|
|
|
|
Can I regulate my quartz watch?
In article ,
(Fred McKenzie) wrote:
1. Do quartz watches commonly have an adjustment for regulating them?
Some of them have a small "trimmer"; some do not.
2. How can I pick up the signal from the quartz oscillator and count it?
So far I've been unable to pick up a signal with a simple loop. I assume
such a signal is at 32,768 Hz, and that it must be amplified to drive a
counter. The trouble I see, is that one Hz error at this frequency
corresponds to a significant error over time.
You're very unlikely to be able to use any kind of frequency counter to
measure the oscillator with sufficient accuracy. There are close to a
hundred thousand seconds in a day. Measuring to one part in 10^5 will
leave you with an error of half a minute a month; not very good at all
for a timepiece these days.
Just compare the long-term rate of the watch with a good network time
server or WWV, and make slight adjustments every week or so until you
get things dialled in. By going to longer and longer "integration
periods" you can approach any desired accuracy. That method has the
advantage of not intruding on the normal operation of the oscillator in
even a slight way. And yes, it matters, especially for those
low-frequency "tuning fork" cut crystals.
Then you'll find out that those watch oscillators are just not that
stable to begin with. Temperature and even orientation effects will
become obvious, as will drift due to voltage change. Not only is the
crystal warmer when it's on your wrist, but so is the rest of the
circuitry. That will change the gain of the oscillator, and so affect
the frequency. Most of those oscillators depend upon the (relatively)
stable temperature of your wrist for decent performance, so be sure to
wear the timepiece for your "normal" number of hours each day while
you're "calibrating" it, or you won't get it right, long term.
Isaac
|