Archived Forum

See here: http://openenergymonitor.org/emon/buildingblocks/ct-and-ac-power-adaptor...

This is AC, polarity shouldn't really matrer

"This is AC, polarity shouldn't really matrer"

You are wrong:

Ac sensor polarity, together with the CT polarity / orientation, defines which sign - positive or negative - power flow represents imported power or exported power. Many users on this site generate power so knowledge of the direction of power flow is important to them.

As Robert has said, it does matter because if you connect them the wrong way round, emon will not function correctly.

Easy way to tell; connect up emon and check the readings. If they are negative in value, ie. -128, then swop round the low voltage AC connections so that emon reads a positive value. (assuming that you are measuring power usage).

Paul

Actually, Paul, he could be half right: I had forgotten that there is a current-only demo sketch that assumes the system voltage, so it does not know about phase, vars, real power, power factor or import/export. And only guesstimates VA and calls it power. (Just like the Efergy and some others). So if he was thinking about polarity or orientation of the CT, then in that particular case it doesn't matter.

I wrote the "standard" in the Installation and Calibration notes so that there would be a reference and people who followed that would get consistent and meaningful results.

I stand corrected and ashamed