Scope speed for digital - Page 1
Forum section: electronics / testgear

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 03, 2021, 03:17:57 pm
content: Hi, can you measure with a 40MHz scope frame accurate a 40MHz chip pin output ?thanks

author: Kean
author_rank: Unknown
timestamp: October 03, 2021, 03:35:57 pm
content: No.Read thishttps://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 03, 2021, 03:47:46 pm
content: Then i need at least 200 MHz for my DSPIC.

author: Fungus
author_rank: Super Contributor
timestamp: October 03, 2021, 03:53:44 pm
content: Quote from: Jan Audio on October 03, 2021, 03:17:57 pmNo.A square wave is sum of many sine waves (harmonics). With a 40Mhz 'scope you can only see thefirstsine wave clearly. All the other harmonics will be missing (or very attenuated).Result: It will look like a distorted sine wave on screen, not a square wave.https://en.wikipedia.org/wiki/Square_wave#/media/File:Fourier_series_for_square_wave.gif

author: Kean
author_rank: Unknown
timestamp: October 03, 2021, 04:21:04 pm
content: Quote from: Jan Audio on October 03, 2021, 03:47:46 pmDid you read all of the blog post I linked?Will your DSPIC only be outputting 50% duty cycle square waves?Edit: You probably need to think about how "accurate" you need your measurements to be.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 03, 2021, 04:47:02 pm
content: Every frame counts, my fastest chip i use is 40 MHz, i also have 32 bit chip at 48 MHz.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 03, 2021, 04:53:04 pm
content: Quote from: Kean on October 03, 2021, 04:21:04 pmAnd tell us what it is you want to measure?A digital io pin being controlled by the dspic or a i2s data clock pair sending data to a dac, or receiving from an adc, etc.

author: bdunham7
author_rank: Super Contributor
timestamp: October 03, 2021, 05:59:14 pm
content: Quote from: Jan Audio on October 03, 2021, 03:17:57 pmDo you just want to see if it is there or not, do you need to decode it, or are you wanting to see transitions and timing for troubleshooting?For the first, sure a 40MHz BW scope will show you 'something'. A 200MHz scope with <2ns rise and 1GSa/s will give you a pretty good picture and allow accurate decoding, a 350MHz scope with <1ns rise time and 2GSa/s should show things crisply enough for almost any purpose.

author: rob77
author_rank: Super Contributor
timestamp: October 03, 2021, 06:00:37 pm
content: why would anyone need to accurately scope a digital signal at 40MHz ? for clock you want to know if it is there or not, and in that case it doesn't matter how does it look like on a screen (distorted sine is good enough). also during troubleshooting digital stuff the scope is used to determine if there is some activity or not , and again distortion is not a problem. to see a phase shift between 2 signals again not a problem. for more serious troubleshooting you need a logic analyzer... i'm a bit curious what the measurement in question would be

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 06:45:50 pm
content: Quote from: rob77 on October 03, 2021, 06:00:37 pmOscilloscopes don't observe digital signals - they observe analogue waveforms that a receiver mayinterpretas digital signals.Oscilloscopes allow you to see whether the analogue waveforms will be correctly interpreted as digital signals - this is termed "assuring signal integrity". Many features can be observed and measured using a variety of techniques, especially setup and hold times, voltage levels and under/overshoot, and eye diagrams.Once the signal integrity is correct, it is often beneficial to flip into the digital domain and use a logic analyser and printf() statements to observe digital signals.

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 06:48:40 pm
content: Quote from: Kean on October 03, 2021, 04:21:04 pmIt looks like he didn't understand even the first paragraph, which containsQuote

author: Fungus
author_rank: Super Contributor
timestamp: October 03, 2021, 07:20:09 pm
content: Quote from: tggzzz on October 03, 2021, 06:48:40 pmLast time I checked 5 times 40MHz was 200MHz.ie. He read it.

author: nctnico
author_rank: Super Contributor
timestamp: October 03, 2021, 07:34:44 pm
content: Quote from: Kean on October 03, 2021, 03:35:57 pmThis article actually is pretty bad as it focusses on high frequency content of edges and not the functional aspect of a signal. As usual the answer to how much bandwidth you need is: 'it depends'. For most measurements you will want to check whether the digital signal has the proper levels and meets timing. For that you will want to see at least the first harmonic of a square-ish waveform to get a ball-park idea. The first harmonic of a square wave is 3 times the fundamental frequency. For more detail you will want the 2nd harmonic as well which is at 5 times the fundamental frequency.For looking at signal integrity issues you'll need more bandwidth (or better put: risetime) but in a sane circuit it helps to simply slow the signals down using a series resistor at the source.

author: bdunham7
author_rank: Super Contributor
timestamp: October 03, 2021, 07:51:19 pm
content: Quote from: nctnico on October 03, 2021, 07:34:44 pmYes, it had a sort of half-baked bullshit smell to it...A "1% duty cycle" is not a very relevant example. A clocked data signal with a 25ns period is not going to have 250ps pulses to worry about, nor is it likely to have <1ns rise times. What it may have are subharmonics below the fundamental....all depending on the coding used.

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 08:24:09 pm
content: Quote from: nctnico on October 03, 2021, 07:34:44 pmI thought the article was pretty clear on the what it was trying to communicate.. It wasn't about the "functional aspect of signals" (whatever that is). Even the title states the rise time is the important parameter!But your statement is wrong in two respects.The second harmonic of a fundamental frequency f is 2f. A square wave contains only odd harmonics, at 3f, 5f etc. The amplitudes of the even harmonics is zero. Your statement indicates you misunderstand that.Mor importantly, your statement implies that given a 1kHz CMOS clock signal with a 50% dry cycle, for signal integrity purposes you only need to consider up to 5kHz. That is completely wrong.

