HP 54610 "500 MHz"  Scope - An Useless 2 MHz Sampling Scope? - Page 1
Forum section: electronics / testgear

author: niconiconi
author_rank: Frequent Contributor
timestamp: September 02, 2020, 10:26:51 pm
content: While hunting for test equipment on the second-hand markets today, I noticed a HP 54610 digital oscilloscope with "500 MHz" bandwidth. At first glance, It sounds like an adequate scope for testing some 100 MHz digital circuits at the lowest price (an almost nonexistent memory depth, but I can tolerate that).The problem is, I noticed its performance is very unusual. From the specs, it has deceptively amazing performance headline,QuoteHowever,QuoteDoes it mean that in practice, the HP 54610 scope is effectively a sampling oscilloscope that's only usable on periodic signals, similar to those old Tektronix sampling heads? And its true, real time bandwidth is only 2 MHz? Well, I guess it still has its uses like checking signal integrity on clocks (and on data with a test pattern) and analog measurements. But its capabilities are just too limited - nearly useless in digital electronics for all other tasks to the point where even the cheapest 100 MHz real-time DSO is better. It cannot even debug a 6502 computer...Is my understanding correct? Back in the day, what were the jobs that scopes like this one designed to do?

author: Fungus
author_rank: Super Contributor
timestamp: September 02, 2020, 10:37:52 pm
content: Back in the day, stuff like that was very expensive/difficult.Result: Analog 'scopes with a few very limited storage abilities.

author: niconiconi
author_rank: Frequent Contributor
timestamp: September 02, 2020, 10:44:46 pm
content: Quote from: Fungus on September 02, 2020, 10:37:52 pmI'm seriously considering to get an analog oscilloscope and setting up long-time exposure on a DSLR camera to get eye diagrams out of my 100 MHz interface. On my zero-budget hobby project, it seems to be the cheapest way to get the job done.

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2020, 03:01:25 am
content: Quote from: niconiconi on September 02, 2020, 10:26:51 pmThe 2 and 1 MHz bandwidth ratings come from HP conservatively rating their maximum bandwidth at 10 sample points per cycle, but the full vertical bandwidth is still available at those slow sample rates.QuoteDSOs like that were intended for exactly those types of applications where high single shot sample rates were not required. This includes things like semiconductor testing where multiple acquisitions could be made to support equivalent time sampling.Quote20 MS/s is actually sufficient for a lot of general purpose design work, as anybody who has used a Tektronix 2230 can attest to. Personally I think a bigger limitation of the HP 54610 series is the lack of peak detection, which the Tektronix 2230 supports down to 100 nanoseconds.

author: dzseki
author_rank: Frequent Contributor
timestamp: September 03, 2020, 05:44:44 am
content: I had the 54503 which is the older version of this concept, it was very much usable. In fact it behaves very much like an analog scope in terms of visualisation of random glitches and "memory depth" -all you have is what you see on the screen.I mean you have little hope in catching a random glitch on a pulse train on an analog scope -the phosphor will simply not light up.With modern DSO it is an addictive habbit that you record a single pulse and do whatever on it in STOP mode, now obviously this work very limited with this HP scope due to the low memory. But again even an analog storage scope can't do this better either.My biggest concern with the 54503 was is that it had rather low waveform update rate whenever any automatic measurement was on, if the measurement was off it was OK. But I'm farily sure that the 54610 should have more "modern" hardware, so I don't know if it acts the same.

author: 0culus
author_rank: Super Contributor
timestamp: September 03, 2020, 05:51:04 am
content: Quote from: dzseki on September 03, 2020, 05:44:44 amMostly true, but there were ways of catching things. Variable persistence and storage tubes, for one thing. The former is often emulated on digital scopes. Oscilloscope cameras were also a thing. None of them are as good for single shot events as a modern DSO though. Storage CRTs, especially, generally suck and weren't very good when they were new, let alone in 2020.I have a single one (an HP 1727A) and I use the variable persistence all the time, but never bother with the storage function. It will do single shot captures but it's pretty much a shot in the dark.

author: dzseki
author_rank: Frequent Contributor
timestamp: September 03, 2020, 06:19:40 am
content: Quote from: 0culus on September 03, 2020, 05:51:04 amThe big deal with the HP 1727A was its high writing speed in storage mode (at least HP hyped this), and as you say even this made hard for capturing fast single events. On a generic analog storage tube the writing speed was usualy so low that it couldn't record anything close to its rated bandwidth anyway.

