connecting a thermocouple to ADC

Discussion in 'The Projects Forum' started by Infinity1, Jan 11, 2009.

  1. Infinity1

    Thread Starter Member

    Jan 11, 2009
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    Hello everyone

    I need a little help in how to connect a thermocouple to A\D converter
    can someone explain me how to do it, i have written the code in VHDL and using a FPGA component and my output is 7 Segment.
    thank you for any help.
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
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    National Semiconductor's Linear Applications Hand book 2, Linear Brief 24 shows how with a LM 321 & LM308 yields an output of about 10mV/deg.C.This is old,1977.
     
  3. Infinity1

    Thread Starter Member

    Jan 11, 2009
    16
    0
    where can i find this handbook, can i download it from the web?
     
  4. Infinity1

    Thread Starter Member

    Jan 11, 2009
    16
    0
    Thank you very much, i found that handbook.
    but my question is how to connect it physically, if you have a sketch of the connection between the thermocouple to A\D converter that will be very helpful
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    If thermocouple has leads, connect one leal to -input on amp.,other lead to +; output of amp. -to ADC -, + toADC +; if reading is reversed, reverse thermocouple leads.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    It is also important to get the thermocouple leads as close as physically possible to the amp inputs. If designing a circuit board, make sure the terminals for the thermocouple leads are not at the edge of the board, but right up next to the chip. The board traces are not made of thermocouple wire and will introduce an error in measurement if they not kept short.
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    Close doesn't matter. Dissimilar metals in contact generate Seebeck voltages. Just make as few joints as possible.
     
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