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Thread: Temperature control

  1. #1
    Join Date
    Feb 2005
    Posts
    246

    Default Temperature control

    I have a electric oven and have added a CTX 3000 controller. It will not reach set temperature at 1500 F.
    It will get to 1498 but not 1500.
    I need help in setting "heating time" or on time.
    Anyone have experience with this controller?

  2. #2
    Join Date
    Aug 2006
    Location
    Beaverton, OR
    Posts
    7,184

    Default

    Does it have auto-tune? It may need to be ran to learn he parameters of the oven. Its settling time (The I of PI Loop) may be too low.

  3. #3
    Join Date
    Apr 2006
    Location
    Northwest Missouri USA
    Posts
    930

    Default

    The temperature signal is analog from a thermocouple before it is converted to digital. I don't believe it can be calibrated to within 2 degrees in 1500.

  4. #4
    Join Date
    Feb 2005
    Posts
    246

    Default

    I can't find an auto tune.
    The P (Proportional band) is currently off.
    The I (Integration time(s)) can be adjusted from 1 to 3600 sec.
    Are you suggesting increasings the I? Or will the "I" only work with Proportional band.

  5. #5
    Join Date
    Feb 2005
    Posts
    246

    Default

    The controller will hold +_ 0 then set at 500 F, so I am thinking It is not heating long enough to keep up with losses at the higher temperature.

  6. #6
    Join Date
    Feb 2005
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    246

    Default

    I can't find an auto-tune, so I think it does not exist.
    The "P" (proportional band) is off.
    The "I" (Integration Time) can be set between 1-3600 sec.
    Are you suggesting increasing the I?

  7. #7
    Join Date
    Nov 2006
    Location
    Newtown, CT
    Posts
    519

    Default

    The normal manual PID tuning procedure is to set I=0 and D=0, then increase P until the system overshoots or becomes unstable. Then reduce P until system is stable.

    If there is residual error or poor dynamic response, increase I. This will affect the dynamics (e.g. overshoot at startup) while also reducing residual error. It may take some experimenting with P and I to find the best compromise for error and speed of response. Some PID controllers have an "anti-windup" setting to limit the amount of error integrated during startup; this can help minimize the startup transient which often allows stability with higher I settings.

    D is seldom required. Occasionally it can improve response characteristics but can easily make the system unstable.

    If your oven can't get to 1500 then the PID can't do much to help. Probably best to try tuning at a lower temperature, say 1400, which you know the oven can achieve.

  8. #8
    Join Date
    Feb 2005
    Posts
    246

    Default

    I'll try your suggestions, thanks

  9. #9
    Join Date
    Aug 2003
    Posts
    871

    Default Heat System

    What type of thermocouple are you using? Do you have calibration certs for the thermocouple? Has the controller been calibrated? Two degrees in 1500 is not bad for a simple oven system.

  10. #10
    Join Date
    Nov 2009
    Location
    Somewhere between Portlandia & Salvation
    Posts
    532

    Default

    Not to derail your conversation but do you have an internet site reference for oven controllers. I'm building a powder coat oven. Thanks.

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