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2020, 06:51:03 am
content: Quote from: niconiconi on September 02, 2020, 10:44:46 pmEye diagrams are only useful with repetitive waveforms. I would expect that you can plot eye diagrams on the 54610, if you set it to infinite persistance.OTOH, using the available tools to achieve the desired results cheaply is good engineering practice. See my .sig!

author: vk6zgo
author_rank: Super Contributor
timestamp: September 03, 2020, 08:09:44 am
content: Quote from: niconiconi on September 02, 2020, 10:26:51 pmCertainly not the "instrument of choice" for anything much analog other than looking at Sinewaves up to UHF, where it is probably very good, indeed.Equivalent time sampling doesn't work well for such delights as looking at analog video, or for searching for low frequency hum on pulse trains with fairly high frequency components.

author: chris_leyson
author_rank: Super Contributor
timestamp: September 03, 2020, 09:24:20 am
content: QuoteYes. It's only good for repetitive signals and it's real time bandwidth is 1MHz for two channels and 2MHz single channel. I picked up a 54610B going really cheap. It's OK for audio work or some switched mode supplies but not much else apart from looking at VHF UHF sinewaves. Useless for video work and any sort of digital debugging.

author: dzseki
author_rank: Frequent Contributor
timestamp: September 03, 2020, 09:43:27 am
content: Quote from: chris_leyson on September 03, 2020, 09:24:20 amAs was said before the frontend of the scope is fully capabe up to 500MHz, it is only the 20MS/s sampling that limits your perceived bandwidth, that's all.Mind you I've used my HP 54503 scope to analyse analog video signals in excess of 200MHz pixel clock, you just have to setup your trigger and test patterns properly and you'll quickly find that you are in fact looking at a repetitive signals

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2020, 09:45:57 am
content: Quote from: chris_leyson on September 03, 2020, 09:24:20 amIf you are debugging digital signals, use a digital domain tool such as a logic analyser or printf().If you are debugging analogue waveforms that are intended to be interpreted as digital signals, then use a an analogue domain tool such as a scope to assure signal integrity. Any scope with an adequate bandwidth (usually >=100MHz) is suitable for that.See the aphorism in my .sig.

author: niconiconi
author_rank: Frequent Contributor
timestamp: September 03, 2020, 11:44:57 am
content: Quote from: tggzzz on September 03, 2020, 06:51:03 amI still cannot understand the operation of this oscilloscope, never used any sampling oscilloscope before. Elaboration is appreciated.What does it mean by "eye diagrams are only useful with repetitive waveforms"? In this thread, I always used the word "periodic", did your choice of the word "repetitive" convey a different meaning here? For example, If I have a 1-bit serial interface that outputs a random bit per clock cycle, I won't call the signal on the data line a "periodic signal“ since the cycle of the bitstream is unpredictable. But is it "repetitive" to you?And I previously thought capturing a non-periodic signal is impossible on a sampling scope - But actually the signal doesn't have to be periodic, just be "repetitive" is enough, the bitstream itself doesn't have to be periodic, all we need is repetitive high-to-low and low-to-high transitions - is it the correct understanding?

author: dzseki
author_rank: Frequent Contributor
timestamp: September 03, 2020, 12:15:55 pm
content: Take it simple, this scope can sample at 20MS/s at any settings. BUT if the signal is repetitive (= the signal has the same shape after the trigger event all the time), it shifts the sampling with random (small) intervals against the trigger event, therefore after sampling through many-many triggers it will yield a densely sampled waveform.An 1 bit random pulse train is not like this, but if your random pulse train have a certain bit pattern frame for example, and you manage to trigger to that frame only it will appear to be repetitive to the scope even though the rest is not repetitive.

author: 2N3055
author_rank: Super Contributor
timestamp: September 03, 2020, 12:41:28 pm
content: You can build eye pattern with it though with full 500MHz bandwith. You just have to let it run while running PRBS sequence (or full sequential sequence) ...

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2020, 01:21:14 pm
content: Quote from: niconiconi on September 03, 2020, 11:44:57 amThere are many sources describing that. I'm not going to poorly summarise them.QuoteYou have omitted the context, and I'm not going to bother to search for it.I suggest you look at an example eye diagram (use google), that will clear up a lot of your confusion.QuoteYou need to understand the Nyquist-Shannon sampling theorem. Google is your friend.

author: niconiconi
author_rank: Frequent Contributor
timestamp: September 03, 2020, 10:43:20 pm
content: Quote from: tggzzz on September 03, 2020, 01:21:14 pmThanks for the clarification. I confirmed that my original understanding of both a sampling oscilloscope and the Nyquist-Shannon sampling theorem is correct, no need to Google.When you said "eye diagrams are only useful with repetitive waveforms", you meant "it's only possible to do an eye diagram on a sampling oscilloscope with a repetitive test pattern", I originally misunderstood it to mean either "all eye diagrams, including those captured on a real-time oscilloscope are only possible with a repetitive waveform" or "on a sampling oscilloscope, it's possible to get an eye diagram without a repetitive test pattern", and seriously confused, and felt I no longer understand eye diagrams nor sampling oscilloscope. It turned out I was overthinking the problem.

author: David Hess
author_rank: Super Contributor
timestamp: September 04, 2020, 04:38:59 am
content: Quote from: niconiconi on September 03, 2020, 11:44:57 amIt is not that simple, and the HP 54610 does not qualify as a sampling oscilloscope any more than a Tektronix 2230 with its 20 MS/s sample rate does. At a fundamental level, sampling oscilloscopes are a different type of instrument.Both low and high sample rates are sufficient for capturing the histogram of a signal which is what an eye diagram is.