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Sensor Input Conditioning

Discussion in 'Electronic Basics' started by Richard, Oct 13, 2005.

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  1. Richard

    Richard Guest

    I have to build a terminal board which will accept

    0-5 vdc
    1-5 vdc
    0-20 ma
    4-20 ma
    RTD

    all jumper selectable. Each channel will have 3 terminals, Grd, 12 vdc, and
    Signal. The ADC input is for 0-5 volts. I have all the voltages and
    milliamp ranges figured out with jumpering a 250 ohm precision resistor to
    ground for milliamp.

    How does one convert a RTD signal to voltage? I've tried to search but I'm
    coming up with more sales then tech info.

    Thanks,
    Richard
     
  2. PeteS

    PeteS Guest

  3. Jasen Betts

    Jasen Betts Guest

    feed it with a constant (or predictable) current and measure the voltage
    across it. use a small current to avoid heating the device.

    a large resistor to +12V would be a good start.
     
  4. Jamie

    Jamie Guest

    RTD's are resister devices.
    you have a set ohm value at a set temp.
    it simply is a resister changing it's value with
    temp..
    off the top of my head i can think of one that is 100 Ohms
    in spec.
    many devices use a current limiting source in series with
    a calibration with a RTD to supply a 4..20 ma current input.
     
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