On 3/28/12 1:28 AM, Jim Palfreyman wrote:
So when a member of the general public says:
Why do we need really accurate clocks?
Not necessarily at "time-nuts" performance, but here's some clock and
clock distribution applications
There are a lot of systems out there that timestamp something going in,
and somewhere else, it gets timestamped going out, and the difference
determines how much you pay.
Parking lots are a good example. You need to have all the timeclocks
synchronized, so that people are charged the right amount
Automated speeding ticket generators on tollways compare timestamps of
passage through the toll station with measured distance to determine
average speed.
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What's interesting is that a lot of things inherently depend on ppm
kinds of timing accuracy that you wouldn't expect.. 10ppm is 1 second
per day drift, and most inexpensive quartz oscillators aren't that good.
50-100 ppm is more typical. While 1 second isn't a big deal, but 30
seconds over a month might be, and 5 minutes in a month is a problem
(you'd hate it if your DVR started recording your program 30 seconds
after it started)
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