.16 bit at 200 MHz is just about thermal noise limited for a 50 Ohm source impedance and 10V range.

author: ataradov
author_rank: Super Contributor
timestamp: December 29, 2015, 11:57:25 pm
content: Quote from: tautech on December 29, 2015, 11:40:05 pmThat is true. I was just pointing out to the OP, not to get seduced by claimed 16-bit resolutions. With 70dB SFDR it probably is not the best for audio applications.Ans as it has been pointed out, good isolated USB audio card will perform much better than nay scope for audio applications.I'd really like to hear Shahriar's (The Signal Path) take on that PicoScope.

author: ataradov
author_rank: Super Contributor
timestamp: December 30, 2015, 12:00:09 am
content: Quote from: Marco on December 29, 2015, 11:56:46 pmGood to know.It is still impractical for this type of application, ADC alone costs more than the entire scopeEdit: Also, with ENOB=11.6, it is hardly a 16-bit ADC.

author: Fungus
author_rank: Super Contributor
timestamp: December 30, 2015, 02:07:53 am
content: Quote from: CPitts on December 29, 2015, 12:20:51 pmNothing to do with me. The author is some guy called "jaxbird".Quote from: CPitts on December 29, 2015, 12:20:51 pmShort version: "Bang per buck"4-channels, 100MHz, 24Mpts memory, loads of goodies for under $400. Nothing else is anywhere close at the moment.

author: rsjsouza
author_rank: Super Contributor
timestamp: December 30, 2015, 04:03:23 am
content: I would also take a look at this other thread:https://www.eevblog.com/forum/testgear/instrument-for-audio-signal-analysis/For clean sinewave generation suitable for THD measurements, perhaps a Keithley 2015 would suit your needs.I have also heard that aKrohn Hite 4402Bsinewave generator is good for audio distortion measurements.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 30, 2015, 06:53:21 am
content: Quote from: CPitts on December 29, 2015, 11:05:44 pmthis applied to anything (PC cards and USB plugged devices), i guess including the $10K lecroy, rigol etc, when..... you have a turned ON PC (or high powered SMPS) right next to the measurement setup... thats why any serious lab measurement setup will bluntly rule out any USB plugged devices..

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2015, 07:51:51 am
content: Quote from: Mechatrommer on December 30, 2015, 06:53:21 amFor that purpuse there are USB isolators or you can use a seperate ADC which is then connected to the PC through optical fibers. A PC and a good audio card really are the best low cost solution for doing work on audio. You maximise the benefit of riding along high volume precision ADC/DAC chip development.

author: CPitts
author_rank: Newbie
timestamp: December 30, 2015, 01:17:59 pm
content: I really like where this discussion has gone and keep it up!I'm trying to avoid having racks of equipment. I've been there and done that stuff with gear before and I don't have an abundant desire to just collect stuff to build up a big wall of dials, buttons and flashing lights.I'm warming to the idea of fibre connected siggen (for EMI control) with a DSP or similar to drive a DAC and ADC with high quality output stage.I do need something at the circuit end where I can put probes against pins and read the signal as it moves through a circuit board or set of components. This WILL include a signal that's post amplification stage so greater than line level. All conversation to date in other threads says this isn't a soundcard.I'm trying to avoid building my own equipment but I can really see the advantage of what blueskull has done and am quite interested in that as an option!I still can't seem to get past the need for a scope to see the signal at pins through a circuit board.There must be something that I'm missing in this part of the process. What's the obvious thing that am I missing here, or is a DSO the right tool in that part of the process?

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2015, 02:52:01 pm
content: In general you work in stages: an oscilloscope can be used to check the shape and presence of a signal. The next stage is to use a different device if you need to measure particular signal properties which an oscilloscope typically can't do. Although more and more gets included into modern DSOs an oscilloscope isn't a very precise instrument. DC vertical accuracy can be as bad as 3% (0.26dB) and at higher frequencies all bets are off.