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 08:30:29 pm
content: Quote from: bdunham7 on October 03, 2021, 07:51:19 pmThe article was clear in the title and description that the particular parameters were not representative of all signals!

author: bdunham7
author_rank: Super Contributor
timestamp: October 03, 2021, 08:51:54 pm
content: Quote from: tggzzz on October 03, 2021, 08:30:29 pmOne can simplify and generalize to the point where although even though everything that is said is correct, it is meaningless in the real world because it doesn't apply to actual examples. IMO the article raised needless questions rather than providing useful answers. As I said, BW=5X clock is good enough a lot of the time, 10X clock is almost perfect, assuming 5X BW sampling rate. Show me an example where that doesn't work (there probably is one) and maybe I'll learn something.I think all of us here understand the fundamentals involved here, it's just a matter of practical usage. I probably have the least experience here because I only run into these issues in the context of repairing stuff. However, I have yet to see adatasignal system that was itself designed to accurately handle signals with bandwidth of 100X (or 99X) the clock rate. If you have clock signal doing something else that requires precision and rise times much smaller than the clock rate, then you do have a different case.

author: 2N3055
author_rank: Super Contributor
timestamp: October 03, 2021, 09:07:23 pm
content: Hi Jan,please could you explain what do you try to measure. Jitter ? Signal integrity (eye, over/under shoots, resonances?). It is important.If you want to see and measurefast edgesquarewave signal withgood fidelity, you need 10x faster scope than your squarewave repetition rate.So for 40 MHz squarewave, 400 MHz scope. That is a good rule of thumb.If you want to see signal reasonably well 5x might be enough.. It will allow you to roughly see where rise/fall edges are corelated to each other. Top of the pulses and over/undershoots will not be reliable if signal has fast edges...As others said ,how fast edges on that squarewave aredefines how fast scope you need. Fast edges "hide very high frequencies inside" (that is very, very simplified view on frequency content of signals). Faster the edges, higher frequencies "hide inside". Despite repetition frequency might be 1 MHz, you might need 1 GHz scope to see all the details of the signal if edges are very fast..If you have 10 MHz clock with 5 ns rise/fall time, even 100MHz scope will show it nicely. Because 100 MHz scope will have it's internal limit of about 3-3,5 ns risetime.So it is faster than the edge you're looking. Make note that 10MHz signal with 5 ns edges will allready look slightly trapezoidal. It won't be perfect squarewave.And that is done deliberately very often, to make system more robust and EMC compliant.FPGA chips (and many other logic ICs) have settings to set rise/fall times, because it is beneficial to run edges as slow as possible, because they run cleaner that way and EMC and layout is less critical. Less ringing, less crosstalk...DsPIC has different rise/fall time specifications for different pins and ports.You must look in a datasheet and look at what is specified rise/fall times for that port.You scope has to have faster risetime than this. Factor of twice as fast is already less than 3% error measuring rise times ...

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 10:24:58 pm
content: Quote from: bdunham7 on October 03, 2021, 08:51:54 pmThat explains a lot; thank's for the elucidation.My experience is in designing circuits. There you have a visceral understanding of setup and hold times, and how easy it is to violate them, and how signal integrity problems lead to intermittent failures.QuoteIf you restrict your thinking to special cases then of course you can be right. But...If you have a modern CMOS devices with, say, a 32768Hz clock, then the transitions will bemuchfaster than the clock rate. Consider a simple D-flip flop such as a 74lvc1g74 clocked by that signal. If there is a 2.5ns glitch on that clock, then it will malfunction. It has a 1ns hold time; if the other circuits don't meet that, then it will malfunction. To rub the point home, those times are less than 0.01% of the clock period!Consider a 1pps output from a GPSDO or GPS or rubidium source. If that has a risetime commensurate with 1Hz then it would be completely useless. And nobody cares about the pulse width; only the leading edge is important.

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 10:34:41 pm
content: Quote from: 2N3055 on October 03, 2021, 09:07:23 pmThe first rule of thumb is to know the limitations of a rule of thumbhttps://www.edn.com/rules-of-thumb-0-using-rules-of-thumb-wisely/So, what bandwidth to you recommend for a 1pps/1Hz clock output from a GPS receiver?QuoteFor a given logic family, even in a 1pps circuit, the setup and hold times (and edge times) will be the same as in a 100MHz circuit.QuoteAs you obliquely indicate, the only parameter of relevance is the risetime; the period is irrelevant.

author: 2N3055
author_rank: Super Contributor
timestamp: October 03, 2021, 11:08:32 pm
content: Quote from: tggzzz on October 03, 2021, 10:34:41 pmYou are missing the point. OP speaks about 40 MHz signal....We are talking at looking at squarewaves. That is a pulse signal that has 50% duty cycle.Also we are talking about practical limits to see whether such signal looks lik a reasonable square wave and have reasonably well formed edges compared to it's repetition rate... It is all there where I wrote it.. Including caveat that if you need to look at the very fast edge on (comparatively) slow repetition rate signal you need to be concerned with rise/fall rate only...So what I wrote wrong? And my rule of thumb holds well for average digital signal..Talking about 1 PPs signal is edge case not being relevant here..And answer is I don't know, which GPS receiver it is, so we can look in a datasheet.?

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 11:26:25 pm
content: Quote from: 2N3055 on October 03, 2021, 11:08:32 pmYou are talking about those, but the OP has not characterised his signal as a square wave.QuoteWhat is "reasonable" depends on the logic families; the OP has given no indication of what they are. There's a lot of difference between 4000 series CMOS, 74lvc CMOS, FPGA i/o, high speed serial links, etc.QuoteThere is no such thing as an "average digital signal". Some are regular, some irregular, some random, and some single-shot signals that are expected to never be active.QuoteIt is a deliberately extreme (but real) example to force people away from thinking a period/frequency is relevant.QuoteThat's a fundamental property of a 1pps output signal fromanyGPS receiver.

author: bdunham7
author_rank: Super Contributor
timestamp: October 03, 2021, 11:28:52 pm
content: Quote from: 2N3055 on October 03, 2021, 11:08:32 pmI'm not sure we can bank on them being exactly 'square', but my general thought is that a protocol forencoding and transmitting digital datais going to be optimized to take maximum advantage of the analog bandwidth available--or conversely, use the minimum bandwidth for a specified data rate. You can push the data rate vs. the clock rate, like DDR, but I don't think you are going to see required rise times at 1/100 X clock in a data transmission protocol.

author: tggzzz
author_rank: Super Contributor
timestamp: October 03, 2021, 11:41:18 pm
content: Quote from: bdunham7 on October 03, 2021, 11:28:52 pmConsider a 9600b/s UART data transmission protocol implemented with any modern logic. (Or 300b/s if you insist!) While the transition timecouldbe reduced to 10s of µs, in practice it won't be.

