Re: Remote VCO test/PID servo revistited

[Nick Beser <beser@aplcomm.jhuapl.edu>]

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.

Nick