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Help with a little project I'm trying to do:

  1. Dec 27, 2007 #1
    Hello All,

    I'm planning to do a relatively simple project.

    What it consists of is a wheatstone bridge. I'm making a wheatstone bridge connection with 3 resistors and one unknwown resistor which is a pressure sensor. I know that the sensor changes from say 5,000 ohms (originally) to a maximum of 22,000 ohms.

    Now, I am trying to find 3 ideal resistor combinations of the remaining in the wheatstone bridge which would give me MAXIMUM voltage variation with just a little amount of pressure on the sensor.

    I'm trying to play around with different resistor value combinations going high/ low etc ... but when will I know when I have hit the ideal combination? Would appreciate any help for the same ...

  2. jcsd
  3. Dec 27, 2007 #2


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    Gold Member

    When you design a wheatstone bridge with the intent of interfacing with a sensor whose resistance changes wrt some physical phenomena; you start from a null condition or from a balanced condition. This is when the bridge is balanced or the voltage out is zero. It just makes it easier to measure changes in resistance of the sensor.

    For this you will need four known resistances. The extra fourth one will be used to balance the bridge. Now from this null position, any changes in resistance from your pressure sensor will cause the bridge to come out of balance.

    If you want maximum voltage variation, why not amplify the output of the bridge with a differential amplifier? Also note that you won't want a too great of a change in your sensor's resistance as this will cause nonlinearity and isn't good if you plan on making some sort of calibration curve.
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