I have a very interesting little project that came up, and I was contemplating using a simplified Arduino system to accomplish what I need, but am not sure if I can make it work.
Basically, I have a Baumer inductive proximity sensor that is providing a 4-20mA realtime position signal to a control system. The problem is, when the sensor is replaced or maintenance is done, getting the sensor back in the correct "neutral" position is tedious, since the feedback for the system is about 100 yards away in an operator's station. What we would like to do is tap that 4-20 signal, and put a small box close to the sensor location that has just use a few basic LEDs to guide the maintenance crew when aligning the sensor. I am thinking a green LED that lights up when it's in the proper centered range (12mA +/- maybe 1mA), and a red LED on either side of the green to indicate if it's too far to the left or right. The Arduino code should be very easy, once I determine how to properly read a 4-20 analog signal.
But, my issue is the power and signal itself. The Baumer sensor is a 3 wire affair: +24V out, signal wire, common wire. I need to tap the signal to detect position, but not affect the signal upstream at the controller. But I also need to tap the power from that signal, if possible - if not, running separate 24V power to the unit is possible, but not ideal.
Any thoughts on how to come at this? The idea is to build something very basic, rather than forcing a move to expensive LED bar graph types of displays, which is one of our few alternatives at this point.