[time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

The most basic issue you are going to run into is that your counter is not high enough
resolution / accuracy to give you meaningful data for time intervals under a few hundred
seconds. I would focus on improving on that part of things before I went off on a major
“test everything” adventure. Simply collecting a lot of data that is resolution limited is 
not a lot of fun …..

Bob

> On Jan 11, 2017, at 9:20 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
> MY AIMS
> 
> 1) Try to learn about the various statistical tests (ADEV, MDEV etc), and
> how best to compare oscillators, by making some measurements on various
> oscillators I have.
> 
> 2) Investigate the short/medium term stability of the output of  various
> bits of test kit. All are locked to GPS by feeding 10 MHz to their timebase
> inputs, so long term drift should not be relevant.
> 
> These istrumuments are:
> 
> a) The GPS itself - primarily a test of the 5370B time interval counter,
> distribution amplifier and general temperature fluctuations in the lab.
> 
> b) Other GPS(s) when I get 1 or 2 more.
> 
> c) 10 MHz to 20 GHz Microwave signal generator.
> 
> d) 0.001 Hz to 30 MHz function generator.
> 
> e) A VNA that will work at 10 MHz. Turn sweeping off
> 
> f) A VNA that has a minimum frequency of 50 MHz. Again turn sweeping off.
> 
> METHOD - Suggestion for improvements welcome.
> 
> * Where possible set all instruments to 10 MHz, which is the same as the
> GPS reference. (Obviously since one of the VNAs will not go below 50 MHz, I
> would need to use a higher frequency)
> * Feed GPS to the start input of the 5370B TI counter and the DUT into the
> stop input
> * Use the 5370B time interval counter to measre the time difference between
> one output of the distribution amplifier and the output of the instrument
> being tested .
> * Collect data from 5370B and use John's Timelab to plot various graphs and
> try to understand the differences between the various statical measurements
> (ADEV, MDEV etc.)
> 
> MY QUESTIONS.
> 
> 1) Should I use the GPS to provide a reference for the 5370B time interval
> counter,  or would it be better to use the internal OCXO? Currently I have
> the 5370B locked to GPS too, but I am wondering if this is a bad idea and I
> should run it from its own oscillator.
> 
> 2) Is there any advantage in a 10 MHz DUT going into the start or stop
> input? I assume that it is irrelevant, as long as the GPS goes into the
> other. But maybe not.
> 
> 3) If the DUT is higher in frequency (eg 50 MHz) than the 10  MHz GPS,  is
> there any advantage in going in the start ot stop input?
> 
> 4) If the DUT is lower in frequency (eg 5 MHz) than the 10  MHz GPS,  is
> there any advantage in going in the start ot stop input?
> 
> Dave
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