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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Electricity meter | 1/9 | https://en.wikipedia.org/wiki/Electricity_meter | reference | science, encyclopedia | 2026-05-05T09:42:32.585250+00:00 | kb-cron |
An electricity meter, electric meter, electrical meter, energy meter, kilowatt-hour meter, or power meter is a device that measures the amount of electric energy consumed by a residence, a business, or an electrically powered device over a time interval. Electric utilities use electric meters installed at customers' premises for billing and monitoring purposes. They are typically calibrated in billing units, the most common one being the kilowatt hour (kWh). They are usually read once each billing period. When energy savings during certain periods are desired, some meters may measure demand, the maximum use of power in some interval. "Time of day" metering allows electric rates to be changed during a day, to record usage during peak high-cost periods and off-peak, lower-cost, periods. Also, in some areas meters have relays for demand response load shedding during peak load periods.
== History == The earliest commercial uses of electric energy, in the 1880s, had easily predictable usage; billing was based on the number of lamps or motors installed in a building. However, as usage spread, and especially with the invention of pluggable appliances, it also became more variable, and the electric utilities sought a means to bill customers based on actual rather than estimated usage.
=== Direct current ===
Many experimental types of meter were developed. Thomas Edison at first worked on a direct current (DC) electromechanical meter with a direct reading register, but instead developed an electrochemical metering system, which used an electrolytic cell to totalise current consumption. At periodic intervals the plates were removed and weighed, and the customer billed. The electrochemical meter was labor-intensive to read and not well received by customers. DC meters often measured charge in ampere hours. Since the voltage of the supply should remain substantially constant, the reading of the meter was proportional to actual energy consumed. For example, if a meter recorded that 100 ampere hours had been consumed on a 200-volt supply, then 20 kilowatt-hours of energy had been supplied. In 1885 Ferranti offered a mercury motor meter with a register similar to gas meters; this had the advantage that the consumer could easily read the meter and verify consumption. Another early electromagnetic meter with visible readouts was a DC meter by Hermann Aron, who patented it in 1884. Hugo Hirst of the British General Electric Company introduced it commercially into Great Britain from 1888. Aron's power meter (later adapted for AC power) recorded the total charge used over time, and showed it on a series of clock dials.
Electrochemical meters were also improved to be directly read out, such as the Bastian electrolytic meter invented in 1897, and the Wright electrolytic meter or 'Reason' meter which was patented in 1900. The Wright meter, used mainly in the United Kingdom, consisted of a vertically mounted glass structure with a mercury reservoir at the top of the meter. As current was drawn from the supply, electrochemical action transferred the mercury to the bottom of the column. The height of the mercury indicated the total charge. The meter had to be reset to zero before the reserve of mercury ran out. Reset was performed by inverting the meter, restoring the mercury to the reservoir.
=== Alternating current === The first specimen of the AC kilowatt-hour meter produced on the basis of Hungarian Ottó Bláthy's patent and named after him was presented by the Ganz Works at the Frankfurt Fair in the autumn of 1889, and the first induction kilowatt-hour meter was already marketed by the factory at the end of the same year. These were the first alternating-current watt-hour meters, known by the name of Bláthy-meters. The AC kilowatt hour meters used at present operate on the same principle as Bláthy's original invention. Also around 1889, Elihu Thomson of the American General Electric company developed a recording watt meter (watt-hour meter) based on an ironless commutator motor. This meter overcame the disadvantages of the electrochemical type and could operate on either alternating or direct current. In 1894 Oliver Shallenberger of the Westinghouse Electric Corporation applied the induction principle previously used only in AC ampere hour meters to produce a watt-hour meter of the modern electromechanical form, using an induction disk whose rotational speed was made proportional to the power in the circuit. The Bláthy meter was similar to Shallenberger and Thomson meter in that they are two-phase motor meter. Although the induction meter would only work on alternating current, it eliminated the delicate and troublesome commutator of the Thomson design. Shallenberger fell ill and was unable to refine his initial large and heavy design, although he did also develop a polyphase version. In 1902, William Morris Mordey and Guy Carey Fricker patented the Mordey-Fricker electricity meter, which operated on a different principle from motor-type meters, using a clock mechanism whose balance wheel oscillated at a rate directly proportional to the current. It was suitable for both direct and alternating current without frequency error, and was designed for small domestic installations of twelve to thirty lamps.
== Units ==