Instruction manual

Introduction
4 025-9209
There are a variety of other status points that may be monitored: open door or window, high
water alarm, high temperature, main power, panic button for man at site, etc.
The RTU analog input range is 0 to 5 V
dc
, and the levels being monitored should be
electrically scaled to fall within this voltage range. Many sensing devices output 0 to 5 V
dc
.
However, some sensor outputs are 4 to 20 mA current loops, or an input may be using a 12-
volt power supply. The diagram below shows how to convert these two power sources into 0
to 5 V
dc
levels for the RTU (4-20 mA Loop would be converted to 1-5 V
dc
). There is a 249 Ω
resistor in the RTU that may be used to convert 4-20 mA to volts.
470 kΩ
Analog
Input
12 Vdc
Power Supply
330 kΩ
Analog
Input
249
Ω
4 - 20 mA
Loop
Figure 4. Common Conversion Circuits for 0-5 V
dc
Scaling