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Relationship between temperature and voltage of Type T thermocouple

  1. Nov 15, 2007 #1
    I have a friend who was asked what temperature corresponds to an output of 1.5mV from a type T thermocouple.

    What is the relationship and how do you get the relationship? This is an academic problem, so datasheets aren't really the answer I'm looking for.
  2. jcsd
  3. Nov 15, 2007 #2
    you could calibrate the thermocouple.
    put it in iced water, along with another thermometer. read the mV's and note the temp
    then boil the water, read the temp, note the mV's.
    i think the response is linear, but it may not be.!!
  4. Nov 15, 2007 #3


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    Staff: Mentor

    The might help - http://www.omega.com/temperature/Z/pdf/z223.pdf and 1.496 mV corresponds to 99°F (37.2°C).

    It looks like it's supposed to read ~0 V at freezing or ~32°F.

    I would recommend what phlegmy suggested. Try it in ice water and boiling water as a test.

    Type T (Copper Constantan) thermocouples.

    The Principles and Methods of Using Thermocouples

    http://srdata.nist.gov/its90/download/type_t.tab (in Celsius).

    Looking at this last dataset, 1.5 mV is between 1.486 and 1.528 mV, which correspond to 37 and 38°C, so 1.5 mV ~ 37.5°C (99.5°F)
    Last edited: Nov 15, 2007
  5. Nov 16, 2007 #4
    The output of a thermocouple depends on the temperature of the termocouple ( the point where the two wires are joint ) and the temperature where the two wires connect to the circuit ( the "cold junction" ). The output is a function ( linear ? , I dont know ) of the difference of temperatures. So there is no answer to your question.
  6. Nov 16, 2007 #5


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    Science Advisor

    It depends on the set up. Most TC systems have a cold junction compensation function. However, the OP should specify what the actual set up is. If there is a bare bones set up, the cold junction compensation is likely to be forgotten. Then the tables will be useless.
  7. Nov 16, 2007 #6


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    Gold Member

    Also, the purity of the metals in the TC will make a difference in the potential it produces.
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