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How do I read negative #s with an ADC

Harry Romano
Prodigy 10 points

How do I read negative #s with an ADC . Moreso what ADC in TI's arsenal  will read a positive and negative sine wave.I am trying to read a duel loadcell  that has a positive voltage when pulled and  a negative voltage when compressed.The sensor will  output a max of 5mv either positive or negative.

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    TI__Genius 12965 points

    Harry,

    ADCs typically have a comparison range when doing the analog to digital conversion.  Most ADCs will have a comparison range from 0 to 2V.  The implication here is that a signal that deviates around gnd will need to be offset to the mid point of the ADC input range.  For AC applications this can be done by using caps to AC couple the signal and then using the ADC common mode voltage to bias the signal to mid point.

    Another method is to use an op-amp to give you gain from +/-5mV to near ADC fullscale as well as provide DC offset to center the signal around the ADC input mid point.

    Regards,

    Ken.