Vector volmeter question

[happybird]

Thanks for your reply,actually,i have changed the VI(Niw_main.VI) you post,attached is the modified VI,and i use it to do measurement,but i find that the phase is always shifting, so could you please give me any suggestion?

[DFGray]

I see one problem that may cause jitter. When you converted to the HP driver, you threw away the phase and sample period info the analysis routine needs to do its job correctly. You need to convert the HP outputs to waveform data types. Here is an example.

.

Build the waveform using the components of the HP output. Alternately, you can change the driver output to be a waveform.

This may not solve your problem. There are many possible causes for jitter in your phase. We have alreadly listed some of these in previous posts. Without access to your experimental setup and/or data, about all we can do is speculate. Good luck!