Oscilloscope Review Checklist - Page 1
Forum section: electronics / testgear

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 12:32:24 am
content: I've been meaning to do this for many years, come up with some kind of standardised checklist when reviewing stuff. Basically so that I don't forget things. Because my usual review method is to just wing it as things come to mind, and sometimes that doesn't work that well.Not a complete list yet by any stretch, but I'd like some input please:https://docs.google.com/spreadsheet/ccc?key=0AnyHtCTsj-bVdFZ4NTY0RFExaUhncXJPUnVNdUpZMGc&usp=sharingObviously I can't test everything in-depth, nor do endless comprisons, or check every range etc, so I really just want to cover the basics you'd expect in a typical full review.

author: pickle9000
author_rank: Super Contributor
timestamp: February 27, 2014, 12:42:34 am
content: I always find serial decoding interesting and of course the cost if it's an option.

author: Omicron
author_rank: Regular Contributor
timestamp: February 27, 2014, 12:49:15 am
content: Probes would be an item I think. The probes that come with the scope and also what other kinds of probes the manufacturer offers. I think this is one area where Tek might still have an advantage. They have some gorgeous probes and a nifty connection system (although it does lock you in to their products).

author: Len
author_rank: Frequent Contributor
timestamp: February 27, 2014, 12:50:54 am
content: Don't forget to ask this guy for advice:https://twitter.com/eevblog/status/438820295713894400/photo/1

author: w2aew
author_rank: Super Contributor
timestamp: February 27, 2014, 12:58:22 am
content: Ease of zooming/panning/navigating long records

author: AG6QR
author_rank: Frequent Contributor
timestamp: February 27, 2014, 01:00:53 am
content: Fan acoustic noise while running might be of interest, but only if it stands out from what's expected. But then again, I suppose, if ANYTHING stands out from what's expected, that deserves a note.The ability to do a deep, one-shot capture to memory and then zoom around the captured results, zooming both horizontally and vertically, may be of interest. How responsive is the zooming, and how much resolution is captured?edit: I see w2aew has a similar note

author: rfbroadband
author_rank: Unknown
timestamp: February 27, 2014, 01:21:24 am
content: - usability of FFT mode- basic digital decoding (I2C, SPI) etc- zooming, panning- trigger events configuration- vertical digital (DSP) filter- math function support- hardware BW reduction (some scopes have a configurable LPF so less noise is sampled by ADC if only lower BW is needed)- ext reference in/out support- mixed signal option (MSO) option available? (and if so, # ch., speed state analysis as well?)- analog BW upgrade via software or hardware?- update rate, waveforms / sec etc- support of multiple waveforms in separate windows for best resolution of each waveform- memory configurations and memory upgrade options- available probes (1:1, 10:1, active, BW)- support for mask testing

author: Rutger
author_rank: Regular Contributor
timestamp: February 27, 2014, 01:23:34 am
content: Boot time, fan noise, ergonomics (button layout)

author: marshallh
author_rank: Unknown
timestamp: February 27, 2014, 01:41:35 am
content: UI responsiveness and useful update rate

author: nowlan
author_rank: Frequent Contributor
timestamp: February 27, 2014, 01:58:07 am
content: How deep the menus are. Are things easy to find.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 02:05:21 am
content: Someone on twitter pointed out this CERN doc on oscilloscope comparisons:http://sl-timing.web.cern.ch/sl-timing/notes/Testoscilloscopes.PDF

author: taemun
author_rank: Regular Contributor
timestamp: February 27, 2014, 02:19:50 am
content: Can the DVM show DCV when the normal front end is on AC coupled mode? (Useful when measuring ripple on top of large DC voltages.)Can the 50R termination be engaged after the AC coupled input?Doing serial decode on a continuous (think I2S) signal, when zoomed out - is it still responsive? (the 3000X baulks at this; it tries to show every white arrow correctly which is a waste of time when there are 20k on screen)Probe look and feel. Are they 10 inches long?

