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Optional Connector Wiring Diagram
The option of connecting the module to a sensor that doesn't have the Manning interface plug is shown in the
next figure. Ensure the interface connector is securely fastened to the module and the screw terminals are tight
against a bare copper conductor.
Addressing
Each module has a Modbus address pre-programmed from the factory. See Diagram 2.
•
The 4-20mA output Modbus register is #14. It is coded as a 16-bit signed integer (PLC interface only).
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Divide the numeric value in register #14 by 100 to convert to mA (PLC interface only).
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The device responds to Modbus RTU protocol, 9600bps, 8-bit data, 2 stop bits. It supports Modbus
•
function 0x03 "Read holding registers" for a length of 1 to 35 registers. It also supports Modbus func-
tion 0x10 "Write multiple registers" for a length of 1 register only.
The procedure to change the Modbus address (using a Modbus master device such as a PLC or PC):
•
1. Write register #6 (using function 0x10) with value 144 (0x90)
2. Write register #1 with the desired Modbus address (1-247)
3. After this write operation, the 420MDBS will respond to its new Modbus address
Writing values other that those described above or writing to any other registers, may lead to unexpected be-
havior.
Faults and Alarms
Sensor faults are identified as a 0.5mA reading on Modbus register is #14 (PLC interface only).
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For PLC applications, the alarm levels are programmed within the PLC.
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For 96D controller applications, the alarm levels, ppm levels, fault status, gas type, sensor type etc.
•
can be programmed at the factory in each module upon ordering. In this case Register #14 is no
longer a 4-20mA output.
80
Figure 3.
420MDBS Optional Connector Wiring
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