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  1. #1
    Join Date
    Apr 2005
    Location
    Australia : Queensland
    Posts
    817


    I come across this problem today

    On a main board

    i have 3 thermocouples on a refrig system

    1 is ambient , 2 is defrost , 3 is condenser

    if these were in the wrong position on the board , how could i tell with electrical equipment (multi meter
    not trial and error)
    where these probes should be on the board.
    The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.

  2. #2
    Join Date
    May 2004
    Location
    Caldwell, ID
    Posts
    395
    They give off a millivolt signal, but it is not linear, so just hooking it up to your DVM may not be all that useful.

    Is there any way you could pull the reading end out for each probe and put it in an ice bath? This would at least give you a reference temperature.

    At the board end measure mV for each one.

    I would guess though that the root of your problem is that you CANT pull them out.

    If you got to OMEGA.com, I think you can pull up their TEMPERATURE handbook. In the technical section, they have the equations to turn mV to deg F or (C) for various type of thermocouples.

    It is a 6th order polynomial, so it helps to use excel.

    Or you can buy a loop calibrator that reads thermocouples for 400 bucks or so. Omega has them as well.

    The link below is a Type K data sheet. Other type data sheets are available.

    http://www.omega.com/temperature/Z/pdf/z204-206.pdf

    Good luck.

    [Edited by clydemule on 02-11-2006 at 01:40 AM]

  3. #3
    Join Date
    Apr 2005
    Location
    Australia : Queensland
    Posts
    817
    here is a picture of the board in question

    The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.

  4. #4
    Join Date
    May 2004
    Location
    Caldwell, ID
    Posts
    395
    Is that a Carel controller? Made in Italy.

  5. #5
    Join Date
    Apr 2005
    Location
    Australia : Queensland
    Posts
    817
    Yep it is a Carel controller Made in Italy

    if i was 700km from the nearest town

    no phone

    just the tools in my truck

    there were no probes on the board when i got there

    no wiring diagram

    how do i tell where they go

    i know it can be done by trial and error
    but what if i had to get it right first time ?

    I think it might be possible to trace the circut back to the relay ?

    what would you do ?
    The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.

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