Definition of energy meter
The energy meter used to measure the power load is called the energy meter. Energy is the total power consumed and used by the load in a specific time interval. It is used to measure the power consumption of home and industrial AC circuits. Electricity meters are not so expensive or so accurate.
How Energy Meters Work
The electric energy meter has an aluminum plate, and the rotation of the aluminum plate determines the power consumption of the load. The disc is placed between the air gap of the series electromagnet and the parallel electromagnet. The parallel magnet has a pressure coil and the series magnet has a current coil.
The pressure coil produces a magnetic field due to the supply voltage and the current coil produces a magnetic field due to the current.
The magnetic field produced by the voltage coil lags 90 degrees behind that of the current coil because of eddy currents in the disk. The interaction of eddy current and magnetic field produces torque, which exerts force on the disk. As a result, the disc begins to rotate.
The force on the disk is proportional to the current and voltage of the coil. Permanent magnets control their rotation. The permanent magnet opposes the motion of the disk and makes its power consumption equal. The tachometer calculates the rotation of the disc.
Accuracy of energy meter
The energy meter must record the consumed energy within the acceptable accuracy range. Any significant error in the registration of energy could mean a loss to power suppliers, or consumers being overcharged. The accuracy is usually specified in the regulations for the instrument installation location. Legal provisions may also provide for procedures to be followed when there is a dispute over accuracy.
For the UK, any installed meter needs to accurately record the energy consumed, but it is allowed to read 3.5% lower or 2.5% higher. The disputed meter was initially verified by a check meter running next to the disputed meter. The final solution is to fully test the instruments in dispute in the installation location and professional calibration laboratory. About 93% of the instruments in dispute operate well. Only when the laboratory can estimate the time when the meter was wrongly recorded can the paid but unused electricity be returned (and vice versa). This is in contrast to the gas meter. If it is found that the reading of the gas meter is insufficient, it is assumed that as long as the user supplies gas through the gas meter, the reading of the gas meter will always be insufficient.