3-32 | Thermox TM 2000 Oxygen Analyzer
4-wire connections
The connections used for the RS-485 4-wire communications on the wir-
ing card are labeled as follows:
4WTX+/2W+
4WTX-/2W-
4WRX+
4WRX-
Connect all control unit 4WTX+, 4WTX-, and all 4WRX+ and 4WRX- con-
nections in parallel in a daisy chain fashion. Make the following con-
nections between the host computer and the controller in a daisy-chain
fashion (see Figure 3-27):
Host Computer TX- to Controller 4WRX-
Host Computer TX+ to Controller 4WRX+
Host Computer RX- to Controller 4WTX-
Host Computer RX+ to Controller 4WTX+
Be sure to use twisted-pair cable for all connections.
4-Wire Termination Resistor
The Series 2000 Control Unit is equipped with termination resistors that
can be used for the last control unit on the network.
SW1-1 = ON
SW1-2 = ON
SW1-3 = ON
This provides 120 ohm termination resistors in the RS-485 circuit.
See the “Option Card Installation” section in this chapter for help on how
to remove and access the display module.
You may need to experiment to get optimum performance over long
lengths of communications wiring to see if having a termination resistor
on the last control unit of the network improves communications. Re-
member, though, only to insert a termination resistor on the last control
unit on the network, and not on all control units on the network. The fac-
tory default setting is to have Switch 3 OFF with no termination resistor
in the circuit.
To Next Page
Loading...
Need help?
General