Can somebody provide me a guidance about how the phase between an analog and tacho channel is calculated? I don't believe people are actually using any method in time domain to detect the phase. Do people use cross-spectrum method? If cross-spectrum is used, how the tacho signal, which is essentially a series pulses, be represented and used?

Thanks,

James

I think that when you have a tach or reference input, the pulse triggers the data acquisition. The phase data would be extracted from the complex FFT output.

Tachometer senses the passing of a reflective tape
and triggers the counting of start time. The end time is when the heavy spot reaches the vibration sensor. The difference of the time divided by angular velocity is phase angle. Thus the phase angle is the time(Actually it is measured in terms of time and converted to angle) taken by the heavy spot to reach the vibration sensor starting from the time the reflective4 tape passes the tachometer.
Regards.