EEV ScopeBench 0.1 - Page 1
Forum section: electronics / testgear

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 23, 2013, 05:39:08 am
content: While working on a project I somehow had to think about all the various discussions regarding scopes, waveforms, what's a good beginner scope and such, and I thought maybe what's needed is a standardized benchmark, something like a '3Dmark" for scopes, an 'EEV ScopeBench'?The idea is that we define a set of standardized tests any scope can undergo and which can be performed easily even with simpler test gear, and then create a thread where the results for the various scopes are collected. Tests would include waveform rate tests in various modes (single/multi channel, persistence, equivalent time sampling etc), real bandwith tests (albeit this would be problematic as it requires a suitable signal generator), and various other parameters that we could define. The result would not be a single number but a set of data that can be easily compared with the results from other scopes.We could also define optional tests which tests advanced features on certain scope models.This would also help people with creating useful video reviews of scopes as it could people give an idea about what to test instead of just feeding a sine wave to a scope and saying 'it rocks!'.I admit it's not a totally serious idea, but it could be fun nevertheless.Any thoughts?

author: quarros
author_rank: Regular Contributor
timestamp: May 23, 2013, 08:40:35 am
content: I don´t want to sound overly pessimistic, but what about the unavoidable discrepancy between the "ScopeBench's"? Because even the test equipments that roll from the same manufacturing line, with the same manufacturing process. Needs calibration.I just don't see what magic can we use to conjure up and publish a schematic/gerber that doges this problem and allows hobbyists to make it on their own to the same characteristics.But I would be delighted if I'm wrong about this, because the idea is great

author: jpb
author_rank: Super Contributor
timestamp: May 23, 2013, 09:00:07 am
content: I like the idea but you'd need to have flexibility to allow for different designs for different scopes.For example I've just been having fun getting waveforms/sec figures for my WaveJet. Here there is a major difference at some time bases between having lines on during capture and having them off (by a factor of 20 times!) but the scope is showing 1,024 x 500 point captures at once which is different from persistence mode as the captures change as new ones are added and the oldest ones dropped. The point is that because you're seeing 500k points you don't really need lines on and if you have lines on it has to plot them 1024 times so it is not surprising that it slows down.It would be unfair to make lines on a condition on the EEV ScopeBench as it would penalise the WaveJet vs say an Agilent which keeps no history and is designed for lines on anyway (I think - I don't know the Agilent very well as I don't have one). But on a scope that keeps only one wave at a time it might need lines on to be able to see the curve clearly.Manufacturers tend to do comparisons based on conditions that suit their scope and don't suit others. EEV ScopeBench may be an opportunity to balance things up by allowing each scope to be set to the optimum conditions only constrained by say timebase setting and the requirement that the screen must have a useful display.There was a separate thread on actual bandwidths which perhaps could be linked in. The problem with actual bandwidth is that it a.) requires good equipment to measure and b.) it is not really a single measurement. For instance the better scopes have nice flat pass bands whilst some of the cheaper scopes have quite high bandwidth but massive ripple within the pass band.An alternative single number might be the rise time measured using the Jim William's pulse generator as a lot of people have built one of these, particularly using Vince's kit.

author: EEVblog
author_rank: Unknown
timestamp: May 23, 2013, 09:17:26 am
content: What's really needed is the likes of one of the "demo boards" available for scope, that generate a whole host of standard signals.I have a Tektronix MDO4000 demo board (see attached)And Rigol are supposed ot be sending me their 6000 series demo board, but I'm not holding my breath.http://www.batronix.com/pdf/Rigol/UserGuide/DS6000DemoBoard_UserGuide_EN.pdfhttp://www.batronix.com/php/index.php?Cookie=Set&__utma=264830992.877665616.1369300585.1369300585.1369300585.1&__utmb=264830992.1.10.1369300585&__utmc=264830992&__utmz=264830992.1369300585.1.1.utmcsr%3Dgoogle%7Cutmccn%3D%28organic%29%7Cutmcmd%3Dorganic%7Cutmctr%3D%28not+provided%29&cmd=find&loc=en&image2_x=-1203&image2_y=-56&query=ds6000+demoAs an aside: I just did a simple google search and found this "Tektronix Confidential" sales documenthttps://www1.elfa.se/data1/wwwroot/assets/datasheets/48W-28883-0_MDO4000_ENG.pdf

