Wiring question on the 1-Channel 4-20mA Current Loop Receiver

Hi all,

I recently purchased the 1-Channel 4-20mA Current Loop Receiver (click) and had a quick question on how i’m supposed to wire this up to an existing 4-20ma loop to read sensor data.

The existing loop has a pt100 transmitter and a 20-420C 3-wire RTD. When I put a multimeter in series i get the expected 5.13ma at room temperature so i know the loop is working properly. To read the loop current with the current loop receiver i tried putting it in series after the pt100 but I am getting a very low current reading, 0.041. How should this be wired?

FYI, i’m using an Adafruit Feather Huzzah and following the tutorial here.



whats the operating voltage of the pt100 transmitter ?


I’m supplying 24v to the loop.

the board has on board supply. it wont need an external power supply.
You can directly connect the 4-20mA current loop vin and gnd to pt100.

OK. Maybe I purchased the wrong product. What should I use to read current in an existing loop?

This one

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This board has a external power input… i cant find the input voltage… might be 24v ?? (Industry standard)

The DC input voltage range is 6V to 32V.


Really disappointing this information (input power requirements) isn’t listed anywhere either in the sparse documents or on the board itself. I thought the board could be powered externally (if driving the loops) or via the I2C connection (if loops have their own power supply which is my use case). Now I’m going to have to add a DC/DC converter just to bring voltage up from 5V to 6V to run this thing - seems a waste.