Re: Isolated AC line current sensors

At 08:04 PM 2025-07-21, you wrote:
>I've been asked about sensing current on the AC line. Current transformers
>immediately come to mind. Also, I see there are Hall effect based sensors
>(similar to current transformers, but using a Hall effect device instead
>of a secondary winding). For isolation, I also see linear optocouplers,
>that have two photosensors so the LED current can be servoed. Another
>method would be a current sense resistor with an isolation amplifier.
>
>I remember years ago an LTC RMS to DC converter that measured the
>temperature of a heater. It SEEMS like there could be a chip equivalent of
>a thermocouple ammeter with an electrically isolated heater and a
>temperature sensor.
>
>Other ideas?
>
>Thanks!
>
>Harold

There's always the good old (air core) Rogowski coil. It actually 
measures di/dt but
it's possible to work with that with AC mains current.

https://en.wikipedia.org/wiki/Rogowski_coil

Thermal is more useful for RF measurements, from what I have seen.

There are some chips that you mount overtop of a current-carrying trace, and
they use some magnetic properties (eg. tunneling magneto resistance) to measure
the current while being galvanically isolated. That works for DC or AC.

Best regards,
Spehro Pefhany