Hal Murray wrote:
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.How are you collecting the data? If each sample gets to a PC, you can fix it up in software.If X > 0.5: X = X -1.0 If X < -0.5: X = X+1.0One disadvantage of that is that those samples eat 2 pairs of pulses so you are only getting half as as many samples per hour.
I don't have it recording to a PC yet. Actually, my order of GPIB cables came today! I have an old ISA bus GPIB card, just need to get a minimal Linux install up and should be able to talk to the 5370B (and other instruments I have).
I like John's suggestion of triggering one side off the other edge of the pulse.
Yep. See my other response. That works fine for now.
Is the pulse from the OCXO supposed to be synchronized with the GPS second? If not, just zap the counter to move the pulse around within the one second window. (I'm thinking of shorting out one of the counter bits with a screwdriver or clip lead for a fraction of a second.)
:-). I actually have a SPDT switch that I can move one of the counter decode taps with and slew the edge with some control.
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