X-320M™ User's Manual
Installation and Setup
4-20 mA Sensors (Current level conveys information, not voltage levels)
Some sensors are designed to change the output of the current instead of the voltage levels. To use
these sensors, a resistor is placed in parallel with the sensors. Placing a resistor across the terminals of
the sensor creates a voltage drop between them that changes as the current changes. This voltage drop
can be measured by the Analog Module. The following diagram shows how to connect one of these
sensors to the Analog Inputs.
For sensors that have an output of 4-20 mA, a resistor value of 250 Ω can be used to get the desired
output voltage between 0 and 5 volts. Ensure that the size of the resistor is appropriate to handle the
power dissipation. A 20 mA sensor at 5 V will dissipate ¼ W.
Xytronix Research & Design, Inc.
Page 21
Figure 2.2e - Using a sensor with a 4-20 mA output
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