Hardware Installation
22 SCX 920 Installation Guide
Figure 8 shows a voltage sensor wired to an input point.
Figure 8. Wiring Diagram for Voltage Input
Figure 9 shows a current sensor wired to an input point. You must set
the reference resistor switch to OUT for a current input. Then wire a
resistor across the input.
Figure 9. Wiring Diagram for Current Input
The exact number of Ohms resistance required varies based on the range
of current—while we recommend 475Ω for a 0 to 20 mA input, you can
also calculate the appropriate resistance with the following formula:
To account for the input current rising slightly above the maximum
(such as slightly over 20 mA), you should choose a value slightly below
the maximum resistance you calculate. For example, you calculate the
resistance for 0 to 20 mA:
1 (input point 1)
RET (return)
V
+
–
1 (input point 1)
RET (return)
R
L
= 475
Ω
with wattage
rating
1
4
---
Watt
≥
R
max
V
IN
V
I
max
mA
-----------------------
1000×=
R
max
10
20
------
1000× 500Ω==
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