Offset voltage on analog output

Discussion in 'General Electronics Chat' started by azngeek, Sep 15, 2008.

  1. azngeek

    Thread Starter Member

    Jul 22, 2008
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    0
    Hi there, I have a pressure sensor that can read from 0kPa to 100kPa, giving 0mV, to 40mV. I would like to produce an offset in such a way that 50kPa, is at 0mV instead of 20mV. Any recommendations?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,650
    2,348
    Hello,

    You can use a summer as descibed in this part of the Ebook.
    http://www.allaboutcircuits.com/vol_3/chpt_8/8.html
    When you add a negative voltage you will subtract it from your signal.
    You can amplify you signal with the same circuit.

    Greetings,
    Bertus
     
  3. azngeek

    Thread Starter Member

    Jul 22, 2008
    20
    0
    Thanks for the quick reply Bertus. Just out of curiosity though. How practical would it be to use the summer circuit in series with a precision instrumentation amplifier? To get the second part of the voltage that is to be summed would it be alright to tap it off the sensors power supply? The sensor will be on a 10V regulated DC.

    So this is what I was thinking. Connect the precision amplifier to produce a negative voltage, then followed by a summer in series for the calibration.

    And this might be unrelated by after that for the A/D tap it off the same power supply to get 5V in a potential divider configuration, or should I use a sepate power source.

    Thanks again
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,650
    2,348
    Hello,

    There are special reference IC's. These give either 2.5 Volts or 1.2 Volts dependend on model.
    A voltage divider will supply the voltage you can subtract.

    Greetings,
    Bertus
     
  5. azngeek

    Thread Starter Member

    Jul 22, 2008
    20
    0
    Assuming the current leak to the op amp input pin is minimal I think using the voltage divider would work off the voltage regulator supply(LM317)

    Thanks Bertus, You've been an awesome help, haha these forums definitely are quite awesome! :D
     
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