[time-nuts] How to measure Allan Deviation?
didier at cox.net
Mon Oct 23 22:58:34 EDT 2006
Dr Bruce Griffiths wrote:
> Didier Juges wrote:
>> I do not understand the signal on the rear trigger outputs. At the
>> moment, I have a single 10 MHz sine signal fed to the START channel, and
>> the 5370 is set to TI, MEAN, SAMPLE SIZE 1, + TI ONLY, START channel
>> triggers on rise and STOP channel triggers on fall, and START COM is
>> selected. The instrument displays about 60 nS (fairly stable, 150 ps
>> jitter) or so at the moment. The rear START trigger shows a negative
>> going pulse (400uS wide, at 62 mS rep rate), with the rising edge
>> (positive going) synchronous with the 10 MHz signal and the phase is
>> adjustable using the *STOP* trigger level! When I trigger the scope on
>> the falling edge of the START trigger output, the 10 MHz signal seems to
>> drift, and the trigger setting has no effect, except that if adjusted
>> too far, the instrument stops updating the display.
>> Apparently, the START trigger adjustment has no effect on the timing of
>> the rear START trigger output, but will cause the display to freeze if
>> the START trigger is set to either extreme, even though the START
>> trigger output on the rear does not change.
>> The STOP trigger output works the opposite: it responds to the START
>> trigger level. Could it be that the outputs are reversed on my instrument?
>> I am not sure this is a complete description, and maybe there is an
>> obvious answer that I am missing, but I am perplexed.
> The 5370A processor can swap the front panel START and STOP inputs over
> via an ECL multiplexer on bord A22.
> The rear panel outputs reflect the actual selected START and STOP events
> not necessarily the signals connected to the front panel START and STOP
Good catch, but I thought that only came to play when +/-TI was
selected, and I have selected +TI ONLY?
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