
VOC Pro Transmitter • 69
For more information on properly wiring a daisy chain network of devices for Modbus,
consult the following diagram.
The signal wire of each unit is run to the signal terminal of the neighboring sensor. With each
device connected to the previous device via the signal wire, a “chain” is created, with the first
device in the chain directly connected to the controller.
(*) Terminating resistor may be required for the last device in the daisy-chain.
RS-485 Modbus Connection Distances for Electrical Wiring
Distance
Length
Gauge
Size
Twisted Pairs
Short
< 100 Feet
22 to 24
Gauge
Shielded, in areas of
high noise
Medium
101 Feet to
1,000 Feet
18 to 20
Gauge
Shielded, in areas of
high noise
Long*
1,000 Feet to
4,000 Feet
18 to 20
Gauge
Shielded, in areas of
high noise