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change kelvin to centigrade

Discussion in 'Electronic Design' started by Paul Taylor, Oct 27, 2004.

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  1. Paul Taylor

    Paul Taylor Guest

    Has any one built a circuit to change from kelvin to degrees centigrade? any help on this is much appreciated.
  2. legg

    legg Guest

    What are you starting with, a signal level or data?

  3. Paul Taylor

    Paul Taylor Guest

    Sorry, Yes I am starting with a signal level from a thermocouple chip.

    Paul Taylor BSC (Hons)
    Electronics Technician
    School of Environmental Science
    University of East Anglia
    NR4 7TJ

    Phone: +44 (0)1603 592502
    Fax: +44 (0)1603 591327


  4. Don Pearce

    Don Pearce Guest

    If you really need to do this in the electronics, simply put a voltage
    in series equivalent to the output at 0C, and of the opposite

    Far better though to get it into an ADC as quickly as possible, and do
    it with Maths.

    Pearce Consulting
  5. Bob Stephens

    Bob Stephens Guest

    It's just a fixed offset of 273 degrees isn't it?

  6. Don Pearce

    Don Pearce Guest

    Yup - 273.15 if we're being picky.

    Pearce Consulting
  7. John Fields

    John Fields Guest

  8. Tim Wescott

    Tim Wescott Guest

    This should be a simple op-amp cookbook exercise to subtract an offset
    and (possibly) multiply by a gain.

    What are you using for a cold junction that you get an answer in Kelvin
    instead of relative to room temperature?
  9. '~' is right. ;-)

    Maybe you're thinking of the triple-point (of water) = +0.01°C =
    +273.16 K

    0°C = -273.15 K

    Best regards,
    Spehro Pefhany
  10. Eric Pearson

    Eric Pearson Guest

    If you currently have a thermocouple attached to an instrument and it reads
    in K, then
    its has a cold junction compensation for 0K (which is 0 uVolts)

    To make it read in C, just add another thermocouple in series (but reversed)
    to create a
    real cold juntion, and put it in a tub of ice water at 0 C, and your
    instrument will now read in C.

    Eric Pearson
  11. Where the heck is your reference junction?
    How convenient. ;-)
    Nope. Try again. ;-)

    Best regards,
    Spehro Pefhany
  12. Rich Grise

    Rich Grise Guest

    This is every circuit anybody's built, ever.

    Degrees Kelvin Circuit o-----o Meter calibrated in Centigrade

  13. Rich Grise

    Rich Grise Guest

    What would happen if anybody ever really achieved absolute zero?

    Would the universe implode into the Final Black Hole?

  14. John Fields

    John Fields Guest

  15. Almost unbelievably cold ;-) +, of course.

    Best regards,
    Spehro Pefhany
  16. Temperature is better thought of in inverse-Kelvins. It does better at getting
    the point across about absolute zero. T usually winds up in the denominator of
    various expressions, anyway. Might as well elevate the idea to a multiplier,
    where it belongs. ;)

  17. Chaos Master

    Chaos Master Guest

    Quoting Rich Grise [], that posted to on
    Wed, 27 Oct 2004 20:52:00 GMT under article
    Would be cool for some overclocking!
    I can imagine a CPU cooled at this level.

  18. Pooh Bear

    Pooh Bear Guest

    You don't need a 'circuit' !

    Degrees C = degrees K +273

    How you choose to achieve the addition / subtraction ( either in
    software or in harware ) and input and present the data is up to you.

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