Interfacing of Pt100 with PIC controller

Discussion in 'The Projects Forum' started by embpic, Mar 4, 2014.

  1. embpic

    Thread Starter Member

    May 29, 2013
    187
    3
    i am using pic16f876a controller and need to interface pt100 with pic. So after googling i found there is some 2,3,4-pin configuration
    for connection. so i am bit confuse to connect this pt100 with pic controller. as my pt100 has only two wire which rod type.
    so how to interface pt100 with PIC.
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi,
    Look at this data sheet pdf [last page] and the LTSpice sim circuit for options.
    Ask if you have a problem.

    E
     
  3. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,136
    200
    All PT100 sensors are 2 wire, it's the wires to the sensor that can be 2, 3 or 4.

    Since the resistance change is small, one has to compensate the lead resistance.
    In a 2 wire connection, or when the wires are short, compensation isn't necessary.

    In a 4 wire system, you can think of Force and Sense terminals. One pair may force a voltage at the sensor and the other will measure the voltage at the sensor, thus lead resistance is removed from the equation. Current is current through the circuit and in a 4-wire system, it doesn't matter the resistance of the ammeter/leads.

    In a 3 wire system, one assumes that the resistance of the wires are identical, so 2x, the drop of force wire is compensated, Saves cabling costs.
     
  4. embpic

    Thread Starter Member

    May 29, 2013
    187
    3
    thank you sir and how to interface this with pic controller.
     
  5. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi,
    You could use a variation of the circuit shown in my post #2.

    E
     
  6. embpic

    Thread Starter Member

    May 29, 2013
    187
    3
    thank you and sorry for late reply.
    circuit you provided is can measure only upto 100 degree celcius right??
    but i am looking for to read temperature upto 300.
    so what changes require for this circuit. and i think instrumentation aplifier will be strong option.
     
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