Resistance to voltage conversion circuit

Discussion in 'General Electronics Chat' started by EightequalsD, Aug 8, 2005.

  1. EightequalsD

    Thread Starter New Member

    Aug 8, 2005
    Hi everyone. I am currently working on designing a circuit which will convert a resistance value to a voltage. The design of the circuit includes the use of a bridge rectifier and an op amp which will amplify the voltage difference between each side of the bridge. Designing the bridge is fairly easy, however designing the amplifier portion of the circuit is difficult so far. Does anyone have any suggestions on what approach I should take in designing the amplifier portion of the circuit?
  2. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    Remember that E=IR?

    Therefore, if you apply a constant current source to the resistance to be measured the voltage generated across the resistor will be porportional to that resistance.

    1K * 1mA = 1V
    10K * 1mA = 10V

    Watch out for the load resistance presented by any device you attach to measure the voltage; it must be >> (much) higher than the resistance being tested or it can significantly skew the results. A very high input impedance instrumentation opamp could serve as a good output buffer.

    There are many application notes regarding constant-current sources.