Emerson Exchange 365

Foxboro CFT51 Flowmeter with Modbus

I have a CFT51 coriolis flowmeter which only has Modbus and I can connect to the unit but as soon as I add a dataset, communications go bad. The flowmeter Modbus map uses registers as an example, of 

303001 where three indicates it's read only, zero is called a separator, and 3001 is the actual value which I want to read. The problem may be in the number of digits. When I try this in a dataset, the register shows up as R33001, six digits. When I add the dataset, it goes bad in Diagnostics. Has anyone experienced this on a like or similar instrument or device?

wharnett

• 23 May 2022 2:15 PM
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2 Replies

• John Rezabek

  

  • 23 May 2022 9:41 PM

  Not sure I can be any help, but could you fill us in on the following:
  RTU / serial or Modbus over TCP/IP?
  If serial, there's interesting details like data type (integer, real, etc.) baud rate, parity, etc. Full duplex, how many conductors etc. etc.
  If using TCP/IP I'm probably less help.

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• Andre Dicaire

  

  • 24 May 2022 4:30 AM

  The DeltaV Serial card defines the registers using a 16 bit integer that limits the range in each type to 9999, in your case 30000 to 39999. You cannot address registers of any type beyond 9999, as this would be in the 40,000 range the points to Holding registers.
  
  You would use 33001 to read the 3001 address. The dataset is defined with a starting register address and up to 100 registers. The saturating value must be between 30001 and 39999, but the number of registers cannot result in an address that exceeds 39999.
  
  I’m not familiar with your device, but could 3001 actually be register 1 and therefore you should use 30001 in the dada set? I would try this. If this the case, register 3001 may not be defined and that explains why there is an error at run time.

  Andre Dicaire

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