author: Kean
author_rank: Unknown
timestamp: October 04, 2021, 12:04:04 am
content: Quote from: Fungus on October 03, 2021, 07:20:09 pmApparently you read it about as well as OP did. The first paragraph begins withQuoteIt isn't a perfect article about measurement bandwidth requirements, but the point of suggesting the OP read it was to get them to think about what they are actually trying to measure.The simple answer to OP's question was, no a 40MHz scope is not sufficient. The longer answer (i.e. what he actually needs) is, it depends. It depends on signal risetime, but also on what he expects/wants to be able to measure. OP didn't ask about protocol decoding, so I was assuming signal integrity was top of mind.

author: joeqsmith
author_rank: Super Contributor
timestamp: October 04, 2021, 01:26:59 am
content: QuoteBack in the dark ages of analog...

author: rob77
author_rank: Super Contributor
timestamp: October 04, 2021, 01:37:05 am
content: Quote from: tggzzz on October 03, 2021, 06:45:50 pmi understand your urge to explain everything to everyone but what's your point here ?oscilloscope observe whatever you feed into the input.. the definition of "digital" signal is basically just applying some boundaries/envelope.OP was talking about measuring a signal coming from a "40MHz chip". in wast majority of cases you don't have to scope a digital signal for integrity coming from a chip (like you don't check ball bearings for roundness) , hence my post explaining the non-importance of the bandwidth as long as the scope can display the signal in some form.furthermore signal coming from a "40MHz chip" and "32bit 48MHz chip" doesn't necessarily mean it's a 40MHz or 48MHz square wave... hence my curiosity towards the measurement in question. the OP's description of "chips" would suggest a MCU of some kind and the highest frequency is the clock in that case

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 05:23:02 am
content: Quote from: rob77 on October 04, 2021, 01:37:05 amInside the chip this will be true, but with most modern MCU's the outside clock will be way less. STM32 devices mostly use an 8MHz or 25MHz external crystal (oscillator) and can boost the frequency up to the internally max allowed clock, based on settings, using a PLL.Given a STM32F103 the internal max clock is 72MHz, but the external signals won't go that high. Half that at best, and the output speed is based on settings.So to answer the OP's question needs more information from his end, as I wrote earlier, but he has not responded to it. Others have raised that same question

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 05:37:19 am
content: Sometimes even with high bandwidth and high sample rate you can't spot the the difference between working and not working.A couple of years back I was developing an optical separation for one wire signals. Wanted opto-couplers on both sides of the line. Managed to design a working circuit, but for a still unknown reason some of the temperature sensors I was using needed an extra 1nF capacitor on the data line to make them work. Used a 500MHz 5Gs/s scope on the signal, but I could not see a difference between the signals to explain it.

author: tggzzz
author_rank: Super Contributor
timestamp: October 04, 2021, 08:36:53 am
content: Quote from: rob77 on October 04, 2021, 01:37:05 amWith on e exception, you are reiterating my points, so I agree.However, when designing a circuit, the first thing you verify is the power supply, since without that all bets are off.Thesecondthing you verify isalwayssignal integrity, since without that all bets are off.

author: nctnico
author_rank: Super Contributor
timestamp: October 04, 2021, 09:20:54 am
content: Quote from: 2N3055 on October 03, 2021, 09:07:23 pmIn general microcontrollers and other chips for which the required risetime doesn't need to be inifinite but can be pre-determined due to the purpose of the chip: the drivers are usually designed to reduce the amount of high frequency content by softening the edges. This not only helps with signal integrity but also to pass EMC testing.

author: tggzzz
author_rank: Super Contributor
timestamp: October 04, 2021, 11:01:47 am
content: Quote from: nctnico on October 04, 2021, 09:20:54 amYes, and with some devices the speed (and voltages) of output(s) is programmable.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 12:46:59 pm
content: I like to measure cycles in my DSPIC, i got the advice to buy a oscilloscope for that reason.Can you see the time also per pulse ?, i need it also with max function, is this all possible ?So if i change 1 piece of code and the function gets 1 cycle slower, i like to see that in exact numbers.I could also hook up a LCD and set up a timer, and write the value,the compiler changes things also, so i better test the real project.Basicly i am optimizing my code and like to measure results instead of gambling.btw : scopes higher then 200MHz are very expensive, not buying anything if it is not cycle accurate enough.Still waiting for newer scopes.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 01:04:08 pm
content: Hi Jan,this is simple to do by setting and clearing an io pin in the code you want to measure. Rise and fall time are not that important for your task. I have used this technique myself to check interrupt routines and guess you can do with a 40MHz scope for that. Single shot is handy if the code is not run that regular.Check your specifications of the DSPic on what the fastest single instruction time is, because that is what you want to see the difference on. The sample rate of the scope has to be sufficient to discriminate between that time interval.

author: joeqsmith
author_rank: Super Contributor
timestamp: October 04, 2021, 01:18:52 pm
content: Quote from: joeqsmith on October 04, 2021, 01:26:59 amhttps://www.edn.com/relating-wideband-dso-rise-time-to-bandwidth-lose-the-0-35/Quote from: Jan Audio on October 04, 2021, 12:46:59 pmLet's assume your setup can change the state of an output ever cycle. So, 1/40MHz or 25ns. Now say you have a 1 second timer and you change it by one cycle. You want to see this 25ns change out of a 1 second pulse? And, let me guess that it needs to do this with a single-shot, so the output does not repeat. And you want to do this with a $100 scope. Maybe you can help with some of my guesses and provide a little more detail on your timing requirements.

author: nctnico
author_rank: Super Contributor
timestamp: October 04, 2021, 01:26:09 pm
content: Quote from: Jan Audio on October 04, 2021, 12:46:59 pmFor this a logic analyser might be more appropriate. For example the Tektronix TLA700 / TLA7000 series. Be prepared for a steep learning curve though. One of the advantages is that logic analysers (at least the professional ones) typically support timestamped recording so it only takes a sample when something changes; this means you can make long measurements (in time) with high timing resolution without needing a whole lot of memory.Another option is to simply use infinite persistence on a DSO and let your program run for a while. Then you can see the minimum and maximum execution times. If you want to use math to get the minimum/maximum cycle you'll need a DSO which uses the acquired data for math instead of a downsampled version of the acquisition record (so R&S and Keysight are not good options).

