Isolated AC line current sensors

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


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