[time-nuts] Why are 1PPS signals so skinny?

Tom Van Baak tvb at LeapSecond.com
Tue May 15 00:21:35 UTC 2012


Mark,

I too once preferred 50% duty cycle 1 Hz signals because they seemed more "natural". But one day during an experiment where I was comparing a large set of clocks I noticed my lab's digital AC power meter was jumping by tens of watts every second.

When a dozen DUT generate 1PPS along with as many REF pulses (via cascaded pulse distribution amps) and then these all go to both inputs of a TIC and there's also LED's on both TIC channels as well as the dist amps, the net load is enormous. The last thing you want in a precision timing lab is to load your AC line down exactly once a second. Remember 5V into 50R is 0.1 Amps. That was a modest amount of current in the 1950's, but massive overkill today.

So that's why I now prefer short (e.g., 1 ms or 10 us) pulses.

/tvb




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