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 02:20:28 pm
content: Quote from: nctnico on October 04, 2021, 01:26:09 pmNow its getting intresting.I have a analog scope, it only has 2 knobs, more knowledge i dont have.Please tell me what is a good one that have this thing ?, is R&S not top of the line ?I have a feeling i dont have money for this.Quote from: joeqsmith on October 04, 2021, 01:18:52 pmLike pcprogrammer says : Measure interrupt time.Then i want to measure all functions/modules i have, to try a few optimizing tricks.I set the pin high first thing in the function, then low as last thing.Very simple.I need to find peaks in the code,i also use time dividing, having more functions, so i need a 4 channel scope for sure.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 02:29:04 pm
content: Quote from: pcprogrammer on October 04, 2021, 01:04:08 pmIt doesnt matter i need to see 40MHz, if something is 2 times and something 3 times i still need 40MHz.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 02:36:32 pm
content: Quote from: Jan Audio on October 04, 2021, 02:20:28 pmMeasuring more then one pin for timing of software routines will be very tricky because of triggering. A logic analyzer, like nctnico mentioned, will be more useful for that.Which DSP are you using, to give us more of a glue on what timings can be.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 02:41:21 pm
content: DSPIC33FJ128GP802

author: joeqsmith
author_rank: Super Contributor
timestamp: October 04, 2021, 02:49:52 pm
content: Quote from: Jan Audio on October 04, 2021, 02:20:28 pmSay you have some code that pulses at 1.000 kHz. Say you can change that by one cycle, or 25ns and you increase the delay by one. So 1ms + 25ns. This means you need to detect a change of 1000Hz - 999.9750006Hz or a change of 0.024999375 Hz. As you extend that time out, it may make the task more difficult. Say 1 second changing by the same 25ns. It may not be as simple as you suggest when you start considering the details.Maybe a counter would be a better fit.

author: Kean
author_rank: Unknown
timestamp: October 04, 2021, 03:04:27 pm
content: Quote from: joeqsmith on October 04, 2021, 02:49:52 pmI think that is confusing. If you are checking the execution time of an interrupt running at 1kHz, you'd be measuring the length of time spent in the interrupt routine which is presumably a lot less than 1ms. As you know, the repetition rate doesn't really matter as long as it isn't so fast that the interrupt doesn't complete. Just turn on a GPIO at the start of the interrupt, and turn it off before exit.Anyway, a logic analyser like the DSLogic Plus is maybe a good solution for the OP.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 03:17:16 pm
content: Can you recommend a suited model please ?I did not know frequency-counters have math, intresting, hope its cheaper then a scope.

author: nctnico
author_rank: Super Contributor
timestamp: October 04, 2021, 03:19:00 pm
content: Quote from: Jan Audio on October 04, 2021, 02:20:28 pmFor these jobs I definitely use a logic analyser. I have a Tektronix TLA715 myself (for example). What I do is that I give each function a number which is output on a bunch of GPIO pins. The logic analyser can capture these numbers and using the analysis functions it can show me the maximum time and minimum time that is spend in each function. Another option is to create a histogram which shows how much time is spend in each function.I also like joeqsmith's option for a frequency counter. You can use statistics to show min/max and average execution times.

author: nfmax
author_rank: Super Contributor
timestamp: October 04, 2021, 03:21:18 pm
content: If you take a GPIO pin high at the start of the ISR, and low at the end, you can use a pulse width measurement to time it. Most digital oscilloscopes will do this, almost all 'universal' counter-timers will, and many logic analysers can - though with some you may need to fiddle about manually with cursors, etc.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 03:26:24 pm
content: I need what is cheapest and accurate enough.I was just searching and this is the first frequency-counter that is new available i find : Aim-TTi TF960 Frequency Counter 6GHzExpensive, while this is a cheap brand, maybe 6GHz is to fast.

author: tggzzz
author_rank: Super Contributor
timestamp: October 04, 2021, 03:30:24 pm
content: Quote from: Jan Audio on October 04, 2021, 12:46:59 pmIt isn't a simple as that! Caches (instruction, data, branch prediction, TLB, etc) and interrupts will cause variability.If cycle-accurate timing is important, the best option is XMOS xCORE processors running xC. There the IDE will tell you the number of cycles betweenhereandtherewithoutrunning the code.If that isn't an option, then I would use a logic analyser or counter/timer.

author: joeqsmith
author_rank: Super Contributor
timestamp: October 04, 2021, 03:44:50 pm
content: Quote from: Kean on October 04, 2021, 03:04:27 pmIt may not be the time spent in the routine they are trying to measure but rather the rep rate. For example, they are sampling something at a fixed interval. We know they are trying to trim the timing on a cycle by cycle basis. For all I know they use some tight assembler code with NOPs to trigger an SWI. I really don't know what their requirements are so I am just tossing out my thoughts to see if it sparks a response from the OP to help explain some of the details.Quote from: Jan Audio on October 04, 2021, 03:26:24 pmIf you wanted to measure a 25ns change, you won't need much. It's been a long time since I have looked at modern counters, or logic analyzers for that matter. If I understood what you needed, I could attempt to demonstrate it on my old equipment from the dark ages. It may at least help guide your decision by raising other questions.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 03:55:32 pm
content: Quote from: joeqsmith on October 04, 2021, 03:44:50 pmIndeed i want to measure a NOP instruction, nothing more.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 04:06:37 pm
content: Running at a max of 40MIPS with single cycle instructions the setting and the clearing of the io pin would result in 25ns high / 25ns low so 20MHz. Add in several instructions to measure the timing of, et voila the frequency goes down even more.Might even be doable with a cheap 8 channel 24MHz logic analyzer of aliexpress.https://nl.aliexpress.com/item/4000313591159.html

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 04:12:04 pm
content: A Victor VC3165 cost 80 dollar shipped, tax included.Any good for me you think ?*still need to look for logic anylisers, as long as it dont require a computer or smartphone.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 04:19:39 pm
content: Quote from: Jan Audio on October 04, 2021, 04:12:04 pmWhat do you use to compile the code for your DSP?

