Debugging 4-20ma MCP3428 non-isolated board

I received my new 4-channel board today and have been able to interface with the MCP3428 via my Particle Electron. So far as I can tell, everything is functional between the MCP3428 and the Electron. I have the board powered by an external battery running at 12v.

In order to test my new board, I got my4-20 pressure transducer out and put it on channel 1. When I try to read any of the channels, I keep getting lower numbers than I should for a sensor being connected (112 at 16-bit and 7 at 12-bit). In fact… the numbers don’t change at all when the sensor is connected or not.

I got out my voltmeter and there is no voltage on the screw down terminals for the sensor wires. Is something wrong with the board or am I missing something about how the 4-20ma is supposed to work?

Do you have the sensor power supply connected ? looks like your setup is missing the loop supply.


Do the barrel jack / screw terminals not power the sensors? I was under the impression that the board powered the device and supplied the voltage to the sensors as well.

No, it does not supply the power to the sensor.
this one provides the power

Doh… Ok. I supplied it with an external voltage and I’m getting a responsive reading. I suppose I missed that in the spec sheet before I made my purchase.

@jschmidt I am experiencing the same problems as you. Could you share with me how your wiring has finally been?