Emerson Exchange 365

HART digital signals for control or interlocks?

Assuming the update rate is sufficient:

Is it supported to use HART digital signals for control?

Is it supported to use HART digital signals for interlocking?

• Control
• interlock
• HART
• CHARMS
• DeltaV

Brian Hrankowsky

• 17 Feb 2020 6:40 PM
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19 Replies

• Jonas Berge

  

  • 21 Feb 2020 1:11 AM

  In reply to Jonas Berge:

  When HART is used for continuous polling make sure to have a "digital grade" installation as per HCF_SPEC-054 specification to ensure error free communication:
  • Shielded twisted pair type cable
  • Low capacitance type cable
  • Loop resistance
  • Cable length
  • Loop capacitance
  • Safety barrier operational parameters
  • Cable shield connection in junction box
  • Cable shield isolation in device
  • Cable shield grounding
  • Power supply ripple/noise

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• Jonas Berge

  

  • 21 Feb 2020 1:45 AM

  In reply to John Rezabek:

  @John: traditional "plain" burst mode continuously bursting (publishing) data has been available in wired HART devices for decades such as in HART5 devices and even earlier. The "triggered burst mode and event notification" were introduced in HART7 to send data (only) when something happens (not all the time). It was primarily intended for wireless devices, but some manufacturers also implemented it in their field devices. It may not be so useful in wired devices.

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• Mike Link

  

  • 26 Feb 2020 4:49 PM

  In reply to Andre Dicaire:

  At least with CHARMS they DO NOT tolerate burst mode well.
  
  We had a handful of instruments that would all quit HART comms about every two weeks, pulling and reinserting the CHARM would fix it. We eventually put a scope on the line for an instrument with non-working HART and it appeared as though the CHARM and the instrument were "shouting" at each other. Eventually looked at the instrument configuration closer and found that burst mode had been inadvertently turned on at some point. I assume DeltaV was considering the burst data as noise and turning up its transmit power.

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• Andre Dicaire

  

  • 27 Feb 2020 4:17 PM

  In reply to Mike Link:

  Mike, Your correct. This was addressed in a Firmware update for the AI CHARM such that if Burst Mode is enable, the CHARM will still function, but it still will not use the Burst communication.
  
  If you have an older firmware version in the CHARM, HART can stop working. Solution: Disable Burst Mode.
  
  If you have new Firm ware, HART should continue to work. You should still disable Burst Mode as DeltaV ignores this. If you do need Burst mode for some unique application, make sure you have latest Firmware in CHARM.

  Andre Dicaire

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