Multiple 4-20mA loops

Other Hardware Sensors
1

Hi All,

I'm having a problem introducing two 4-20mA loops onto an Uno - can anyone help?

I have a 24V DC Transformer with the + connected to the + of the pressure sensor, the - of the pressure sensor connected to a 250 Ohm resistor and then the - of the transformer connected to the other side of the resistor. The arduino A1 is connected to the + side of the resistor and the arduino GND to the - side of the resistor. On it's own, this circuit works fine and gives me good readings between 1V and 5V.

My problem is when I introduce an identical circuit for another pressure sensor and connect to the same transformer, A5 and the same ground. The Arduino simply freezes, ...

I have read about ground loops, floating grounds etc but am quite lost. Any help greatly appreciated.

Kind regards, Andrew

2

Need a circuit diagram . If the analog input is connected to the top of the resistor and the negative ends connected to both 0v and the 24v supply then it should be ok.