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I'm working on a project where I have to implement a metering IC to measure Voltage, Current and Power on 230v power lines.

I have to use Atmel's 90E24 single phase metering IC. This IC has two channels one for Phase and another for Neutral current metering.

Since, all the current drawn by the load will flow on both phase and neutral (return path) then what is the significance of using two line metering?

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up vote 4 down vote accepted

You would typically monitor the neutral as part of an anti-tampering technique. People might bypass only the line , in which case the return current through the neutral would be different (higher) than what is on the Line. If both the L and N were by-passed then the neutral voltage might change (depending upon when the ground connection is made).

On Edit: looking at the datasheet it says " In anti-tampering mode, the power difference threshold between L line and N line can be: 1%, 2%,... 12%, 12.5%, 6.25%, 3.125% ..." on page 13.

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