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 04, 2021, 04:21:07 pm
content: A computer, it is not a reason to buy something that dont works stand-alone.

author: nctnico
author_rank: Super Contributor
timestamp: October 04, 2021, 04:26:22 pm
content: Quote from: Jan Audio on October 04, 2021, 04:12:04 pmThat frequency counter doesn't do you much good. For this purpose you likely end up with a device from HP/Agilent/Keysight or Tektronix.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 04:29:44 pm
content: For the simple test and measurement you are looking at, it is a simple solution to get the logic analyzer I linked to. The Saleae software works with it. Some people frown on using their software without buying their hardware, but if it is for hobby who cares.https://www.saleae.com/downloads/

author: joeqsmith
author_rank: Super Contributor
timestamp: October 04, 2021, 04:30:55 pm
content: Quote from: Jan Audio on October 04, 2021, 03:55:32 pmIt's starting to make some sense to me now.Quote from: Jan Audio on October 04, 2021, 04:12:04 pmCounters are not all the same. You may want to say measure the time from an edge of one channel to the edge on another. I have a very old 70s HP that I like because of some of the modes it supports. Funny, years ago I was at Dayton and I think some of these were pitched. You need to think about how you plan to use it, then look for a counter that has those features.Quote from: Jan Audio on October 04, 2021, 02:41:21 pmI was playing around with a demo board that used a PIC33 DIP part. It may be possible to run your experiment with what I have on hand. Most of my equipment is very old but it may give you some idea what is required.

author: pcprogrammer
author_rank: Super Contributor
timestamp: October 04, 2021, 04:47:01 pm
content: Also an option is to run your DSP at lower speed for the measurements, if it is only for determining the time spend in bits of code and not the real time behavior.For example go down to 10MIPS and do your measurements. The real time operation will be times four when running on 40MIPS. As long as the memory in the DSP is fast enough to run without wait states in either speed.

author: bdunham7
author_rank: Super Contributor
timestamp: October 04, 2021, 05:15:40 pm
content: Quote from: Jan Audio on October 04, 2021, 12:46:59 pmIf I am understanding your problem correctly, the measurement you want is easily* taken with any modern non-crap DSO. If I've misunderstood, please elaborate.Just as an example, I set my Siglent SDS11204X-E up to measure a pulse of about 500us by setting the trigger delay to 500us and the sweep to 100us/div. Then I zoomed in to 10sn/div. I used a signal generator to create a 500us pulse that I can vary in 1ns steps. The pulse has a rise/fall of about 8ns. The two pictures are of a 500us and a 500.01us (+10ns) pulse--you can clearly see how accurately the scope represents this. I could measure one on Tuesday and the other on Thursday and easily tell one from another. The limiting factor in doing this is probably going to be the stability of your DSPIC clock, not the scope--provided you heed my "non-crap" proviso.*"easily" means if you are adept at configuring the scope, not 5 minutes after you take it out of the box

author: tautech
author_rank: Super Contributor
timestamp: October 04, 2021, 06:55:33 pm
content: Wrong advice given post removed.

author: bdunham7
author_rank: Super Contributor
timestamp: October 04, 2021, 07:04:53 pm
content: Quote from: tautech on October 04, 2021, 06:55:33 pmWhat's that?

author: tautech
author_rank: Super Contributor
timestamp: October 04, 2021, 07:20:44 pm
content: Quote from: bdunham7 on October 04, 2021, 07:04:53 pmHave a look in Measurement types.Sorry wrong model, only the 2kX Plus and above offer event counts.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 05, 2021, 10:21:09 am
content: tautech please advice me about some other brand else dont post.

author: thinkfat
author_rank: Unknown
timestamp: October 05, 2021, 10:51:51 am
content: I may be wrong, but I think if you only need to measure e.g. the width of a pulse, then, depending on the accuracy you require, a DSO can be used, if it has a sample rate that is high enough to provide the required resolution. Fidelity of the waveform might not be too important. So even if you have a scope with only 100MHz analog bandwidth, if it samples at e.g. 1Gs/s, you have a temporal resolution of 1ns.Now, the rise/fall time of a "fast" signal will of course be determined by the analog bandwidth of the scope, but still, that will delay both the rising and the falling edge of the pulse and you should still be able to measure the width with enough accuracy, e.g. if you use cursors placed on 10% rising and 90% falling edge.Couple that with the fact that your pulse width will itself have the granularity of the cycle time of the processor and you only need to measure the number of cycles, I'd say even a cheap 1Gs/s 100MHz scope is enough for the purpose.

author: rodpp
author_rank: Frequent Contributor
timestamp: October 05, 2021, 10:54:33 am
content: Quote from: Jan Audio on October 05, 2021, 10:21:09 amAs tautech is a Siglent vendor, it's his interest to give advices only for Siglent equipment, it's understandable.If the EEVBlog allows this kind of "marketing", there is nothing wrong with tautech doing that, in my opinion of course.Even if you don't want to buy a Siglent, it's an open forum and the answers can be read for orhers with similar necessities, so by potential new Siglent clients.I would prefer that EEVBlog opinions/advices were clear of this kind of marketing, but it is not.

author: tggzzz
author_rank: Super Contributor
timestamp: October 05, 2021, 11:14:07 am
content: Quote from: thinkfat on October 05, 2021, 10:51:51 amThat is a good starting point, but itmightbe complicated byhaving a slightly different "strengths" for the device's pullup and pull down output transistorsinternal (digital) signal processinginternal differing slew rates for rising and falling voltagesI would hope any such effects would be small, but I would want to do simple measurements to determine how close to the, say, 1ns resolution is achievable in practice. I expect you would do the same!

author: thinkfat
author_rank: Unknown
timestamp: October 05, 2021, 11:21:03 am
content: I agree, I'm building on the assumption that the pulse width will be multiples of 25ns, as the DSP can do 40MIPS only. If you can make out the difference between a 25ns pulse and a 50ns pulse it's enough.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 05, 2021, 01:30:06 pm
content: Yes and the thing is i want for 48MHz also, PIC32MX

author: bdunham7
author_rank: Super Contributor
timestamp: October 05, 2021, 01:48:12 pm
content: Quote from: rodpp on October 05, 2021, 10:54:33 amReally? You think EEVBlog is worse off because official or unofficial company reps show up and provide information and support? I wish there were more of them, so don't scare them off.

author: Old Printer
author_rank: Frequent Contributor
timestamp: October 05, 2021, 02:02:12 pm
content: Quote from: bdunham7 on October 05, 2021, 01:48:12 pmAgreed! Tautech is a Siglent distributor in New Zeland, yet responds to all sorts of requests for Siglent info and support from all over the globe. I can't count the number of people he has helped, me included, but when he offers Siglent products people jump on him as if he got a commission on every Siglent sale.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 05, 2021, 02:18:20 pm
content: Whatever, just dont advice me about any siglent please.Buying any other brand, searching for a cheap solution.I go search for frequency-counters and that logic anylizer if i can find any cheap without PC required.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 05, 2021, 02:49:26 pm
content: I am looking in the manual for the aim-tti :https://resources.aimtti.com/datasheets/AIM-TF900+PFM3000_series_frequency_counters_data_sheet-Iss3A.pdfIt says :Eight significant digits of answer are produced in a 1 second measurementtime, nine digits in 10s and ten digits in 100s with a granularity of less than 2counts in the least significant digit.So it needs to measure at least 1 second, i think it is not suited.

