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Jman
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Using an Optocoupler to separate a 4-20mA loop

I have a PLC that is powered with 3.3V and a sensor powered with 12V that outputs a 4-20mA signal. In order to allow the signal to be readable by my PLC while isolating the current in the 12V loop from the 3.3V loop I need to use an optoisolator which I have never used before. I am hoping for some help figuring out the appropriate circuit.

The isolator I am looking at is the hcnr201 datasheet here

In the datasheet it gives a bunch of rather confusing wiring diagram examples that are not clear about where the optocoupler is in the diagram. I am wondering how I could hook it up in reality so that the circuit connected to my PLC is producing the same current as is going through the LED on the 12V side. My thinking is that the LED would be driven by my 4-20mA 12V loop (pins 1&2) and pins 5 & 6 I would connect to a 3.3V source that runs through the optocoupler and is then connected to a resistor with an ADC measuring the voltage drop across as seen in my diagram below:

OptoIsolatorInternals

enter image description here

Does my thinking make sense? It seems overly simple compared to the example circuits I was looking at in the datasheet. Thanks!

Jman
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