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3 wire RTD sensor reading circuit

Discussion in 'Sensors and Actuators' started by jmajor817, Apr 10, 2013.

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  1. jmajor817

    jmajor817

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    Apr 6, 2013
    Hello all I am currently working on a way to get an accurate reading from my RTD sensor. Here is the link for the PT100 RTD I have already purchased.

    http://www.auberins.com/index.php?ma...products_id=96

    Here is another link of how I think I am going to get an accurate reading into my microntroller.

    http://openenergymonitor.org/emon/node/75

    I have two questions, one is kind of silly, and the other is whether or not anyone thinks this will work.

    1. on this RTD there are three wires, 2 red and 1 white, if I am using the circuit in the example shown, which wires go where into the microcontroller and circuit.

    2. does anyone have any experience with this or another option.

    Thank you for any responses.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,387
    2,772
    Jan 21, 2010
    This should explain the three wires. You should be able to use a multimeter to determine which leads are common (possibly the 2 white ones).

    I see no particular reason why the circuit you suggested won't work.

    I would use a constant current source rather than a simple resistor, but the difference is probably not worth worrying about for a small temperature range.

    If you're using that circuit, you can't compensate for the resistance of the wires. It may not be critical, especially if you're assuming the device is linear.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    Here is an application note by microchip (PIC) on RTD usage. You already have a 3-wire RTD, so I recommend you use the 3rd wire for compensation.
     
  4. jmajor817

    jmajor817

    6
    0
    Apr 6, 2013
    The temp range will be -10 - 115 C. Do you think a constant current source will be necessary for this range?
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    It'S definitely the better circuit. Asimple constant current source isn't that hard to build, as Google.
     
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