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Comment by lucaspiller | Hacker News Reader

You can also buy clamp sensors that can be connected directly to a microcontroller (with an ADC - so not a Raspberry Pi without external hardware).

http://www.homautomation.org/2013/09/17/current-monitoring-w...

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The clamp only systems lack accuracy due to not measuring supply voltage. Commercial/open source energy meters based on chips like the ADE7953[0] have a resistive voltage divider to attenuate the supply voltage to suitable level for the chip but preserving the envelope for sampling. The problem is there is no galvanic isolation, so interfacing is harder.

[0] http://www.analog.com/en/products/analog-to-digital-converte...

I have a similar set up with a Z-wave clamp style current meter[0]. This meter is calibrated to 120v. I use NUT to grab the line voltage off the UPS and adjust the reported current with actual voltage to get power. It's good enough for the girls I go out with

[0] https://www.amazon.com/Aeon-Labs-AEDSB09104ZWUS-Aeotec-Monit...

I have the same meter, that meter actually reports voltage to me though.

There are transformer isolated energy monitors like MAX78615. Much safer to work with.

Resistors are cheaper. Much better for the bottom line.

MAX78700 uses a pulse transformer for isolation from the MAX78615, and is powered by the '78615 via that same transformer. It uses resistors for voltage and current sensing.

If you got 3 phases going into your house, how would you use this sensor? Do you need 2, or even 3, of them?

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