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Analog I/O Module C0-04AD-2 Scaled Value

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  • Analog I/O Module C0-04AD-2 Scaled Value

    I have a IFM PX9114 Pressure Transducer attached to a closed pressure vessel. The Transducer is in the I/O C0-04AD-2 Module System Config with an Input Range of 0 - 10 and a Scale Range of 0 - 100 on CH 1 with the Data Register DF1. The Data View of DF1 shows a series of numbers in red being repeated cyclically in the Current Value field. The System Monitor shows the same pattern as Scaled values, however the Physical value is 0.0V. The Status Monitor of the Project is shows the same changing cycle of Scaled Values. The Pressure Transducer is powered by a Rhino PSP24 and a single wire to CH1 of the C0-04AD-2, which is also powered by another Rhino PSP24. Both PSs have been calibrated to 24V. There's been no pressure applied to the vessel yet.

    Is the Pressure Transducer delivering Input to the IO as a change in the atmospheric pressure? If not, what does the series of changing Scaled Values represent?
    Why does the System Monitor Physical Value remain at 0.0V if the Scaled Values are changing?
    I've written the Rung in the Project to read Data A DF1 = Data B 14.7. Data B represents the psi of the pressurized Pressure Vessel. Should the constant (14.7) be the the Scaled Valve or the Physical Value? If it is the Scaled Value, is the constant then 1/10 = 1.47?


  • #2
    A wiring diagram would help.
    Is the 0V rail of each psu tied to the analog input COM?
    What is the actual (DMM measured) voltage at the analog input?

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    • #3
      I agree with Kewakl that a wiring diagram of your setup would be helpful.

      I just did a project using an analog ultrasonic sensor to an analog Click, and even though the substrate I was sensing was not moving, the values coming in on the channel changed continually, so I had to add logic to filter the signal. Look at THIS THREAD and at post #3 Garry has an excellent piece of code that settled down the signal I got very effectively. Ignore the first two math functions and just use rung 3. Where Garry shows DF6 place your DF1 value. You can use any DF registers for the rest of rung 3, just make sure they're not already in use by other analog channels. Your result of the math function is the DF register you would use for value you monitor for the rest of your PLC code.

      Good Luck!
      Last edited by Todd Dice; 10-08-2019, 02:22 PM.
      Why worry? If you've done the best you can, worrying won't make it any better

      - Walt Disney

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      • #4
        "The Data View of DF1 shows a series of numbers in red being repeated cyclically in the Current Value field. The System Monitor shows the same pattern as Scaled values, however the Physical value is 0.0V. "

        What series of number are you seeing? you are expecting 0 so you may think anything other than 0.000 is a problem, but the CLICK is a fairly low price instrument and I have found the analog inputs to be fairly noisy. If you are seeing things like 0.024, 0.048, I'd think that is normal, if you are seeing numbers larger than 1.0 then you have a problem.

        For similar reasons;
        "I've written the Rung in the Project to read Data A DF1 = Data B 14.7."
        won't really work, computers (and micro controllers) are very literal about "equals" and value will rarely if ever be "exactly" 14.7. You'll need to decide your allowable tolerance and then do a window comparison, perhaps something like, ---[DF1 > 14.65 ]---[DF1 < 14.75]----

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