Rigol DS1054Z phase measurement - Page 1
Forum section: electronics / testgear

author: palindrom71
author_rank: Contributor
timestamp: April 01, 2025, 08:56:17 am
content: I'm preparing for a long measurement of phase difference between 2 sinusoidal signals, both 10MHz.That Rigol is all I have available for now so it have to do. I'm aiming for resolution.I'll set up RaspberryPi with lxi tools.Question 1:How to get the most of the phase measurement in that scope?The approaches I thought of::MEASure:STATistic:ITEM AVERages, RPHase,CHANnel1,CHANnel2Now this doesn't give me control over the average and that's problematic, as I can probably reset statistics after each acquisition but that's all I can do. I don't know how the scope calculates these averages and if I can get better precision if I use consecutive :MEASure:ITEM RPHase and calculate moving average afterwards. That will be a lot of data though. In average mode I'm thinking of taking a measurement each 10 seconds or so.But then, there's XY mode so I could measure phase from Lissajous figures. So...:TIMebase:MODE XYIn that mode I could calculate phase with cursor tracking but that's again an intersection measurement so I don't think it will be any better than just measure the phase off the edges of time domain signal.I couldn't find a phase measurement that would take the whole Lissajous figure. Or did I just miss it?Question 2:Do we know how phase measurement is implemented in DS1054Z? does it take multiple edges on both signals? If yes, only displayed ones? If it takes all the edges, it probably would be reasonable to set 500Ms/s and manually 54M memory. Unless it takes only visible waveform then too bad.Any help appreciated!

author: Someone
author_rank: Super Contributor
timestamp: April 01, 2025, 09:42:44 am
content: Quote from: palindrom71 on April 01, 2025, 08:56:17 amDownload the waveform and compute the phase offline.Is the phase difference always going to be small? or are you trying to cover arbitrary phase?

author: ch_scr
author_rank: Frequent Contributor
timestamp: April 01, 2025, 09:51:57 am
content: Phase Resolution is limited by the sampling rate of the scope.Freq 10 MHz -> Period 100ns -> divide by 360 (degree) -> ~278ps per degreeWith the 1 Gsample of the Rigol the samples will be 1ns spaced apart.Since both are sinewaves, the zero crossing could be more precisely detected from the interpolated line between the samples.Scopes often have the option to measure "once" (e.g. with a cursor showing it) or "all" (e.g. zero crossings) across the sampled memory.Quote from: Someone on April 01, 2025, 09:42:44 amAgree, likely the Rigol won't do what you want (or as good as you want it) on-device

author: Someone
author_rank: Super Contributor
timestamp: April 01, 2025, 09:59:19 am
content: Quote from: ch_scr on April 01, 2025, 09:51:57 amNope. Processing gain can go far beyond a single LSB of one axis.

author: palindrom71
author_rank: Contributor
timestamp: April 01, 2025, 10:00:22 am
content: Quote from: Someone on April 01, 2025, 09:42:44 amVery small. On 10Mhz signal I expect a deviations in the range of 1uHz to 10mHz. That's why I want to take measurement for a couple of days.Quote from: ch_scr on April 01, 2025, 09:51:57 amI was hoping for Rigol to at least average across multiple zero crossing. Well, it looks my CPU won't be happy when I take it offline.

author: 2N3055
author_rank: Super Contributor
timestamp: April 01, 2025, 10:30:15 am
content: DS1054Z measure phase once per trigger on first edge from the left side of the screen. That is all.Measurements are based on decimated screen data. As in pixels.Timing resolution as such based on timebase.You need to run fastest timebase possible.If you can visually see difference in phase between 2 channels it will measure it.Otherwise, not much luck.That is not a good scope for that kind of measurement.If phase difference is something you need to measure a dedicated device will do much better job.Look at TinyPFA phase frequency analyser.https://eleshop.eu/tinypfa-phase-frequency-analyzer.html

author: palindrom71
author_rank: Contributor
timestamp: April 02, 2025, 08:42:54 pm
content: Thank you for the answers!I just finished playing around with Rigol over LXI. It's a no-go for what I need it for, by 3 orders of magnitude, but I'll try TinyPFA approach.For wanderers, I'm leaving here Octave scripts / scratchpad I used to play around. There's everything there to setup and perform aquisition over the Ethernet with no drivers at all.I had to restrict parameters for fitting, as fitting a sine is a major pain. Frequency is fixed.Anyway, it was fun.Cheers!

author: Andreas
author_rank: Super Contributor
timestamp: April 02, 2025, 09:05:28 pm
content: If you have math functions you might get it like in old PicoScope 6 Software:https://www.picotech.com/support/viewtopic.php?t=10569newer PicoScope 7 software has this already integrated.with best regardsAndreas