[time-nuts] Is my Cs C-Field set OK or do I need to take more data?

[Brooke Clarke]

Hi:

For the last few days I've been tweaking the C Field setting on a FTS 4060/S24.  Here's some data taken using the 1 PPS output of a GPS disciplined Rb oscillator (PRS10) as the "A" trigger input to an SR 620 TI counter.  The "B" stop input is the 1 MHz output from the Cs source.
http://www.pacificsites.com/~brooke/pdf/sn1013_C-Field.pdf

The plot Y-zxis is ns of Time Interval and the X-axis is seconds of run time.

A linear fit line has the equation
ns of TI = 0.0059X + 30.283.
Since this is ns/sec the drift rate of the Cs is 5.9E-12. 

So when measuring against a GPS based reference is is fair to say that you need to measure until the TI gets above something like 200 ns or the elapsed time exceeds some number? Or do I need to take more data before I change the C-Field setting?

The scale factor for the /S24 Cs units seems to be closer to 1E-13 per count than to the manual number of 2E-14 per count.

Have Fun,

Brooke

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