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P2K analog input problem (P2-16AD-2)

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  • P2K analog input problem (P2-16AD-2)

    We are having an issue with the P2-16AD-2 module. We can read some signals (0-10v) but not others. We checked bonding, grounding any unused channels moving the nonworking signals to different channels, checking for noise and nothing works. The problem signals are differential. Right now we are looking at the input impedance of the P2-16AD-2 module, it is only 250k ohms. I think this may be an issue with the modules ability to update its sample and hold for some signals. We are trying a P2-04AD it has 1m ohms input impedance, and if that doesn't work we will try a signal conditioner. If anyone has input I would appreciate any feedback and I will update you on what we find here.


  • #2
    I dont believe either of those modules accept differential analog input signals. The second one does allow +/-5v and +/-10v, but the wiring diagrams still show no way to connect a differential signal.

    It looks like you will need something like this to convert your differential voltage signals into non-differential:

    That unit has a V+ and V- input for differential signals and says that it can convert the +/-V into a 0-10v PLC signal.
    Last edited by MikeN; 11-29-2018, 10:20 AM.


    • #3
      The problem signals are differential.

      Does the P2-16AD-2 support differential signalling?
      Each of the P2-16AD-2's inputs is 0-10V and the common is tied to the 0V side of the controls power supply.


      • #4
        The weird thing is I can read the correct scaled voltage 6.66vdc 66% on the RTB20 pin (+) for the channel selected using the com term (-) as ground, but the P2-16AD-2 does not process the signal?


        • #5
          The P2-16AD-2 could get a value if two inputs were used with the common reference and the difference between the two signals was utilized.
          This would only work if the differential was substantial enough for the needed signal resolution.