STPM32 power metering on LINE instead of NEUTRAL?

[leddel32]

Hi,

We are currently looking for a power metering IC. We are thinking of using the STPM32 for this purpose.

In our device we can only switch on and off the line to our load. The Neutral of the load is not passing through our device. It is connected to our same neutral though. So the only place we could place a current shunt is on the LINE and not in the NEUTRAL as in the evaluations schematics. 

Our STPM32 will have fully isolated power and communication lines.

- So we are now mandatory to use a current transformer or rogowsky coil?

- Are there any other ways of still measuring with a current shunt in line? 

- Because the circuit is fully isolated and there is no way to touch the circuit could we also refer to the LINE voltage instead of NEUTRAL?

Best regards

[AScha.3]

Hi,

just imagine : you are the power metering IC . 

You have a line, to check the current, and another to check the total voltage.

Which one is "hot" is not important - you even dont know it at all.

So...its same (as long as its fully isolated) : its sitting on line or neutral and checks the current here and the voltage from the "other" line, same result.

btw

I made a power meter using just an old F103 (on a blue pill board), can show down to 1 mW the power on the load;

because that interested me , not the usual 1...2000W range. No special power-metering-chip used.

And it can measure and show also the DC value on the mains and peaks up to 100A , what can happen, when connecting something to the mains.