Linear Equation using opamp; 0.4 to 3.6 V FSR to 0-3.3V scalling circuit

Discussion in 'General Electronics Chat' started by Manjunath CV, Sep 25, 2008.

  1. Manjunath CV

    Thread Starter New Member

    Sep 25, 2008
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    want to convert an output of one of the module whose full Scale Range is 0.4 to 3.6V ... this needs to be scalled to FSR 0 to 3.3V ... when corellated this gives a linear equation Vout = 1.03125 * Vin - 0.4125, i can use the VCC to be between 4 to 5V, how can this be implemented using Opamps. with an error budget of 20mV max
    Rgds,
    Manju
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    If you want to minimize the offset errors then you have to use precision op-amps. They are designed to have low offset voltages. Also, for better results use resistors with an accuracy of 1% or less.
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Using 1% isn't even going to help him.. His total 'error budget' is 20mV. Due to gain error alone, assuming about a gain of 1, he can be off my 2% not assuming anything else. (2 resistors, each going away from eachother), 2% of about 3V is 60mV.

    He needs 0.1-0.2% resistors with good tempco if he wants accuracy over range. This is just one factor for a circuit like this.

    Steve
     
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