I have a current loop (pls see attached). The loop runs a distance of about 500 meters. There's 20mA on the wire supplied by a current source at the sender off of an LM317 regulator. At the receiver I want to measure the current value on the loop wire. I put a 50ohm Rsense resistor at the receiver so I can read 1V when there is 20mA on loop. However this Rsense is floating (not ground referenced) because I need ground reference further down in wire (attached picture might make this clearer). So my question is: sinse Rsense is floating, how do I measure the voltage difference across it?
(I think an opamp comparator across the Rsense might do but I would have to single supply the opamp with one of the Vin's equal to Vs+. I think this makes getting Vout to = 1V (or less when there is < 20mA on the current loop) hard.)
Is there a good method to measure voltage across Rsense? Or can I use a different approach, everything can be substituted.
(I think an opamp comparator across the Rsense might do but I would have to single supply the opamp with one of the Vin's equal to Vs+. I think this makes getting Vout to = 1V (or less when there is < 20mA on the current loop) hard.)
Is there a good method to measure voltage across Rsense? Or can I use a different approach, everything can be substituted.
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