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Re: Remote VCO test/PID servo revistited
On Thu, 29 Oct 1998, Chris Albertson wrote:
> Your table will be good for the APL telescope as long as the
> temperature in the computer case stays the same. So for a given
> VCO setting the scan rate is a function of the office air temp.
> This is if you keep your computer powered up 24x7 as I do so
> you don't have a warm up period to wait through.
Our system is operated in a climate controlled room, so it should be stable.
> The next part is harder. You have to continouly look at the scan
> line rate and adjust the VCO to keep the scan rate on target. This
> is not importent in an office environment but my computer is kept
> in an unheated outbuilding where is can get down to ~50F at night.
> The hard question is when there is an error in the scan rate how
> much do you adjust the VCO? Do it to much and you get ocilation,
> to little and you are unresponsive. Your chart of VCO v. scan rate
> will be a big help. I'll assume all Mk III systems have a similar
> slope on that chart. The slope should tell me how many VCO steps
> are required to correct the error in scan rate. I'd apply say,
> 75% of the required corection.
Chris, right now, we set the vco before we start data collection. If we
periodically set the vco (once every 5 minutes), it should be OK.