Didier Juges wrote: > Dr Bruce Griffiths wrote: > >> In principle this measurement could be made with a time interval counter: >> PPS -> START >> delayed 10KHz -> STOP >> >> Vary the delay and watch the jitter jump when the leading edge of the >> PPS signal occurs during the 10KHz burst which was phase coherent with >> the previous PPS pulse. >> The only problem is finding a suitable variable delay device with >> sufficiently low (<=1ns??) jitter. >> >> >> > The delay device can be triggered by the 1 PPS, then will drive the ARM > input of the counter, so as long as the delay device's jitter is less > than the 10 kHz period, if we adjust the delay to 0.99985 second > (between the last 2 periods of 10 kHz before the 1 PPS), then the TI > counter will START on the last 10 kHz pulse before the pps, and STOP on > the 1 PPS. > Tek has some time delay generators in the TM-500 and 7000 plug-in > series. I knew one day I would need one of those, I now know why :-) > > Didier > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Didier
A much simpler/cheaper though less flexible solution to the phase jerk measurement problem. Construct a preloadable synchronous up counter using 4 74HC163's (74HC160 or 74HC162 also OK but may be harder to obtain). Clock this at 10KHz from the GPS receiver. Use a 74HC164 to synchronise the PPS output to 10KHz (use a 74HC86 as a clock buffer so the correct clock polarity can be easily selected). Use a 74HC00 to generate a pulse one clock cycle wide from the shift register 7th and 8th stage outputs. This pulse is used to load the counter chain with a suitable value corresponding to the desired delay. A decoder and a deglitching flipflop are used to generate a glitch free GATE signal for the HP5370. A 74AC04 can be configured as a suitable driver for the ARM input. Additional logic ensures that the counter resets to zero and stops until the next PPS pulse occurs. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts