In message: <[EMAIL PROTECTED]>
Hal Murray <[EMAIL PROTECTED]> writes:
: > It also has a 1 pulse per second output; what is it good
: > for, in industry, and for me?
:
: That 1 PPS signal ticks on the UTC second boundary. That lets you transfer
: accurate time as well as frequency to other boxes.
:
: Suppose you want to build a time server. If you connect up the serial port,
: you can ask the Z3801A what time it is. The answer won't be very accurate
: (few ms) because of delays in the serial port hardware and software. With a
: PPS signal (and widely available patches to the OS) you can get that down to
: microseconds.
You can likely get closer to nanoseconds, if you know the cable delay
from the on time point of the system. We use the PPS signal in a
system at work to steer a three clock cesium ensemble down to the
nanosecond or so level. But we have specially cut cables to make sure
that we measure the PPS from the cesiums at a known offset. Going
below nanosecond level requires compensation for many other factors,
and time is likely better transferred using a higher frequency than
1Hz.
Warner
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