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2.5 Modbus Validation (Continued)
2.5.1 Establish Modbus communication
Note: The Coriolis provides a Density,
Temperature and Flow output
Insure that your Modbus wires are installed correctly. Using a voltmeter,
measure between A & B terminals. Measurement should be approximately
+2.5VDC.
2.5.2 Determine Modbus Mode: Determine appropriate Modbus operating mode (either
Master or Slave) in menu 5.1. Complete the worksheet at the end of this section to use as
a reference. Function control of the PLC must be be in mode 4 [read/write] regardless of
Master/Slave setting.
If you see the following locked into the DCM then Modbus is NOT communicating with the
Density --KG/M3--
830
2.5.3 When using the DCM as a Master
If possible, confirm these settings in a workshop prior to site installation with a Modbus
simulator on a computer (in Master mode) with the PLC/Flow computer set up used. In our
examples to follow we are using "Simply Modbus" as our simulator. This will enable you
to verify Function Control is correct, what Address format (see tabe below) is required for
proper communication, as well as verifying hex values sent and received are appropriate.
If using a MicroLink RS-485 Converter, ensure the red lead is connected to "B"
on the DCM.
Little Endian Swap
Temperature --DEGC--
Address Formt Chart
Big Endian
Big Endian Swap
Littel Endian
25
Low Byte 1st, High Word 1st
High Byte 1st, High Word 1st
Low Word 1st, High Byte 1st
Low Word 1st, Low Byte 1st
17
Installation
Flow --L/MIN--
0
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