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'[EE] phase shift'
2003\05\01@152250 by Duane Brantley

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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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2003\05\01@153519 by Spehro Pefhany

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At 02:21 PM 5/1/2003 -0500, you 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?

360° * 0.02us/7.8125us  ~= 0.92°

Best regards,

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2003\05\01@153529 by Bob Barr

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On Thu, 1 May 2003 14:21:55 -0500, you 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?
>

Since the 20 nS shift is 0.00256 of your 7.8125 period, it's also
0.00256 of your 360 degrees. By my calculator, it comes out to 0.9216
degrees.
(if I've done the math correctly)

Regards, Bob

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2003\05\01@153712 by Harold Hallikainen

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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 <dbrantleyspamspam_OUTAUSTIN.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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2003\05\01@153915 by Robert Ussery

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Divide the phase shift by the period (20/7812.5 = 0.00256) and multiply by
360 (.00256*360 = 0.922 degrees), maybe??? I'm no math wiz, but this seems
right.

- Robert :O)


{Original Message removed}

2003\05\01@155412 by Duane Brantley

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Thanks guys,

I was trying to make it more complicated than I needed.

Duane

On Thu, 2003-05-01 at 14:34, Spehro Pefhany wrote:
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2003\05\01@181247 by Wagner Lipnharski

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Duane Brantley 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


Duane, math solve this easily considering delays and finding the
proportional part of 360 degrees, but, hmmm, I would go for some adventure
on this.  Why not delight upon adversity?  It is always a joy.

a) Produce a constant current capacitor charging circuit.
b) Charge the capacitor with the original full wave period.
c) Reshape the constant current value to charge the cap with 75% of total
possible voltage
d) Measure the capacitor charge with a precision ADC, store the value.
e) Dischareg the capacitor with the phase shift period.
f) Measure the capacitor again, multiply this value by 100,000
g) Divide this value with (d), finds out the percentage, with 3 decimal
digits.
g) Multiply this percentage by 360.
h) Voilá, you have the phase shift in degrees.

Difficult?

hmmm

What about this:

a) Set a precision 16 bits or more ADC.
b) Use the Full Wave period to charge a cap using constant current.
c) Use this cap voltage as Ref for the ADC
d) Use the Phase Shift period to charge a second cap
e) Read this cap voltage with the ADC
f) Voilá, the relative ADC output to Span means your 0-360 degrees.

Not yet?

hmmm

a) Produce a Frequency Multiplier Hardware
b) Set it to multiply the base sinewave frequency (your 128kHz) by 36,000
c) Use the phase shift period (delta) to gate this multiplied frequency to
a cleared counter.
d) Counter value will be showing directly the phase shift in degrees with 2
decimal digits.

Still not satisfied?

hmmm.

math?

Wagner

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