author: rodpp
author_rank: Frequent Contributor
timestamp: October 05, 2021, 03:39:24 pm
content: Quote from: bdunham7 on October 05, 2021, 01:48:12 pmNo! Not because they provide information and support. But because the side effect of pushing their equipment ineverytopic asking "What xxx should I buy...".And worse is not a good word to say, because EEVBlog is a great place and community, and I like to frequent here. It's only my preference that, if I could choose, I would like to not have this kind of marketing in every topic searching for advices about what equipment to buy.

author: tggzzz
author_rank: Super Contributor
timestamp: October 05, 2021, 03:59:49 pm
content: Quote from: thinkfat on October 05, 2021, 11:21:03 amWho knows!The xCORE devices can have i/o clocked at 250MHz/4ns and there is language support for specifying on exactly which clock cycle the output occurs (or input is read). However each (of the many) cores only operates at 100MHz/10ns.I'm sure many other devices have similar capabilities, if not language support. e.g. aPort <: outputData @ clockCcount; forces outputData to appear on aPort's pins when the port's clock counter is clockCount.

author: Fungus
author_rank: Super Contributor
timestamp: October 05, 2021, 04:08:54 pm
content: Quote from: rodpp on October 05, 2021, 10:54:33 amSure, but he butts into every single thread that even mentions oscilloscopes. No matter the stated budgets or stated requirements.Quote from: Old Printer on October 05, 2021, 02:02:12 pmI don't believe anybody here has a problem with him offering support in the Siglent threads, when anybody specifically asks for information about a Siglent, or even doing a sales pitch in a "which is better, Siglent or brand X?" thread.

author: nfmax
author_rank: Super Contributor
timestamp: October 05, 2021, 04:25:22 pm
content: Quote from: Jan Audio on October 05, 2021, 02:49:26 pmThis is a frequency counter, what you want is what used to be called a 'universal timer-counter', that can measure either a pulse width on a single channel, or a time interval from one channel to another. You need a 'frequency range' of 100MHz to get a 10ns time resolution on a single-shot measurement.This would do it, if it works (I have one myself):https://www.ebay.co.uk/itm/363543300386Or maybe this one, if you connect the inputs together (I haven't personally used one):https://www.ebay.co.uk/itm/255150981466There are plenty of other instruments on eBay at the moment, but they seem a bit expensive. HP, Racal-Dana, Fluke are likely manufacturers. You don't need a high stability or accuracy oscillator for your purposes, which may make it easier to find one.

author: bdunham7
author_rank: Super Contributor
timestamp: October 05, 2021, 04:40:53 pm
content: Quote from: Jan Audio on October 05, 2021, 02:18:20 pmI simply showed you how to accomplish what I think you are trying to do. I happen to have a Siglent scope, but as I clearly stated, any 'non-crap modern DSO' will do the same. Perhaps someone with the inexpensive 2-channel Rigol DS1102Z-E ($249 US) can demonstrate the same things that I did if you really just can't stand to look at the Siglent name. I'm pretty sure it would work, but I don't have one and haven't tried it.

author: nctnico
author_rank: Super Contributor
timestamp: October 05, 2021, 04:46:41 pm
content: Quote from: Jan Audio on October 05, 2021, 02:49:26 pmNo. What you need is a time interval / pulse width measurement. For that it needs to measure for the duration (width) of the pulse or time interval (edge to edge).

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 06, 2021, 01:24:44 pm
content: Quote from: nfmax on October 05, 2021, 04:25:22 pmThank you very much nfmax.Are those things not new available in a modern version ?I like to buy things new.If i type 'universal timer-counter' in google the first advertisement i get is the TF960.Then i see for the rest of the page these for 2 to 3 thousand euros :https://www.keysight.com/nl/en/products/frequency-counter-products.htmlDo i need to look further ?Quote from: nctnico on October 05, 2021, 04:46:41 pmWich one ?I think i ask for something that dont exists again.

author: nctnico
author_rank: Super Contributor
timestamp: October 06, 2021, 02:25:04 pm
content: Quote from: Jan Audio on October 06, 2021, 01:24:44 pmNo. Time/interval is a feature found on most professional frequency counters like the ones from HP/Agilent/Keysight or Tektronix. However I strongly suggest to do some reading into the subject. IOW: try to find some tutorials / videos on the basics of using a frequency / time interval counter. From there you get a better grip on what you need to look for.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 06, 2021, 03:31:57 pm
content: B&K have time interval measure in a discontinued product, not in the newer model :discontinued :https://www.bkprecision.com/products/counters/frequency-counters/1823A-2-4-ghz-universal-frequency-counter-with-ratio-function.htmlcurrent model :https://www.bkprecision.com/products/counters/frequency-counters/1856D-3-5-ghz-multifunction-counter-frequency-period-totalize.htmlMouser has the 1823A for € 500,-Stock:11 Can Dispatch ImmediatelyEnd of Life: Scheduled for obsolescence and will be discontinued by the manufacturer.Hmz, have to make a choise soon, why dont the newer version have this function ?

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 06, 2021, 03:36:52 pm
content: By the way what other brands have relabels of the B&K 1823A ?

author: nctnico
author_rank: Super Contributor
timestamp: October 06, 2021, 03:55:01 pm
content: Look for an HP/Agilent 53131 or 53132 frequency counter. This can also do statistics and they aren't very expensive when bought used from Ebay.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 06, 2021, 04:06:31 pm
content: That looks the same as the B&K, ebay prices are around 500 also.That is without tax and handling cost, better order the B&K then, only 500 is to much for this.And i have doubts if it works accurate enough, 10ns timebase ?, 500 euro.

author: nctnico
author_rank: Super Contributor
timestamp: October 06, 2021, 04:40:29 pm
content: The B&K doesn't seem to have statistic so it can't show you min, max & average values over a bunch of measurements. Ebay asking prices usually aren't the sale prices. You should be able to get one much cheaper and the Ebay global shipping program has pretty good pricing for shipping (which includes VAT and customs handling fees).

