At times, it is useful to test a 4-20mA device in isolation before connecting it to a PLC or Gateway. The following method requires a 200ohm resistor and a multi-meter to read voltage:
Self powered devices
One easy way to verify if a 4-20mA device is working is put a 50 or 200 ohm resistor across the 4-20mA output and measure the voltage.
If the corresponding current is not within range, then the output is not working.
- 50 ohm → 0.2V - 1V
- 200 ohm → 0.8V - 4V
Externally powered devices
Some sensors require power, so then you might need to add power:
