Detcon 1600A-N1P - Manual (Page 14)

1600A-N1P
Figure 9 Model DA-4 and 4-20mA Gas Sensors
RS-485 Modbus Gas Sensors
Connect the five wires from the Modbus™ gas sensors (Detcon Model 600 and Model 700 Series types) to the
din rail mounted terminals labeled RS-485 “A”, “B”, and “Shld” and VDC “+” and “-”. Note: the controller
power supply is only capable of handling 3 Amps accumulative. If the external sensors plus the controller’s
internal modules exceeds this rating, only three wires (RS-485 “A”, “B”, and “Shld”) should be used and a
remote DC power source should be utilized to provide DC power for the remote mounted gas sensors.
NOTE: A 120 Ω end of line resistor should be installed on the last gas sensor in the serial loop to enhance
communications reliability.
Figure 10Modbus™ Gas Sensor Connections
1600A-N1P Instruction Manual Rev. 0.1 Page 10 of 40