author: bdunham7
author_rank: Super Contributor
timestamp: October 06, 2021, 05:07:56 pm
content: Quote from: Jan Audio on October 06, 2021, 04:06:31 pmIf you are going to insist on using a universal counter for this, takenctnico's advice and do some reading on the subject.The BK1823A is not going to work for your application. This would be readily evident if you read the manual. The 1856D is not 'newer', simply a different model.Basic reciprocal universal counter timers are limited in time resolution by their clock frequency. A counter with a 10MHz clock, like the BK1823A, is inherently limited to a 100ns time resolution--unless additional steps are taken. The AimTTi TF930/TF960 use a 50MHz clock, so it is limited to 20ns.To overcome this inherent limitation, there are two common methods used to increase time resolution--averaging and vernier interpolation. The BK1823A does neither, AFAIK. Counters like the TTi TF930/960 and my HP 5316B use averaging to add a few digits--but this requires a steady, repetitive signal or the results are nonsense. Counters like the old monster HP 5370B I have lurking in my garage or the 53131-series HP's use vernier interpolation and can provide resolutions down to the tens of picoseconds for a single event. Not all modern counters include this feature! If you look at Keysight's current offerings, the 53210A does not have this, while its two more expensive siblings do.Finally, you also need to worry that whatever you get has the appropriate triggering setup--you need to either have an explicit pulse-width function, or as on my HP 5316B, a TI A-B function with the ability to invert and adjust both channels. You need to branch off and feed the signal into both channels with this setup. You also need to consider that the rise/fall times may be significant compared to the time delta you are trying to measure, so repeatability may be an issue. Remember what I said earlier about being able to tell the difference between a 500.00ns and a 500.01ns pulse even if I measure one one day and the other the next? That might be much more difficult with a counter.Frankly I think you are taking the most difficult route to do this with no apparent gain over a simple DSO. The only additional thing you might do with a counter, provided you can set it all up, is to count the actual DSPIC clock cycles over the pulse width. However, if you don't have access to the DSPIC clock--say your external clock is 8Mhz and the internal clock is PLL-multiplied 5X--then that doesn't work either. So what was wrong with the method I showed you? Does it not accomplish your purpose?

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 07, 2021, 01:09:46 pm
content: Indeed i want a scope, it is more usefull.Waiting for something new to release from a cerain brand.Maybe GW start making scopes that look nice, just like the R&S.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: October 08, 2021, 01:56:17 pm
content: Is the Rigol DS1202Z-E any good for this purpose ?Ok not 4 channel, 200MHz yes, 360 euros.

author: bdunham7
author_rank: Super Contributor
timestamp: October 09, 2021, 12:13:11 am
content: Quote from: Jan Audio on October 08, 2021, 01:56:17 pmI would be extremely surprised if it was unable to do the same thing I demonstrated. That said, I have not actually tried it because I don't have one.

author: Bassman59
author_rank: Super Contributor
timestamp: October 09, 2021, 01:34:07 am
content: Quote from: Jan Audio on October 07, 2021, 01:09:46 pmOK, I read through this entire thread and ...At the day job I do FPGA designs and for various reasons we tend to use a 100 MHz oscillator for the "main" clock in many designs. (Other clocks are generated with PLLs or whatever.) I have a Tek TDS3054 on the bench: 500 MHz analog bandwidth, 2 Gs/s sampling, four channels. I drive otherwise-unused FPGA pins as test points, so it's common for a pin to drive a 10 ns-wide pulse. I can clearly see and trigger on those pulses with that 'scope. That 'scope was also pretty expensive.My personal projects are digital audio things, so you can figure there is a 24.576 MHz clock running around. One thing I did used a PLL inside an FPGA to bump that up 4x to 98.304 MHz. I brought that clock out to a test pin to verify it. My 'scope at home is the humble and old and pretty much obsolete Tek TDS2024 (first version), so 4 channels, 200 MHz analog bandwidth, 2 Gs/s sampling. I bought it new ages ago -- seriously, it's 15 years old. It has limited memory, a useless FFT, a tiny display, no serial protocol decoding, no USB, no ethernet, no anything special. It was the only affordable DSO available when I bought it. It is worth maybe $100 now. Here's the funny thing, though:It is perfectly fine for my needs with this application.Looking at 20 MHz SPI ports? Fine. Looking at I2C? Piece of cake. Looking at I2S? Works well enough. Looking at audio and triggering on a digital event on another channel? Sure!Do Iwanta new oscilloscope? Sure! Who doesn't. The problem is that I want a 350 MHz-or-better analog bandwidth on four channels and I don't have the budget for something I "want." If Ineededthat bandwidth, I would have bought something already. And there's no point in buying the same bandwidth and sampling, even if I'll pay less money and get more memory and a nicer display.And that's my point. I think that any of the four-channel 200 MHz analog/2 Gs/s sampling oscilloscopes will be fine for your application. I don't know how this discussion veered off into frequency-counting but any decent 'scope will show a reasonably-accurate measurement of the frequency of a repetitive signal. If you need something more specific, that's a different instrument.Good luck.

author: 2N3055
author_rank: Super Contributor
timestamp: October 09, 2021, 08:45:10 am
content: Quote from: Jan Audio on October 08, 2021, 01:56:17 pmI still don't understand what exactly you want to do here:1. Do you toggle pin ON on some part of code and then toggle it OFF ont he end of the code fragment to measure how long it took to execute ?2. Do you quickly toggle pin ON/OFF to create quick pulse and then measure how many times per second something gets called (executed)Both are valid profiling questions.If you want number 1. :bdunham7 have shown you how it can be done. He used SDS1104X-E because that is what he has and it works well. That scope uses full memory data for measurements and have good timing resolution. Enable statistics and have Mean, Min, Max, Standard Deviation for more information on data.That will show you maximum, minimum, average and RMS variation of execution times.On SDS1104X-E you will be able to easily measure that time with ns level resolution, so better than you need.Use pulse width trigger to capture only times when pulse was shorter, longer, within or outside specified range.Any other scope that has same functions and measures on whole memory will be able to do the same.Rigol 1000Z series are measuring from decimated buffer. Also Keysight Infiniivision does. GW Instek too, and R&S does too. That takes away some precision on longer timebases. They all decimate differently so they don't loose precision same way. Keysight also looses precision quickly on longer timebases because of small memory forcing slow sampling rates. It also might or not be important, because maybe you don't need soo much decimals.Siglent uses full resolution data, new Rigol 5000/7000/8000 series can also (they have choice of fast/full precision mode), and I never checked Micsig STO1000 series, but that on doesn't have statistics..On Siglent SDS2000X+ series you can also plot a graph ( a track plot) of how execution time changes...But for this use a scope of the class of SDS1104X-E would do a good job.for 2.That is a counting job. You can also use scope for that.Also by toggling several pins from different parts of code you can even watch call sequence and response times and such. Only limit is your imagination.That is why scope is a good tool, it is very universal..

