Chapter 2
24
Mini-Convectron Module with RS-485
Instruction Manual - 275545
2.11
RS-485 Network Wiring
Connection between multiple controllers can easily be made by daisy
chaining gauge controllers together with the signal from the host computer
going into one connector then out the other to another gauge controller.
• The maximum total cable length is 4,000 ft.
• No more than 32 devices can be connected to one RS-485
communications line.
When an RS-485 network is in an idle state, all nodes are in listen (receive)
mode. Under this condition there are no active drivers on the network. To
maintain the proper idle voltage state, bias resistors must be applied to force
the data lines to the idle condition. Figure 2-5 illustrates the placement of
bias resistors on a host computer for typical 5 volt and 24 volt systems.
Table 2-2
D type Connector Pin Descriptions
Pin number
Function
Pin 1
RS-485 + input
Pin 2
RS-485 - input
Pin 3
Input power +11 Vdc to +26.5 Vdc
Pin 4
Input power ground
Pin 6
Input power ground
Pin 10
Setpoint 1 N.O.
Pin 11
Setpoint 2 N.O.
Pin 12
Setpoint 2 common
• Factory default for setpoint 2
• De-energized P
≤
500T
• Energized P
≥
550T
Pin 13
Setpoint 2 N.C.
Pin 14
Setpoint 1 N.C.
Pin 15
Setpoint 1 common
• Factory default for setpoint 1
• Energized P
≤
5mT
• De-energized P
≥
8mT
