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Program or steps to test 4-20mA output module?

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  • Program or steps to test 4-20mA output module?

    Anyone have a program to test a C0-04DA-1 analog output module? The output voltage on the modules channels are maxed and never vary no matter what I set the register values to. The unit has good voltage and ground, running the 1.4 version of the Click programming app.


  • #2
    The C0-04DA-1 is a current output module, if you are measuring the open circuit output voltage with a high impedance voltmeter it will always show a voltage nearly equal to the supply voltage. Either put a load across the output (a 250 ohm resistor will give you 1 to 5 V for 4-20mA, or a 500 ohm will give 2 to 10V) or switch your meter to current mode.

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    • #3
      Sorry for the lack of detail

      Sorry, I am measuring though a 250 ohm resistor. I have a program that sets the register values for the DA ports to 50%, should give me a 10mA output, and read 2.5v, or thereabouts, on my voltmeter. What I get is 20 volts and change.

      My program uses fill copy to populate the register values for the DA ports, DF10 though DF13. The DA module is configured as from the factory. Neither X101 or X102 (error registers) are ON. The unit has a confirmed 24 volts, but what I am assuming is a power light, in the upper left corner, does not light up.

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      • #4
        Originally posted by jt_kilroy View Post
        Sorry, I am measuring though a 250 ohm resistor.
        We may have some confusion with terminology here, are you measuring "through" (in series with) or "across" (in parallel with) the resistor?
        Resistor should be connected from the output (e.g. CH1) to one of the "0V" terminals, and the meter connected in parallel with the resistor (if using a volt meter)
        20 volts across a 250ohm resistor would be 80mA and around 1.6W, is the resistor getting really hot? (or is it a big power resistor)
        If you really are getting 20V across a 250ohm resistor the module is probably bad.

        As far as "what [you are] assuming is a power light, in the upper left corner, does not light up."
        I believe the hole is there because they re-purposed the same housing used for discrete I/O modules (which do have a power light here). While I have not used the current output modules, I do have some of the thermocouple input modules and that square does NOT light up on them.

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        • #5
          Thanks a bunch

          Hey Tinker, thanks a bunch. I was measuring through the resistor as you suspected and the impedance of my meter was throwing the voltage up real high. I should have caught that myself I do apologize. The unit is working fine now, and always was actually. User error!

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