aerl
COMMS MANUAL
COOLMAX SR
Australian Energy Research Laboratories, Pty.Ltd
AER07.004 – Version G2 v9
13
th
January 2016
6 of 21
Figure 3 – Modbus Connector
(6-Way Screw Terminal)
3.3
MODBUS WIRING
The Modbus data lines (Modbus-A and Modbus-B) must be implemented with twisted-pair wire for
proper data integrity. The wire should have a characteristic impedance of 120 Ω.
Power should also be provided along the Modbus cable, ideally with another twisted pair to
minimise noise pickup. An overall shield can also be advantageous.
Standard CAT5 network cabling (which has an impedance of 100 Ω) can be used, but may become
unreliable in longer networks or in the presence of electrical noise from DC/DC converters and other
electrical devices in the system.
Modbus Connector Socket
Important: The recommended choice of cable is 7mm DeviceNet Modbus 'thin'
cable, with 24 AWG (data) + 22 AWG (power) twisted pairs and a braided shield.
Using this cable will result in a robust installation.
B GND A
Figure 4 – Modbus Connector
Figure 5 – Modbus Connector Socket
