3-30 | Thermox CEM O2/TM
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 3-24):
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.The switch settings
are:
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 at the end of this Installation
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.
Содержание Thermox CEM O2/TM
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Страница 53: ...Installation 3 31 Figure 3 24 Series 2000 4 wire RS 485 communications connections...
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