Why the phase is shifting?

[happybird]

Hellow!

Attached is a simple simulation of a program to get the phase of a sin wave,anyone can tell me why the phase result is always shifting? Is it a right way to measure phase? thanks!

Message Edited by happybird on 07-16-2005 07:25 PM

[altenbach]

Your phase is not shifting!

Change the phase indcator to a more resonable format, (e.g. 5 decimal digit resolution) and it will always be zero. Currently, it is a few hundred pico-degrees (0.0000000001 degrees). This is zero within the precision of the algorithm. 🙂

[happybird]

Thanks for your reply,could you please look at the original program,it also has been simplified.could you please let me know your suggestion about why the phase is changing,but the frequency and amplitude seems to be stable.

[altenbach]

Sorry, I am not familiar with your instrument. What kind of signal are you measuring?

(For example if your loop frequency is not locked in some way to the continuous analog signal, you phase will be random from measurement to measurement.)

[happybird]

The signal is a simple sine wave,what do you mean by " loop frequency" ?is it the frequency of the while loop?,then how to locked the loop frequency  to the continuous analog signal,thanks!