Measure phase shift of response?

[sunnyg]

Hola,

Just wanted to output a square wave signal to a circuit using an m-series DAQ card and Labview 7. Wanted to use same card to detect response from circuit (presumably at same frequency but returned as a sine or cosine at different amplitude) and look at phase shift between the output signal and input signal. Assuming a simple function generator to DAQ assistant for the output signal and a DAQ assistant to single tone measurement for the input. Should this work if I subtract the phases to find any shift? Also, do you think a trigger would be needed here?

Any help would be much appreciated,

Sunny

[Jennifer O]

Hello Sunny,

To perform phase measurement between 2 signals it is important to synchronize your signals in order not to introduce error. Triggering, and sampling using a shared clock will allow you to synchronize analog input and output. 

I recommend beginning with an example program to synchronize your analog input and output tasks.  You can then analyze the two signals (perhaps with the Frequency Response Function.vi) to measure phase shift. Try working with the 'Multi-Function-Synch AI-AO.vi' located in Help>>Find Examples>>Hardware Input and Output>>DAQmx>>Synchronization>>Multi-Function.

I hope this is helpful.

Regards,
Jennifer O.