Mechanical Energy Meters

Mechanical energy meters are discussed in high school physics books as applications of Lenz's law, viz., the generation of eddy currents which oppose the change that caused it. The number of revolutions of a metal disc between the poles of an electromagnet represents the amount of energy consumed. They are more accurately described as electro-mechanical meters, as they use mechanical components like a spinning disc to measure the energy consumed.

Electronic Energy Meters

Electronic meters work by measuring the current flowing through the resistors in it at any time. The unit of measurement in the meter is the number of pulses, which is the smallest unit of energy measured by the meter. The pulses are calibrated in terms of kilowatt-hours of electricity, typically 3200 pulses per unit. Apart from the numbered wheel display found in mechanical meters, the energy consumed is also noted inside chips in the meter, so tampering can be detected.