Types of electric meters and how they work

April 01, 2020

When you consider how difficult it must be to measure something which you cannot see, cannot taste, cannot grasp, cannot smell and cannot hear, you will realize how great of an accomplishment it was for engineers, like Oliver Shallenberger at Westinghouse, to invent the watt-hour electric meter.

There are more types of meters, detectors, and measurement devices than could possibly be listed here, but we will list a few of the most prominent which have really changed our world.

Watt-hour Meter

This is one of the most important meters ever invented. It measures the amount of AC current used in a set period of time. With an accurate way to measure power, devised in 1888, the electrical grid became more economical, and in the 1890s, the electrical industry flourished. On the business side of things, it was necessary to measure use in order to charge customers fairly. The traditional watt-hour meter used a disk that spins due to electromagnetic fields created by the current flow on specifically placed coils. A counter measured the number of rotations. The more energy one uses, the faster the disk spins.

The basic induction watt-hour meter while a bit more complex could be similar to a small electric motor running at a speed proportional to the amount of electrical power passing through it. It actually has two sets of coils one for potential flux interaction and one for current flux interaction with the meter disc or rotor. The motor rotates the disc inside the meter which drives a series of gears that move dials on a register. These dials are what meter readers look at every month to determine the amount of electricity consumed that month.


Measures voltage (electrical potential) across a circuit. Voltmeters measure the voltage difference between two places, such as two points within a circuit. The typical voltmeter has two terminals, connected to wires or "leads." Place the tip of one lead at one of the points to be tested and the tip of the other at the other point and the meter shows you the difference.


This meter is extremely useful, as it can show you the waveform of the signal (voltage or current) in a circuit you are working with. You can take a repetitive signal and display as a static line graphed on a screen, this can allow a human to see a pattern that was previously unobservable due to its passing at high speed.

Solid State Meters

Since the late 1970's electronic technologies tried to replicate the principle of induction metering without the electromagnetic components, that is without the disc and gears and dials. They are built in basically four major components: Sensors, Multipliers, Numerical Converter and Registers.

Sensors provide the means of bringing a proportional Voltage and proportional current to the metering circuit (today a micro-component). The Multipliers are the processor where the values of Voltage and Current are multiplied to obtain the value of power, and the numerical converter is where these numbers are translated into a readable form that can be processed by the registers. The registers at the last stage take the translated numbers and display them or transmit them in the units that are usable for measurement.

Now this is an oversimplified view of a modern electronic meter, we are missing plenty other components like multiplexers, analog to digital converters, Microprocessors, internal clocks, super capacitors, displays, communication boards, input and output boards.

Today electronic metering technology uses Digital Signal Sampling of the analogue values of voltage and current and transforms them into a series of digital values, or a series of samples. The more samples in a specific period of time the more accurate the reading. This technology has allowed meters to provide more valuable data to the user than ever before; while an electromagnetic meter provided real energy (KWH), meters today provide voltage, current, power factor, real power and energy, apparent power and energy, reactive power and energy, harmonic distortion and in some cases wave and event capturing.

Smart Energy Meters

It is an advanced metering technology involving placing intelligent meters to read, process, and return valuable data to the providers and the customers. It measures energy consumption in real time, allowing for the participation in Demand Response programs to make the grid more stable. The accumulation of data points from multiple points and multiple customers provide also the ability to refine predictive algorithms on future electricity consumption, that make a unidirectional grid, smarter. Smart metering systems use advanced metering infrastructure system technology for better performance.

Another benefit of electronic technology is the reduction in size and cost, opening the door for submetering to provide similar benefits to building, owners, and energy managers.

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