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Temp Control

Discussion in 'Electronic Equipment' started by Steven McWhan, Aug 14, 2003.

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  1. Hi I need to keep a liquid at 66degrees C with only +-1'C, I have a 2kw
    heating element and at the moment i am using a strap on tank 'stat but this
    is not very accurate at all, any suggestions?

    I am in the UK so 240volts is a must and any off the shelf equipment would
    be appreciated.

    Cheers

    Ste.
     
  2. Grant Erwin

    Grant Erwin Guest

    You are likely using a "bang-bang" temp controller, the kind that
    shuts off when the temp reaches a setpoint and kicks back on when
    it goes below another setpoint. There are problems with overshoot
    on these systems as well as the inevitable hysteresis band (i.e.
    the "dead zone" between the setpoints). What you need is a PID
    controller. "PID" stands for "proportional integral derivative"
    and it essentially chops the power to the heating element a whole
    bunch of times and then controls the duty cycle using a sophisticated
    algorithm that forces the error towards zero over time. I'm not
    sure what you mean by +-1'C (is this plus/minus one degree Celsius?)
    but even a cheap PID controller should have no problem with this
    switch. 240 should be no problem. Try http://www.omron.com they
    have lots of products that can work for you.

    Grant Erwin
    Kirkland, Washington
     
  3. John Jardine

    John Jardine Guest

    Farnells do a versatile, 'Carel', digital display, temp' controller part No
    645-345 at a surprisingly cheap £43 +Vat.
    I use one in an oven for electronics testing and can attest to the stability
    of the controlled temperature.
    regards
    john
     
  4. Thanks all for your help, farnells have sorted me out.

    Regards

    Steve.
     
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