On Fri, 14 Dec 2012 00:06:15 +0100, timen...@triplespark.net wrote: >On Dec 13, 2012, at 4:57 AM, Hal Murray <hmur...@megapathdsl.net> wrote: >> Suppose I want to compare the PPS outputs of 2 GPS units. The problem is >> that I don't know which one will happen first. >> >> If I feed them into the start/stop inputs of a typical timer/freq box, I >> don't know which is which. If I get them wrong, the answer will be >> 0.999999xx seconds rather than the -0.000000xx that I want. >> >> [...] >> >> Do any of the counter/timer boxes have a mode for this? If so, is there >> a buzzword I've overlooked? >> >Counters like the Agilent 53230 actually WILL output negative delays >in this case as long as the delta is still small. This is a quite useful >feature in such cases...
I was thinking along those lines but as far as I can tell from the manual, the Racal Dana 1991 and 1992 only measure backwards to -2 nanoseconds which I have just verified with a 50 nanosecond rise time pulse and fiddling with the A channel and B channel trigger levels in common mode. I remember seeing the same thing when using a 2 nanosecond calibrated delay coaxial patch cable. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.