wrote:
Mike Monett wrote:
wrote:
.... and someone wrote
So, what degree of accuracy are you really needing?
1/60th of a second...
(ie: When the 2 hour, 53 minute, and 37 second point is reached, the
display should show it at exactly that time at an accuracy of 1/60th of
a second from when the clock started running).
....
You have no idea what your requirements mean. A drift of 1ppm in 6 hrs is
meaningless in a marathon or other race, when the wind can easily cause
1% change in performance.
....
I've been trying not to get into the details, because details lead to
the request for more details, and this is just way to complex to get
into here. Not just as far as what I'm doing, but the timer I am
seeking is actually inadequate for all of the experiments I want to do.
You will waste a lot less of everyone's time if you just go ahead
and explain what you want. If you happen to know. Of course if you
don't know what you want, you are less likely to get it.
Anyhow, AIUI you have a video game and you want to use a timer for
doing something related to this game ... perhaps you want to reverse
engineer it, perhaps crack some protection, perhaps set up a computer-
aided play device. Whatever. And you think that having a timer with
1/60 second accuracy displaying the current time throughout a six hour
period will help you do so. (It may be silly for you to think so, because
if you are just reading the time off the running display or pushing
buttons to record the time when stuff happens, you won't be able to do
either one with 1/60 second reaction times anyway.)
Note that the clock in the video game almost certainly will drift
around in a range at least 10 parts per million wide, which makes
your 1 ppm requirement superfluous. Instead, snoop the video game
clock and use a buffered copy of it to drive the counters in your timer.
This way your displayed time always is in sync with the video game time.
Now if this is so difficult to understand, then the more complex timer
will be near impossible to explain.
Perhaps your problem is that you don't know what you are doing.
Feel free to convince us otherwise.
For this project there will be 1,296,000 increments over the course of
6 hours. I just need the option of *visually* seeing on the timer's
display when each second increments beginning with the press of a start
button, and the accuracy must be 1/60th of a second at worst for any of
those 21,600 seconds after zero.
As several people have noted, you could use a TXCO (temperature
compensated crystal oscillator) or a crystal oven for adequate
performance. See eg $4 and $18 items
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526666127
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526612301
Note that you can get an inexpensive counter/timer on ebay, like
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526025102
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526108906
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526165454
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526085126
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7526393893
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7525744632
The bench instruments probably have 7 to 10 digit stability
when warmed up and similar accuracy when in cal. Some of them
might make their timebases externally available and/or have
totalizer functions that would do the job for you. In any case,
if you build a TXCO you'll need a counter/timer to check it.
-jiw