[time-nuts] T.I. experimenting - newbie question
bruce.griffiths at xtra.co.nz
Sun Apr 3 01:54:31 UTC 2011
Joseph Gray wrote:
> I have a borrowed HP 5328A with the Universal Module. I'm using
> averaging mode and auto triggering. Counter does not have the OCXO
> option. I'm using the internal oscillator, not locking to my GPSDO.
> I was just messing around with a length of Belden 9273 and the 100 KHz
> square wave output from my Spectracom distribution amp. Start signal
> is the 100 KHz signal. Using a tee, the stop signal is the same 100
> KHz after passing through the length of coax. I'm reading 18.9 ns. The
> coax specs give a VOP of 66%. This should calculate out to a length of
> 3.74 M. When I measure the coax, I get 3.8 M.
> I am including the BNC connectors in my length measurement. If I
> subtract them, I'm much closer to my calculated length. Should the BNC
> connector lengths be included or not? Or, is the measurement I'm
> getting as good as it gets with this HP counter?
> Joe Gray
The measured delay includes the time offset between the start and stop
This is unlikely to be zero, you need to measure it and subtract the
offset from the measured result.
Since the 5328A can only measure positive time intervals measuring this
offset is somewhat tricky to do.
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