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Analog Input - HART_FIELD_VAL "Device Units Invalid" Error

On analog inputs (CHARMS), I am trying to use the HART_FIELD_VAL as the DST parameter.  I am getting Bad PV errors and in diagnostics the Status on the Channel says "Device Units Invalid".

I have HART enabled on the CHARM and have autosensed for HART device.  All of that looks good.

How do I reconcile the units mismatch and eliminate this error?

Greg Bayne

5 Replies

  • Matt Forbis
    When using HART_FIELD_VAL, it uses HART to reconcile the XD units and scales after downloading the module. If you have a disagreement between units (for example, deg F and °F are not the same unit), and the device cannot reconcile the difference, it will give this error. If you have a Trex or AMS, you could look at the device to see what the units in the device are and configure the XD_SCALE to be the exact same.

    If I recall correctly, there are two special units 'no units' and ' ' (That's a single space) that can be configured and they will always read the units from the device into DeltaV and should eliminate this error as well.
  • Greg Bayne

    In reply to Matt Forbis:

    Thanks for that. I believe I have used that method in the distant past. Should the L_TYPE be set to Direct?
  • Matt Forbis

    In reply to Greg Bayne:

    If using HART_FIELD_VAL and your Instrument is configured to the same range and units as what the control module desires, then yes, the L_TYPE is direct. If you were wanting to rescale or present in a different unit (for example, inH20 for a tank level but want to show in %), then you can still use indirect and the function block will scale linearly.
  • Tinh Phan

    In reply to Matt Forbis:

    Just to add on to what Matt have mentioned. You will need to do two module download. When you download it the second time, it will read the device scale and unit and display it and want a confirmation.
  • Greg Bayne
    The help and suggestions worked great. Thanks for the support!

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