Isolating a 4-20ma signal

M

Thread Starter

martcon

Hi,

I am trying to isolate a 4-20ma signal coming from a UV lamp unit on a water supply to a logger. I have a 100R resistor across this 4-20 on logger side at the moment to convert for the logger input, but due to a malfunction on the UV unit which allowed 110 V ac to pass on UV 4-20 I want to install an isolator.

The UV 4-20 MA output only has a small DC voltage across it (13vdc) so I am assuming it is not loop powered and would require an isolator with a separate 24 vdc power supply, does this sound correct?

Thanks in advance.
 
The loop powered isolators I'm familiar with scavenge power from the loop power supply (on the input side) to drive their own electronics and the loop current on the output side.

If it were me, and I had a loop powered isolator lying around, I'd try it. force the source to max at 20mA and see what happens, and since your load is only 100 ohms, it might work. Or it might fizzle, with the isolator unable to drive both loops at 20mA with the power available to it from the active output.

But if I didn't have one to try, I'd start out with a DC powered isolator and be done with it.
 
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