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have a environmental storage cabinet that my employer bought off the used market. It is controlled for temperature and relative humidity. Two West 6100 controllers are used. One for temp and one for RH. The temp is single output to a heater, and I have that looking pretty good. The RH controller uses dual output. One on a small electric steam generator, and the other on a compressor solenoid feeding an evaporator. The steam genny is basically a tea kettle, no control valve, just cycles the heater bar, so the response is a bit slow, and by its nature tends to overshoot. I'm not much on PID control, but have educated myself quite a bit in the last couple weeks. I have the RH control pretty close, but cant quite get it consistently within the 10% RH limits. I'm not quite using the WAG method, but a true PID expert would probably say I'm not far from it. I've used a mix of the controller manual and the Good Gain Method. As I say I'm pretty close, but not quite. My main problem is overshoot on the high side of the setpoint. I started at 0% P band overlap, and saw a regular overshoot period. This AM I put in a 10% OL. Still waiting on whether that helps or not. Anyway short story long, I'm no PID expert, so any guidance folks can spare the time for is appreciated.
