1) Apparent or active
Does an current clamp measure apparent or active current?
I am looking at energy consumption metering solutions for a building. So far, the affordable products seem to click clamps on one or more of the phases (and maybe on zero) going into the house.
Or maybe some products measure one, and some measure the other?
2) Reliability / precision of clamps
Is a clamp on the outside of a cable really precise? Maybe only the high-end / expensive clamps are precise? Or is this such a simple principle that I can even trust relatively cheap solutions, such as Efergy (link to installation instruction video)?
Are non-clamp solutions generally more reliable/precise?
Best Answer
A clamp-on ammeter has no way of knowing the phase relationship between the current and the voltage, so it only gives a magnitude reading, which I guess is what you're calling "apparent current". It can't mesaure "real power" unless it also has a voltage reference input.
The split core of a good clamp-on meter gives readings that are as accurate as a non-split current transformer. In any case, read the accuracy specifications of the meter you're considering.