Op-amp Gain vs DC offset

Discussion in 'The Projects Forum' started by snowie, Aug 28, 2010.

  1. snowie

    Thread Starter New Member

    Aug 28, 2010
    3
    0
    A big howdy to every one here.

    I've got a strain gage project I'm building and is feeding into a 10 seg led dot bar driver, and have got it working not to bad. But i need to adjust the sensitivity (gain) without the dc offset being moved as i only want to use one POT for ease of adjustment.

    Say Rail is 10v and ground is 0v. What i want to do is when there is no force applied to the strain sensor the output of the Op-amp is fixed at 5v so i can stress the sensor to go to 10v-0v. How would i do this so when i adjust the gain with no load the middle led stays on no matter what the gain is

    Thoughts would be most welcome

    Cheers
    Snowie
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Use an inverting op amp configuration and bias the non inverting input at 5V with a resistive voltage divider. You can adjust the gain by varying the value of the feedback resistor.
     
  3. snowie

    Thread Starter New Member

    Aug 28, 2010
    3
    0
    Hi Mik3

    Thanks for your reply. Would it something like this?

    Cheers
    Snowie
     
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