Working with 4-20mA Sensors

EA800-ip can be programmed to read 4-20mA sensors.

CAUTION! Board damage can occur if wired incorrectly.



Quick Notes 

Power should typically be supplied from the Power AUX from the EA800-ip

If a 4-20mA sensor requires external power, a common ground to Power AUX (-) is needed 

All 4-20mA sensors will ONLY tie into the Sensor Input (-)

No wire will ever need to be put into the Sensor Input (+)

Select a power supply and sensor that will be compatible with a loop resistance of at least 150 Ohms.




Use a multi-meter for troubleshooting. 

The voltage reading should between 0.6VDC to 3.0 VDC between AUX(-) and the Sensor Input(-).
Anything above this could damage the internal circuitry

Readings out of these ranges will typically read No-Data on Insight,
regardless if the EA800-ip shows a valid reading.


Steps for adding a 4-20mA sensor

1. Know your sensor. Gather information such as the full range of the probe and resolution. You will need these to program the sensor into the EA800-ip. A spec. sheet will generally give you all the information required. The 4mA and the 20mA values are based upon the scale Minimum and Maximum. Thus a humidity sensor that reads between 0% and 100% would be 4mA = 0.0 and 20mA = 100.0.

Some specs are vague and thus harder to setup, communicate with tech support if you run into issues with programming your sensor.

2.Wiring can be complex or very simple. We will show two very different setups, HX93BC and the HX71. Both of these are Omega Humidity Sensors. Power requirements must be followed carefully. If the required sensor voltage exceeds the EA800-ip supply voltage (12 to 24VDC), an external power supply will be required. A common ground will be needed between an external supply and the EA800-ip Power Out Aux (-).


HX93BC -  Wiring Guide

Take notice of power from the Aux Out (-) and the Sensor Input (-), on the PDF these are marked as #5 and #2. You should have a voltage reading between 0.6 VDC and 3.0 VDC between these two points if your input is around 12V. The wiring is internal, but you will be checking between AUX(-) and Sensor Input(-) terminals.

HX93BC (with additional power supply) - Wiring Guide

HX71-MA-NB (not recommended for a cooler or condensing environment) - Wiring Guide

The HX71 only has 2 wires, so one is power the other is the sensor Input. Voltage is regulated by the sensor and grounded internally. Thus you will still be reading the voltage the same, between (-) Power Aux and (-) Sensor Input. Again, the reading should be between 0.6 and 3.0 VDC if your input is around 12V.

 Dwyer RH-R -  Wiring Guide


Application Model
Humidity inside a cooler

Omegea HX92BC, HX93BC, or HX94CW series

Differential Pressure Dwyer 605 & DH3
Fuel Detection Omega LV132 (switched output, not 4-20ma)
Combustible Gas Detection Detcon FP-524D
 Humidity inside a cooler (medical) Dwyer RH-R



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