[time-nuts] And, for my next trick, 50Hz

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Oct 3 04:38:25 UTC 2008


Tom Van Baak wrote:
> measure to 1 ppm within ten seconds.
>
> /tvb
> http://www.LeapSecond.com
>
> p.s. For extra credit, tee your UUT into both channels, do twice
> the math, and see if you can measure both differential phase,
> and differential phase drift between them.
>
>
>   
Tom

A better way may be to drive both sound card input channels in phase 
quadrature with a pair of sinewave signals.
One can then any variations in calculated phase (arctan (L/R)) will be 
due to differences phase variations between the L and R channels and 
variations in the phase shift between the 2 signals.
Since 250us of delay line is somewhat inconvenient, will have high 
attenuation and will be very expensive some other means of generating 
the 2 signals in phase quadrature is required.

Corrections would need to be made for the effect of amplitude and 
quadrature phase errors.

Bruce




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