Strain gauge to op amp question

Discussion in 'The Projects Forum' started by snaker5, Nov 19, 2013.

  1. snaker5

    Thread Starter New Member

    Jan 26, 2010
    5
    0
    I am playing around with a strain gauge that I pulled out of an old scale. It is a three wire strain gauge and I have determined from the resistances between the wires that it acts like a potentiometer, the middle wire acting as the wiper. My problem is occuring when I wire up the wheatstone and then to a LM324N op amp. The wheatstone is figured out (I get 0V across the 'sense' nodes when the strain gauge has no load applied). I can't seem to get a proper output on the op amp. With a gain of 65 I get Vout = 8V with no fluctuation when the strain gauge is compressed. Vout remains at 8V even when I unplug the two sense wires and the resistors from the op amp, which makes no sense (no pun intended) to me. I've attached my circuit and would appreciate any insight to this problem. Thanks!
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,386
    496
    Why your op-amp has two inputs?

    The op-amp inverting input should only have the two resistors, nothing else.
     
  3. snaker5

    Thread Starter New Member

    Jan 26, 2010
    5
    0
    hmm Not sure what I was thinking. Problem has been fixed. thanks!
     
Loading...