Astronics PXIe-2461 period measurement problem

[quantum_x]

Hello everyone,

I use the Astronics PXIe-2461 Universal counter timer to measure phase shift of phase modulated signal (PM) that means one of two pulse change period in time periodaclly with out changing the pulse width and that make it hard for the PXIe-2461 it give two periods simultaneously, I thought that was related to trigger hysterisis's level and gate time settings i tried a lots of settings configurations but it didn't work.
Just for informations the PXIe-2461 give precise measure with a non frequency or phase modulated sinusoïdal or periodic signal.
Your ideas and suggestion are welcome, thank you

Here is the Pxie-2461 datasheet:

https://www.astronics.com/docs/default-source/Documents-ats/current-datasheets/universal-counter-tim...

I put also the user manual in Attactched file.

[cg_Astronics_Test_Systems]

Hello Quantum_x,

I apologize for waiting months to answer this query as I only just discovered it by searching the NI website. I will see if there is a way to improve this process in the future. In the meantime, posting queries to the Astronics Test Systems website (www.astronicstestsystems.com) as well should speed things up.

It sounds like you want to measure the phase shift between two signals, but you mention that one of the two signals changes its period "periodically". To me that suggests that the period on both channels is different. Automatic phase measurement mode of the PXIe-2461 could potentially fail to measure phase in this case because it requires the period measured by both channels to be essentially the same before it attempts to complete the phase measurement. Let me know if that is the case.

If the period is consistently the same on both channels, the automatic phase measurement mode should continue on to measure the time interval (TI) between the zero phase point of the phase reference signal and the zero phase point on the phase shifted channel. The phase is then calculated as 360° x (TI/PERIOD).

So, as long as the period is consistent on both channels, you should be successful at making a phase measurement. If the period is changing on either channel, the phase algorithm will fail because phase measurement is meaningless, at least in the sense of what the counter measures, when the two channels are not of the same frequency.

In any case, I thought that explaining the criteria for an automatic phase measurement would help you with this application. I can also suggest that if the period is not consistent enough, you should have better luck determining the "raw phase" by measuring the time between the zero phase event on the reference channel and the zero phase event on the shifted channel using TI mode. If you know or measure the period on the reference channel, you can translate the TI measurement into a raw phase measurement using the equation phase = 360° x (TI/PERIOD). That way you don't have to worry about the period of the shifted channel and can measure the raw phase shift that way.