On 07-Jun-11 22:05, RNGolding@aol.com wrote:
> Hi, not sure if this should be PIC or EE, but I have opted for  PIC
>
> I have an application where I need to measure the phase difference betwee=
n
> two sine waves of same frequency. I'm using two zero crossing detectors t=
o
> trigger the CCP1 and CCP2 inputs of a PIC. The CCP counter is  clocked by=
 a
> PLL/VCO at 360 x the sine wave frequency, so the  difference between the
> CCP1 and CCP2 counts provides a direct phase measurement  with a resoluti=
on of
> 1 degree.
>
> So far so good, however the sine waves have some jitter so I thought I
> would take the average of a few consecutive phase measurements. That is  =
where
> I come unstuck, how do you average phase readings?
>
> To illustrate the problem, if the phase is jittering about zero  degrees
> giving 4 phase readings of say, 358, 359, 1 and  2 degrees, a simple aver=
age
> calculation yields 180 deg, which is  obviously wrong. Does anyone know h=
ow
> calculate the true average,  which  should be 0 degrees? I'm sure the ans=
wer
> is obvious, but it has defeated me so  far.
>
>   Richard Golding
>

http://www.webmet.com/met_monitoring/621.html

Djula
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