[time-nuts] 20221104: Help Requested Debugging SR620 Time Interval Counter Problem

[Andrew Kalman]

Hi All.

I have an SR620 that is misbehaving. I am working my way through the manual
and schematics, but one consistent behavior has arisen: At a period of
around 4-6s when measuring frequency, I get a "wrong number" that is
consistent in scale across 10MHz and 1kHz (the REF frequency).

I.e. when I measure a 10MHz signal, occasionally the display shows
9946187.4... Hz and when measuring REF (1kHz) the display occasionally
shows 994.618757 Hz. This is independent of termination, and the A & B
front-ends have passed their tests.

Has anyone encountered the same issue, or have a suggestion as to where to
look for the root cause?

[image: 20221104_SR620_SN356_Frequency_error-1-small.jpg]

[image: 20221104_SR620_SN356_Frequency_error-2-small.jpg]
[image: 20221104_SR620_SN356_Frequency_error-3-small.jpg]

--Andrew

--------------------------------
Andrew E. Kalman, Ph.D.
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