Isolated VDC measure

Hello people,

i am making an Inverter VFD 3phase project and i stucked on some sensors.

-For phase current (A,B,C) i will use LTS-6NP with fast responce,5V supply and also offers isolation.

  • I want to monitor VDC for overvoltage or undervoltage. (here is my questions)

I am thinking of using some isolated amplifier (like ACPL-790x) but most IC's needs an extra amplifier.

Do i realy need to add extra amplifier or its no need since i measure an DC voltage ;

Can i let Vout- unused an just use Vout+ to my Arduino's A/D ?

I work primarily on industrial electronics, including servo amps and VFDs, and if there’s anything I’ve learned it’s that isolation is always a good idea.

When everything works exactly as intended, nothing bad happens… when things fail, and you don’t have isolation, kiss every part of your drive goodbye.


Sorry, I didn’t see the remainder of your question.

The LEM’s output of 0-5V is already isolated, so it could be left as-is, but if you want extra isolation on the signal (and you should have it, even if you don’t want it) simply wiring an op-amp as a voltage follower will do. If you’re using an isolated op-amp, then ignoring the Vout- is fine, since it will simply be the differential. Ideally, you wouldn’t use an opamp with a differential output, though, since it’s added cost that isn’t necessary.

That said, since that part of the circuit is already isolated, the isolated opamp and the resulting multitude of power supplies needed would be gilding the lily.