Max, Input Impedance for ADC?

4 thoughts on “Max, Input Impedance for ADC?

  1. I have looked in all the documentation and cannot find what the recommended maximum source input impedance for the ADC on a GE864 can be.

     

    Any information on this would be appreciated.

     

     

     

    1. Hi Dan,

      we didn’t declare it since it is not measurable; it is a CMOS input so impedance is very high. I just measured it in some way supplying 2V to the input trough an ampermeter and I read 0 with a scale of uA so current is less then 1uA.

      I believe source impedance is not relevant.

      1. I have read that it is relevant with ADC’s (I am new to this, so not an expert).

         

        I am trying to use a voltage divider to read the battery level, but when I use higher value resistors to limit current drain, the ADC reads inaccurately.  I was trying to find the right compromise.

         

        I may try to add an op-amp voltage follower to the input.

        1. Indeed a too high source impedance will give errors if a direct charge capacitor is in front, a CMOS buffer will make things better. To be safe, if error measurements are seen with a particular source, a follower as you said is to be put in place.