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INA114: INA114 for signal conditioning of a bridge circiut

Amarnath Subramanian
Prodigy 185 points
Part Number: INA114
Other Parts Discussed in Thread: ADS1258, INA326

Planning to use INA114 for signal conditioning of a bridge circiut.
Unknown resistance varies from 0 to 1Kohms.
It will be read by ADS1258. Output of the Signal Conditioner has to swing 0 to 5V.

(Please refer the Picture attached)

When the unknown resistance is zero, output of the signal conditioner has to be 5V. But it only gives out put of 2.01V.

The Required gain is 2.


Please help to resolve the issue.

  • 0
    Prodigy 185 points

    I am trying to interface a wind direction sensor, which has a potentiometer. Its resolution is 0.1 degree (ie. 0.27 ohms/ 0.1 degree).

    I have tried with INA326 (as shown below)

    When unknown resistance is 0-ohm, it gives out put of 4.75V. (expected is 5V). with 1K unknown resistance, it gives out put of 25mV. (expected is 0V). It is giving offset of ±25mV offset.

    Please help as early as possible.

  • 0
    TI__Expert 5830 points

    Hello Amarnath,

    When R5 becomes 0 ohms the input voltage at Vin+ is set to 5V which violates the input common mode range. This is resulting in the output saturating to 2.01V in simulation. Based off a +/-5V supply and a gain of 2, the Vcm versus Vout calculator shows the highest voltage for Vin+ is 3V.

    Best regards,

    Errol Leon

    Texas Instruments

    Precision Op Amp Applications