[time-nuts] How do I measure oscillator frequency using 1pps?

Bill Janssen billj at ieee.org
Sun Jul 10 11:21:22 EDT 2005

Poul-Henning Kamp wrote:

>In message <42D039CA.6030601 at onetel.net>, David Kirkby writes:
>>I've now got
>>1) Stanford PRS10 rubidium standard
>>2) Motorola M12+ timing GPS receiver with a 1 pps output.
>>3) HP 5370B time interval counter.
>>I'd like to look at the drift of the rubidium before I try to steer it 
>>with the PLL. Can anyone explain how to do this with the 5370B?
>M12+ PPS output to "START" input
>PRS10 10MHz output to "STOP" input
>Measure time intervals.
>You will need to normalize for cycle uncertainties, but that should
>be pretty straight forward.
>If you divide the 10MHz down to 1 MHz or 100kHz you will not have
>cycle uncertainties.
The setup I used when I was doing similar things was to use a lower 
frequency. I divided down the signal
using a divide by two as the last divider. That gave a square wave to 
the 5370. I used a
computer to gather the the data and control the 5370. If the reading was 
greater that 90 % or less that
10% of the signal interval I would change the triggering polarity of the 
5370. I would
also correct the reading obtained, by a suitable amount and store that 

That scheme would allow for long test intervals without  the necessity 
of correction for "roll over"
of the data when I put it in a spread sheet or plotted it out.

Bill K7NOM

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