author: AnarchNark
author_rank: Contributor
timestamp: February 27, 2014, 02:23:39 am
content: I really take an interest in the type, or at least the feel of the plastic used for the body and the buttons of a scope.The quality and usability of the handle is important as well. The menu system and its functionality is another really important thing.DON'T FORGET WHETHER OR NOT IT HAS A CLUNKING SWITCH

author: BravoV
author_rank: Super Contributor
timestamp: February 27, 2014, 02:56:13 am
content: Does anyone actually thought about how long does it take for each item ? No, I don't think I'm qualified for that.Just a ball park number, I guess this will help Dave to come with at least a "realistic" time frame for the video shoot at each scope.We're talking about shooting a single video that compares "multiple" scopes at once right Dave ?

author: rfbroadband
author_rank: Unknown
timestamp: February 27, 2014, 03:21:13 am
content: one can spend many hours evaluating scopes ....he can use this feedback to get ideas for additional tests or simply create a basic checklist. No one will expect that every input will be considered for future reviews. That is not realistic.

author: pickle9000
author_rank: Super Contributor
timestamp: February 27, 2014, 03:44:40 am
content: Although not a checklist item it would be nice if you had a couple standard test signals (when applicable). So when you are running through the basics weird stuff would be easier to spot.When I say standard I just mean use the same gear and cable hookup.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 04:11:56 am
content: Quote from: pickle9000 on February 27, 2014, 03:44:40 amI have an oscilloscope demo test board that can generate all kinds of stuff.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 04:14:26 am
content: Quote from: BravoV on February 27, 2014, 02:56:13 amYes, the time and effort it takes to setup tests does determine whether or not I bother doing those.QuoteNo, it's just a checklist for any oscilloscope I review.Reviews may or may not include comparisons of some things with other scopes I have. That's random on the day if I think it's worthwhile showing.I want the list to just be guideline so I don't forget to test something obvious, which almost always happens when I just hit record and wing it.

author: tautech
author_rank: Super Contributor
timestamp: February 27, 2014, 04:55:35 am
content: Describe the full range of ON SCREEN information displayed by default for normal scope use.And make mention of those omitted that one wold expect to be displayed.Of course, they differ as to the price point/intended market.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: February 27, 2014, 08:46:26 am
content: You probably want two lists, one long list you check for strange/wrong behavior and a list to show/talk in the review. (obviously strange/wrong behavior will be added in the review.)

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 27, 2014, 10:02:46 am
content: Trigger modes available, especially for lower end scopes where basics like pulse-width trigger & holdoff can be missing.Range of measurement modes availableHow does memory depth vary with number of channels used/acquisition mode (peak, high-res etc.)

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 27, 2014, 10:08:53 am
content: (Fan) noise is mentioned and already on the list, but could you consider a proper objective dBA measurement?For any device really, not just scopes.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 10:19:01 am
content: Quote from: cybermaus on February 27, 2014, 10:08:53 amNot the easiest thing to do in my lab, too much ambient noise. The measurement has to be done at 1m and are pretty low level.

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 27, 2014, 10:40:57 am
content: Well, if it drops below the 30dBA scale of cheap 'OHL' devices I would already be happy. As doubtful as those devices would be, it's already better then a subjective label of 'fairly noisy' or 'barely noticeable'. (My DS1074Z was way noisier then I had expected from the video reviews)I hardly dare to offer, as you seem to like top-quality products and are ruthless to junk, but I'd be willing to dropship you a budget model. (if you do not have a proper one yet)As to the ambient noise: Just ask the upstairs neighbors to be quiet for a minute

author: jpb
author_rank: Super Contributor
timestamp: February 27, 2014, 10:42:55 am
content: There are often posts on the forum regarding the dc accuracy of scopes. The normal response is that scopes are only 8 bit and around 3% specs but I think some scopes are better than others. I was surprised to find mine was within about 1%.So just as a suggestion, just putting in a couple of dc voltages especially on scopes that give a V readout. If nothing else, I think it gives an indication of the care the manufacturer has put into building the scope.The other thing I didn't see on the list, which may be a bit superseded now, is equivalent time sampling. Assuming that this is done the analogue way it is quite useful for getting a clean version of a repetitive signal (and perhaps looking at jitter - though I'm not sure it adds anything to screen persistence).Edit PS: has anyone suggested BW measurement with your 1Vpp variable frequency source? Of course it would be really nice to have the full frequency response - there was a thread on the forum for people to post the response of their scopes - but that would be too much work.

