Hardware Installation
SCX 920 Installation Guide 23
You then select the next standard resistor, 475Ω, with a 0.1% or 1% tol-
erance. (The accuracy of the input is directly proportional to the
tolerance of the resistor. So the lower the tolerance, the greater the ac-
curacy.) The wattage rating should be greater than or equal to watt.
Be sure you check the Infinity CX Controller Programmer’s Guide for
details on how to convert the voltage from a current input to other units.
Wiring the Outputs
Wiring Tristate Outputs
The outputs are down the entire right side of the SCX 920. All output
wires should enter from the right. Notice that the first output is labeled
from top to bottom NC, C, NO, I, V, GND. The next GND starts the
second output, labeled GND, I, V, NC, C, NO.
You can wire a pair of output relays, one odd numbered output and the
subsequent even numbered output, to control one tristate output. When
you do, the odd numbered override switch controls the tristate output.
You can then use the even numbered switch to control an analog (cur-
rent or voltage) output, but not a Form C output.
(Because of this option, you can have up to four tristate and four analog
outputs on the same board.)
To set any of the four pairs of outputs to a tristate output, proceed as
follows:
1. Find the slide switch to the right of the pair of override rotary
switches. Set the switch to the down position (marked TRISTATE
on the top and bottom switches only, but applicable to all of them).
The tristate output connects to four terminations only—Common,
+ON, Normally Closed (NC, equivalent to OFF), and –ON.
2. Wire the tristate output as shown in the diagram inside the front
cover of the controller.
Figure 10 shows the diagram also.
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