Phase shift is (delay/period) * 360 degrees. So, I get 0.9216 degrees for a delay of 20ns with a period of 7.8125us. Note also that if the signal being measured lags behind the reference, the phase shift is considered negative. If it leads, the shift is considered positive. This works out for calculating shifts using phasers or complex numbers. For example, if we have an inductor with a reactance of 2 ohms, its impedance is 0+j2 . If we apply 1V at an angle of zero degrees (our reference) or 1+jo, we can apply Ohm's law as below:

I=V/Z = (1+j0)/(0+j2) = (1<0)/(2<90) = 0.5<-90

I used < here as the "angle sign", so 1<0 is read as "1 at 0 degrees). So, the result here is 500mA at an angle of -90 degrees. So, the current lags the voltage by 90 degrees (as we expect for an inductor).

For more on this, see http://www.hallikainen.org/rw/theory/

Harold



--- Duane Brantley <dbrantley@AUSTIN.RR.COM> wrote:


If the period of a 128KHz sine wave is 7.8125uS and I measure a phase
shift of 20nS, how do I determine what the phase shift is in degrees?

Thanks,
Duane
--


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