author: EEVblog
author_rank: Unknown
timestamp: February 27, 2014, 10:51:38 am
content: Quote from: cybermaus on February 27, 2014, 10:40:57 amThanks but I already have one.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: February 27, 2014, 11:05:03 am
content: percentage blind time, in graph representation.

author: AndyC_772
author_rank: Super Contributor
timestamp: February 27, 2014, 11:25:03 am
content: An awful lot of the things which have been mentioned so far are, IMHO, either available from the scope's technical data sheet, or are quite specialised features which apply to a relatively small number of potential viewers.I don't, for example, really want to sit through an experiment that shows a scope sold as 500 MHz actually achieving 542 MHz, based on measuring the rise time of some hand-crafted gadget with a BNC plug on it. I just couldn't care less. If the scope is made by a reputable brand, I'll believe the data sheet. And if it's not, then I won't be using it for anything critical at the edge of its advertised capabilities anyway.The things I want to see from a review are those which aren't readily apparent from just reading the data sheet. For example:- I know a scope with a decent memory can capture a fairly long burst of signal and let me pan and zoom the result, but is it quick, intuitive and easy to do so, or is the UI so sluggish that it's a real chore?- are there any obvious firmware bugs? Often they're a sign of a product that hasn't been properly tested. An unforgivable red flag, IMHO.- do the controls do what you expect them to do? Or do you have to consult the manual or experiment in order to figure out how to zoom / shift / scroll / move / whatever?Focus on the key differentiating features, the cool stuff, the things that work either really well or really badly. For example, on the Rigol DS4000 series, the long memory and waveform recording features are great, and well worth a demo. But the serial decoding is slow, bug ridden, and ultimately much less useful as a debugging aid than it should be. That's worth a demo too.What particularly interests me, as a professional user spending his own money, is how the established high-end brands compare to the cheaper competition. Given that I need a tool which is quick, reliable and accurate, do I still need to buy an Agilent, or R&S, or (maybe) Tektronix? Or does it actually make sense for me to also consider a Rigol, or a Siglent? Are they genuinely comparable in terms of quality, or do they look similar on paper but are still a world apart in use?

author: jpb
author_rank: Super Contributor
timestamp: February 27, 2014, 01:03:57 pm
content: Quote from: AndyC_772 on February 27, 2014, 11:25:03 amI would have thought that frequency response might be a key differentiator that might answer your last point to some extent. I'm thinking of in-band flatness rather than maximum bandwidth.For example the shape of the Tekway scope's response compared with a Tektronix scope shown in this thread :https://www.eevblog.com/forum/testgear/frequency-response-of-your-dso/shows its not a very good scope even though its bandwidth is ok.Unfortunately it is time consuming to produce such plots, and as you say the pulse method only gives an overall bandwidth estimation.Given though that many people on this forum are hobbyists on a tight budget it might be of interest to know that the 70MHz model of a scope actually approaches 100MHz in bandwidth as many of them do.

author: peter.mitchell
author_rank: Super Contributor
timestamp: February 27, 2014, 01:32:50 pm
content: does it have roll mode?

author: MarkL
author_rank: Unknown
timestamp: February 27, 2014, 03:28:42 pm
content: If a scope claims to have protocol decode, I think it should be exercised more heavily than just decoding the few bytes you always see in those lame marketing videos.Load it up with some serial data up to the max of the capture memory and see how the UI behaves and how easy it is to navigate. A convenient source, at least for you Dave, would be the serial demo output on the 3000X. A sample rate of x20 to x100 of the clock is fair (the 3000X does 32kHz for the I2C demo).I'd especially like to see how the new MDO3000 deals with it. We did an eval of the MDO4104B about a year ago and it took 50 seconds to decode a 20M I2C bus sample (and 200 seconds for 4 buses). I like Tek scopes a lot, but if they're going to charge a premium for all this decode stuff it needs to be usable as such. I hope they improved it on the MDO3000.

