Maybe I just don't understand the process, but can't for the life of me figure out how they work.
When I am mashing out 168F and the temp on the RIMS heater shows 164F, why does the PID/RIMS heater go on and off instead of steady on?
Is it not wanting to overshoot? But 4F seems like a big gap to be shutting down.
PID - how do they work?
Re: PID - how do they work?
Here is the algorithm used by the BCS:
http://www.embeddedcontrolconcepts.com/ ... ementation
You can see the PID algorithm in action by watching the PID Output Display:
http://www.embeddedcontrolconcepts.com/ ... er_Display
You are correct, the reason that the output starts throttling back as you approach the temperature setpoint is to reduce the overshoot. This is, of course, totally programmable and system dependent. If you want your system to stay steady on longer when ramping up, give it a little more "P".
I recommend playing with a few values with a water test. Change the setpoint, and watch the system response with the datalog chart. Bump up the Proportional Gain, and change the setpoint 10-20deg higher, and watch the new system response.
http://www.embeddedcontrolconcepts.com/ ... ementation
You can see the PID algorithm in action by watching the PID Output Display:
http://www.embeddedcontrolconcepts.com/ ... er_Display
You are correct, the reason that the output starts throttling back as you approach the temperature setpoint is to reduce the overshoot. This is, of course, totally programmable and system dependent. If you want your system to stay steady on longer when ramping up, give it a little more "P".
I recommend playing with a few values with a water test. Change the setpoint, and watch the system response with the datalog chart. Bump up the Proportional Gain, and change the setpoint 10-20deg higher, and watch the new system response.