author: jpb
author_rank: Super Contributor
timestamp: May 23, 2013, 09:38:28 am
content: Quote from: EEVblog on May 23, 2013, 09:17:26 amThough these demo boards look fun, I'd be reluctant to pay £200 for a series of one-off tests on a scope I already own. At the end of the day it is a bit like running benchmarks on a pc/workstation when I get a new one I enjoy seeing what it scores but after that I don't run them again. The demo board is a bit more useful as it produces signals that might be useful for other tests on circuits but they are ESD sensitive and not enclosed so aren't really designed as test gear.Perhaps a pass-it-round arrangement could be made but it would be complicated. Perhaps the simplest way of doing this would be for a group of people to agree a sell-it on price.First person buys new at £200, the next person agrees in advance to buy it for £180 and so on and the 10th person buys it for just £20 and gets to keep it but has a board that has already been used several times and has to wait the longest. Maybe it would be fairer to have a higher final price and a smaller drop in-between.The other thing is that they are set up for particular scopes. For instance the Rigol one generates glitches of just the right duration and frequency to show off the Rigol scope's wfms/sec and presumably other manufacturers are the same. So it would be too frequent for a Agilent 3000X series and too infrequent for say a Hameg (or WaveJet).

author: EEVblog
author_rank: Unknown
timestamp: May 23, 2013, 09:56:10 am
content: Quote from: jpb on May 23, 2013, 09:38:28 amYes. What I was getting at is somone needs to create a cheap open source one.QuoteBut that's the whole idea, showing the differences. It's common for example for Agilent sales people use a Tek or Lecroy demo board for example to "show up" the competition with their own demo board.There is probably a need for a proper industry "benchmark board" that all manufacturers could use to advertise the capabilities of their scopes.

author: jpb
author_rank: Super Contributor
timestamp: May 23, 2013, 10:07:46 am
content: Quote from: EEVblog on May 23, 2013, 09:56:10 amPerhaps rather than produce open-source hardware (demo board), an existing fpga or microcontroller board could be programmed, perhaps even a sound card or video card , I came across a paper a while back where people had programmed a cheap video card to produce useful test signals - see the link:http://indico.cern.ch/getFile.py/access?contribId=11&sessionId=30&resId=0&materialId=paper&confId=49682

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 23, 2013, 02:39:50 pm
content: Quote from: quarros on May 23, 2013, 08:40:35 amThis is true but ultimately doesn't matter, as the deviations between different exemplars of a certain scope should be negligible (or at least one of the scopes is defect or the manufacturer has no quality control).QuoteNo need for magic, just doing what people are already doing in a more standardized, unified way which would make comparison of the various performance parameters much easier.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 23, 2013, 02:42:35 pm
content: Quote from: EEVblog on May 23, 2013, 09:17:26 amI agree that a 'demo board' is probably a good thing for people like you who review scopes regularly, but it certainly isn't a viable alternative for occasional reviewers.In addition, the issue is not the signal generation, the idea is about standardizing the test procedures and collecting the results in one place.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: May 23, 2013, 02:47:41 pm
content: Quote from: jpb on May 23, 2013, 09:38:28 amAs the idea was more about how to test and not about the signal source I think demo boards completely miss the point, and they certainly are no viable way to get some basic performance parameters from a scope.

author: kfitch42
author_rank: Frequent Contributor
timestamp: May 23, 2013, 04:51:23 pm
content: So, if we were to try to take this seriously, what features/requirements/constraints1a) Is this intended to be a product like uCurrent or something you could pick up from Seeed/sparkfun... (and at what price $50, $100, $300 ?)1b) Or more a collection of schematics of circuits interested hobbyists could build each from $5-10 of parts from digikey/mouser...2) How is this different from a sig gen? At the very least, I assume, it would need a simple sig gen (square, sine,)3) Would this be about measuring or comparing3a) Should it spit out something like "1234 Waveforms/Sec, 4321ps risetime, 123Mhz bandwidth"3b) Or should it just generate a [fixed,adjustable] signal with a [glitch, fast risetime, ...] and you could compare how easy it is to diagnose/see with different scopes?4) What is out there right now to accomplish similar goals4a) Demo boards (as have been mentioned)4b) Cheap ebay DDS/siggen kits (http://www.ebay.com/sch/i.html?_nkw=dds)4c) Ebay oscilloscope tester (http://www.ebay.com/itm/130864417080)4d) Jim williams pulser () or W2AEW's Schmitt trigger circuit ()4e) The dueling threads going on right now about measuring waveforms/sec:https://www.eevblog.com/forum/testgear/a-simple-technique-to-measure-waveform-update-rates-on-dsos-with-no-trigger-out/andhttps://www.eevblog.com/forum/testgear/measuring-the-waveforms-per-sec-for-wavejet-without-a-trigger-out-counter-etc/