As of now, I have a fairly good understanding about the 4-20mA current loop standard.
It needs, of course, a sensor with either 2-wire or 3-wire output 4-20mA (4mA as zero reading and 20mA full-scale output).
A Power supply that must be sufficient for the input voltage of the sensor input and voltage drop across a 220Ohm Resistor.
Then lastly, since analog current passes through the resistor, the analog voltage drop can be obtained by a microcontroller via ADC.
But I noticed in my research that only one sensor is being used.
I want to use 2 different sensors with 4-20mA output. How do I start with this? Should I use two different loops for each sensor? Can I just use 2 different analog input channels?
Thank you.
Best Answer
The best way to understand this is to look at wiring diagrams from actual vendors.
For instance, Acromag has such a diagram, if you look here p7/8 you will see that your 2 loop transmitter can share the same 24VDC power supply but need 2 different input channels.
I have extracted here for illustration and in case the link goes dead later: