Re: Precision Phase angle measurement


"psdayama" <psdayama@xxxxxxxxx> wrote in message
news:1164627163.985868.212530@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,
I am trying to measure phase angle difference between nearly
identical sinusoidal waveforms.
I am presently trying with comparators as zero crossing detectors. Then
run a counter with 2Mhz
clock with either rising or falling edge. However results are very poor
: accuracy of only 30minutes
and result (stability)varying from 30minutes at 20% nominal voltage to
- 10 minutes at 120% voltage.
Results are better for rising edge and poor for falling edge.
Comparators are LM339. Nominal
voltage is 1.42V rms or 2.048Volts peak.
Can anyone suggest a method to achieve atleast 5minutes of stability
for varying input volages?
Thanks in advance,
purushottam

You don't menntion what the frequencies are so we can't tell what 5 minutes
equates to in terms of time....particularly in relation to your use of 2MHz
sampling. Further errors might be caused by hysteresis in the zero crossing
detector used to eliminate noise.

Do you need to know the phase error cycle by cycle or averaged over 100
years?

How about putting one sin into a variable delay line and summing the output
with the other sine on a sample by sample basis. Then adjust the delay until
the output is a minimum.


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