author: TMM
author_rank: Frequent Contributor
timestamp: February 27, 2014, 03:39:08 pm
content: One thing i look for is whether the FFT function works on just what is shown on the screen, or the entire memory depth.

author: AndyC_772
author_rank: Super Contributor
timestamp: February 27, 2014, 04:36:57 pm
content: Quote from: jpb on February 27, 2014, 01:03:57 pmNot really. It's a rare situation indeed where I care about a small difference in amplitude response. I'm much more likely to be interested in a time difference between two signals, and much, much more likely again to be interested in checking the qualitative (not quantitative) characteristics of something.I can count the number of times I've used my scope to measure the precise amplitude of a fast (hundreds of MHz) signal on the fingers of one foot. Today I'm using it to do serial decoding on an SPI interface. Yesterday I was showing the analogue output of a sensor in roll mode at 1 sec/div, and my next job is likely to be checking the functionality of a long range wired bus operating in the kHz range.I have a 500 MHz scope not because I care about amplitude flatness, but because at the time I bought it I was doing optical research which demanded a fast time base and the ability to measure short time intervals accurately. Even then, though, that was only one specific use, and more often than not I was still using it to probe dc-dc converters and RS232 ports.QuoteCan you think of any real, practical application in which such a small difference in bandwidth makes the difference between a scope which is useful and one which isn't? I'm afraid I'm struggling to come up with anything.

author: jpb
author_rank: Super Contributor
timestamp: February 27, 2014, 06:43:36 pm
content: Quote from: AndyC_772 on February 27, 2014, 04:36:57 pmI guess looking at square waves at around 20-30MHz range. But I was more thinking that the advice is often to get a 100MHz scope at a minimum, but if the 70MHz scope is shown to be close to it then the buyer on a budget can save a bit of cash - though now-a-days 100MHz scopes are available in budget models anyway.

author: Deckert
author_rank: Regular Contributor
timestamp: March 01, 2014, 01:47:51 am
content: Hi,I posted this list to mjlorton at some point, might be useful here as well.- How quickly does the scope return to zero-line after it has triggered (or been given an input voltage above 0V)? The cheaps scopes seem to lag here, but I've seen the Agilents lag on this as well.- handling of a single fast pulse (to check/see rise time and test trigger accuracy, not frequency response testing)- feed it a nominally high frequenxy (i.e. 50MHz, 100MHz) and check waveform stability and trigger position (does it trigger late?)- feed it a pulse, zoom in on the pulse (does it loose resolution?)- noise floor test- responsiveness (vert and horiz controls must be reasonably responsive and not lag)- low-voltage and high-voltage trigger (does it still trigger reliably at the low end and high-end of the pulse/wave)- scope user interface should be feature complete+ vernier controls on vertical scale (pushable adjustment knobs)+ center-function on pushable position knobs+ Menu on/off button (if the side menu can be removed)+ Roll/scan mode at slow time bases+ quick access to all functions and status displays+ single button-press for saving of screen captures+ acceleration control on all knobs is a must(i.e. slow turns result in small steps, fast turns in large steps)+ has to be responsive, did I mention it has to be responsive?- scope trigger system should be excellent+ scope triggers at the set trigger point (and not later or sooner)+ Auto-trigger mode to initially find signals+ trigger on both up, down, up-and-down and alternate channels+ array of trigger options for pulses, edges and slopes- cursor control (actually a user interface feature)+ manual and tracking controls for cursors- zoom mode+ inspection of a frozen/stopped signal by zooming it+ fast sample rate in deep memory modes (to facilitate better zooming)- measurment and acquisition+ the usual array of measurments on the wave (or waves)+ hardware freq. counter (can't figure out why Agilent left this one out)+ vector and dot mode (although need for dot mode is likely replaced by graded intensity display on eg. the Agilent)+ fast updating XY-mode (eg. must be able to at least show Youscope)- Solid build quality, but not too heavy, should not slide away when pressing buttons- Quiet fan - cannot overstate the importance of this--deckert