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SOLO: does idle time affect the PID loop?

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  • SOLO: does idle time affect the PID loop?

    My Problem:
    The controller continues to pulse on/off when above the setpoint. It does this until it gets 20'-30' above the setpoint at which safeties shut the oven down.

    My Discoveries:
    1. autotune makes no difference
    2. if I change the setpoint, it starts working & controls beautifully
    3. the problem returns with long periods of downtime (overnight)

    My Application:
    I have a SOLO SL4824 controller (PID controls) operating a steam valve thru dry contacts on output #2. To turn off the oven I'm killing power to the dry contacts. The result is output #2 stays on all night. Could this affect the first oven cycle of the next day?


  • #2
    During these off times the controller needs to be placed in 'manual' mode to prevent 'windup' of the 'integral' factor. To put it another way, the controller doesn't "know" that it isn't controlling the process so it keeps raising the integral offset during this off time in an attempt to control the process. This takes a while to come back down after returning control to it, as you have seen. I don't know your controller. Check the manual for the method of placing the controller into manual mode and whether this can be done remotely at the same time the oven is turned off.



    • #3
      thanks for confirming my suspicions. Unless some guru points out a setting I'm not aware of, I'll just leave power on the output contacts all the time and turn off the oven by killing power to the SOLO unit.

      thanks again, dlp