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Unable to detect the Valve Positioner in AO HART 4-20mA Charm card in DeltaV ver 12.3

I have connected a Valve Positioner to AO channel of 4-20mA Charm card in DeltaV ver12.3, I couldn't detect the device using "Auto-sense HART Device".

I have observed following error in 'Diagnose' - Diagnostics - DeltaV window,

1. Overall  Integrity value is "BAD"

2. Status is "Open Loop Detected"

Could someone help me sort out the issue? Thanks in advance.

Best regards,

Sudhagar

sudhagaran.rajaram

• 11 Mar 2019 12:01 PM
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2 Replies

• Tinh Phan

  

  • 11 Mar 2019 12:16 PM

  Open loop detected indicates that the CHARM is not having a wiring issue. Check your wiring, loop power to the CHARM. and wiring into the CHARM term block. Check book online for proper wiring and loop power for AO CHARM.

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• Andre Dicaire

  

  • 11 Mar 2019 2:37 PM

  In reply to Tinh Phan:

  The field wiring is open circuited. You are having a wiring issue.
  
  The DeltaV AO channel (Card or CHARM based) monitors the signal for an Open Loop, which means the circuit resistance is too large for it to drive the 4-20 mA signal, and interprets that as an open loop. of course an open loop is infinite resistance, right.
  
  When the CHARM has a wiring issue (either short circuit or open circuit), the red LED flashes continuously, which generally indicates the CHARM is passing self texts, but has a field side issue. Diagnostics confirms the problem with additional detail.
  
  When all the CHARMS in a base plate are flashing red, this typically indicates a common issue such as a missing Address plug. Not all CHARMs have the additional field diagnostics and some have it as a configurable option.
  
  Always refer to diagnostics for a more complete indication of issues with an IO channel.

  Andre Dicaire

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