[time-nuts] Question about an HP5370B TIC

[Bob Smither]

Dear Group,

I recently obtained a used HP5370B.  Running through the operator checks 
in the Operating and Service Manual (figure 3-4) it seems to be 
operating perfectly.

I am trying to use it to compare two 1pps signals - one from a GPS 
receiver and one derived from a fairly decent 10MHz OCXO.  The GPS 
signal is applied to the start channel and the derived to the stop channel.

As long at there is always a positive or always a negative time 
difference between the two 1 pps signals the result makes perfect sense. 
  There appears to be about a 2 to 3 usec jitter in the 1pps from the 
GPS (this is expected given the design of the receiver).

If I put the 5370B in the +/-TI mode I expected to see both + and - 
small time differences when the two signals are closely aligned - and 
mainly I do.  Typically the difference is + or - a usec or less. 
Occasionally however the 5370B displays very near to a +1 or -1 second 
(999.999 xxx ms or -1.000 000 xxx s for example) reading.  Needless to 
say this plays havoc with trying to measure a mean value of the 
alignment.  The 5370B is clearly measuring the "outside" between the 
pulse pair when I want it measure the "inside" (or short time interval) 
between the pulse pair.

Is this normal behavior?  Is there a setup that I am missing to make it 
do what I want?

Thanks for any insight you might give me!

Best regards,

-- 
Bob Smither, Ph.D.                                       Smither at c-c-i.com
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      "Liberty means responsibility.  That is why most men dread it."
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Circuit Concepts, Inc.                                        281-331-2744
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