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3 wire RTD theory

  1. Apr 6, 2008 #1
    I would like to confirm the operation of a 3 wire RTD.
    The 3rd wire is a high impedence voltage measuring lead only and does not conduct. Call it "C"

    The other 2 leads we will call A and B and do conduct. The resistance of these two leads introduce a measurement error.

    My assumption is that C measures the loop voltage before the resistance of one of the leads then measures the loop with both lead resistances.

    The electronics then do a calculation which should look like this

    (A+B+RTD)-(A or B+RTD)=Resistance of A or B

    Therefore (A or B+RTD)-(A or B)= True temperature of RTD

    Seems simple but I could not find the data to confirm this anywhere on the net
  2. jcsd
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