1. Measurement technology

1.1 Measured values

However complex a metering system may be, the basic electrical quantities that can be measured are always voltage and current, provided that frequency is included in the reference values. These two basic quantities can be used to construct various other quantities:

• RMS voltage U (more or less averaged over a period of time to be defined) ;

• RMS intensity I (more or less averaged over a period of time to be defined) ;

• instantaneous or averaged active power P, which results in active energy ;

• instantaneous...