measure phase shift

[mario_pyr]

Hi!

I have got a question relating the measurement of the phase-shift between an in- and outgoing voltage (both analog and the same frequency) of my DAQ-Device.

I can´t find a VI to detect or measure the phase-shift and I don´t know how to solve this problem. So somebody can help me? Somenone can tell me if there´s a VI in the /examples folder or can send me a self-made VI? Or someone just can tell me how to begin...???

Thanks!

mario_pyr@hotmail.com

[mario_pyr]

Sorry, there was a mistake in my description...

I want to measure the phase shift between two incoming signals!

No one has got an idea?

[ciramjo]

Mario,

This is a difficult thing to do accurately in software. Since the two signals may be different amplitudes, you need to measure the time difference between the zero crossings.  Sample the two signals at a high rate using a simultaneous sample and hold A/D card, then measure (calculate) the time difference between each signal's zero reading (i.e. the zero crossing).

Hope this helps,

John

[mario_pyr]

Ok, thanks...

... it sounds good, but how can I calculate the time (sorry, I´m a beginner)? I can´t find a VI to measure time between two processes. So I have to program it myself? What makes the timer start and what makes it stop?

Mario

[ciramjo]

Capture the data using a timed loop. There is a loop parameter called "actual start time" that you can capture along with the data and use to calculate dt. Run the loop as fast as possible. You can use shift registers and the switch function to capture and latch the time at the zero crossings (+/- some tolerance) and do the calculation in real time, assuming your input signals are of a low enough frequency.