Experimental Physics and
Industrial Control System

Kathy McCormick <[email protected]> · Thu, 1 Mar 2001 11:51:45 -0500 (EST)

	Hi.  Here in Hall A at Jefferson Lab we're using the PID record
to regulate the temperature of our cryotarget by regulating the power
output of a heater. Tuesday I noticed the control behaving very oddly.  We
had set the PID max field to be 200 Watts, but the state of the target was
such that it needed 300 Watts of power on it to be regulated to the
correct temperature.  I noticed this after the heater had maxed out at 200
Watts, so I changed the PID max to 400 Watts.  The heater immediately
jumped to over 600 Watts and continued rising.  I quickly turned off the
heater, or target damage would have resulted, but I was really startled by
the heater behavior.  Has anyone seen this behavior before, i.e. when the
PID control maxes out it overcompensates when it come back?  

Thanks, Kathy McCormick

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System