author: nctnico
author_rank: Super Contributor
timestamp: October 09, 2021, 09:02:45 pm
content: Quote from: Bassman59 on October 09, 2021, 01:34:07 amWell, that is because Jan's interest is also measuring execution times of software by toggling GPIO pins with great precision over an extended period of time. An oscilloscope isn't the right tool for that job. But now he is back at buying an oscilloscope because it seems like a more versatile tool to him so it could be a better purchase for him all things considered (we can't spend his money).However, for profiling my choice would definitely be a professional (from Tektronix or Agilent) logic analyser.Quote from: 2N3055 on October 09, 2021, 08:45:10 amNo. GW Instek uses the acquisition memory. You can choose entire memory, screen or between the cursors.

author: bdunham7
author_rank: Super Contributor
timestamp: October 09, 2021, 09:35:18 pm
content: Quote from: 2N3055 on October 09, 2021, 08:45:10 amIf I understand what he' s trying to do, it can be done even with a much lesser scope. I have a TPS 2024 which is similar in function toBassman59's old TDS 2024 (except for the very handy isolated channels, of course) and you can do fair job on that even though it only has 2.5k points. All you really need is for the trigger delay to be accurate, or if you are just comparing the two pulses with and without the extra NOP, then the trigger delay just has to be stable. I could probably manage using the delayed B-sweep on any decent old analog scope.As far as universal counters go, all I'll say is that it is a lot easier to make sure you're measuring what you intend to measure when you can see it on a scope.

author: 2N3055
author_rank: Super Contributor
timestamp: October 09, 2021, 09:57:34 pm
content: Quote from: nctnico on October 09, 2021, 09:02:45 pmMeaning that it will keep 1 ns resolution on single shot timing measurements at 1ms/div with 10 MPts of memory enabled.?It can measure 8ms pulse with single shot 1 ns resolution?If that is so, I stand corrected..Thanks!

author: 2N3055
author_rank: Super Contributor
timestamp: October 09, 2021, 10:04:07 pm
content: Quote from: bdunham7 on October 09, 2021, 09:35:18 pmWith counters, it will also depend on how you set trigger level. All digital signals have a bit limited rise/fall time. Depending on where you put trigger level you get different pulse width... Some counters will have intelligent auto level set, and some will be fully manual. If you keep trigger level consistent between measurements you can get good relative measurements. On scope you are not flying blind.Some scopes have decent counter and totalizer, but I guess those are out of reach and overkill for OP.

author: nctnico
author_rank: Super Contributor
timestamp: October 09, 2021, 11:24:36 pm
content: Quote from: 2N3055 on October 09, 2021, 09:57:34 pmYou don't need to have a high samplerate to determine the position of an edge if you can sample multiple levels (IOW: are able to reconstruct the actual signal). It will depend on the algorithm used but as long as the pulse can be detected, you can determine the edge. The pulse counting algorithm can easely interpolate the level + time and go from there. Maybe I have some time to try but I think most DSOs won't show the result with enough digits to make such a precise measurement.

author: 2N3055
author_rank: Super Contributor
timestamp: October 09, 2021, 11:50:25 pm
content: Quote from: nctnico on October 09, 2021, 11:24:36 pmSome will, some won't. If you have time you should try it on GW Instek 2000E, I'm curious if it will.I know for sure that SDS1104X-E will, and higher touch screen Siglent models will do better than 1 ns (because of higher sampling rate).I cannot check but presume new touch screen Rigols (0500/7000/8000) should do it as well in high accuracy mode (they have two modes to chose, fast and high accuracy).My MSOX3104T cannot do it at those settings.Point is, the full memory gives you, lets call it large timing "dynamic range", timing resolution. You can measure 1ms pulse and accurately see nanosecond level changes... Pretty much you can literally count cycles on a long running function call.How important and useful that is is another question. I personally think it might be useful for things like measuring interrupt caused jitter on something that is really time critical... Sounds like something of a special case..For something so critical, I guess you should use software/hardware architecture that will guarantee specs..

author: bdunham7
author_rank: Super Contributor
timestamp: October 10, 2021, 01:29:10 am
content: You can position an edge better than the sample rate and way better than the bandwidth, but having more of either is certainly helpful--and lets you stretch the process even further. The Siglent has a 10ns resolution on the displayed pulse width measurement--why not 1ns I'm not sure--but using the absolute values of the cursors you can get as precise as you think you can eyeball the transition point. The actual cursor readout is in increments as small as 20ps, but that's way too small to see at 1ns/div. I would be pretty confident in a discernible resolution of 100-200ps here.

author: 2N3055
author_rank: Super Contributor
timestamp: October 10, 2021, 08:38:23 am
content: Quote from: bdunham7 on October 10, 2021, 01:29:10 amMemory depth you set is 1.4MPts. Could you try with 14 Mpts?

author: StillTrying
author_rank: Super Contributor
timestamp: October 10, 2021, 10:53:45 am
content: To measure small 5 to 20ns times or delays, I sometimes move the waveform(s) around with Channel Skew. you canfeel around 1/10 of an X pixel width if you have to.As long as there's 2 samples on the fast edge sinx seems the draw the edge's half amplitude in an accurate X position.

author: bdunham7
author_rank: Super Contributor
timestamp: October 10, 2021, 02:23:08 pm
content: Quote from: 2N3055 on October 10, 2021, 08:38:23 amMemory depth is at maximum for that sweep rate--100us/div X 1GSa/s = 100k points, x 14 div = 1.4Mpts.

author: 2N3055
author_rank: Super Contributor
timestamp: October 10, 2021, 06:18:53 pm
content: Quote from: bdunham7 on October 10, 2021, 02:23:08 pmYes I know. I meant 1 ms/div and 14 MPts.

author: bdunham7
author_rank: Super Contributor
timestamp: October 10, 2021, 07:59:28 pm
content: Not much difference, you only get one set of dots unless you turn on persistence, so the faux-ETS doesn't look as good. In vector mode, it's just a tiny bit wiggly.Edit: It occurs to me that this is a million X zoom! That seems impressive somehow, especially since it is all still very accurate and steady.