Comprehensive Guide to Learning PLCs
Configuring, scaling, and programming 4-20mA inputs and outputs.
So far you have used discrete or digital or binary signals that can either be ON/OFF or a 1/0. Many control systems will have analog inputs and outputs to measure processes, make more complex decisions, and do finer output control.
The PLC Tools SIM-ALP2 used in this video will be very helpful for both learning and testing sensors in the field. https://controls.tw/c-sim-alp2
In the Analog section, the "2 Wire Current Loop vs 4 Wire Current Source" will be important to understanding how to wire a 4-20mA sensor.