Ok, I'll bite. For all you tech types here are some of the sources of
timing errors. I'm sure this list can come up with others:
1. Variations on what part of the car trips the lights.
2. Variable trip delays between start lights and stop lights.
3. Capture window granularity associated with polling for light trips.
4. Variation in time based frequencies, eg, a crystal oscillator is more
stable than a cheaper ceramic resonator and crystals themselves come in
various grades.
5. Drift and variation caused by voltage and temperature fluctuations over
the course of the event.
I suspect that our current system is much more accurate than the old Radio
Shack encoded, white light timing head based system that actually had a
relay in each head with all the variation attendant from a mechanical relay
closing. I bet that system was only accurate to around a tenth of a second
and bet our current system is accurate to around a hundredth of a second or
a smidgen better. For those of who think it's accurate to a thousandths of
a second; dream on, and I don't mean Steven Tyler.
-- Rick
-----Original Message-----
From: owner-ba-autox@autox.team.net
[mailto:owner-ba-autox@autox.team.net]On Behalf Of John Kelly
Sent: Friday, May 28, 2004 4:48 PM
To: groups@pursued-with.net; Richard Urschel
Cc: ba-autox@autox.team.net
Subject: Re: How accurate are our timers?
I think the timers we have --JA Circuits--are outstanding. At a recent
event I matched my time down to the .001 of a second. I'd never done that
before, not even when we had the Manzanita three channel or four channel,
or the old gas station bell ringer rubber hose as a trigger.
In the latter era the timers also magnetized themselves and ran
slower in the afternoon. There were timers that used hand-aound stop
watches in that era. The early electronic timers used lights alongside
numbers, only to the second decimal. Later came Nixie tubes to show an
actul number, but only to the second decimal. One of our guys in the era
held an EE degree from Stanford and sold us his brand of timer. He also
pointed out the electric power line on the fence at the Pleasanton
Fairgounds did not deliver a full 110 volts and that was another reason for
wobbly times. We've come a long way.
Our present timer's eye is located several inches above the surface
and is quick enough that the timer catches the lightbeam breaking by the
tire. Early electric eye units were much slower to react than our current
units. A chrome wheel at that time could not be "seen" by those eyes.
--John Kelly
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