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درباره:
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An electricity meter, electric meter, electrical meter,
<a href="http://www.jianxintechnical.com/energy-meter/"
target="_self">energy meter</a>, or kilowatt-hour meter is a
device that measures the amount of electric energy consumed
by a residence, a business, or an electrically powered
device. Electric meter or energy meter measures the total
power consumed 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.
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(1) Electric energy meters can be divided into DC
electric energy meters and AC electric energy meters
according to the circuits they use. AC electric energy meters
can be divided into <a
href="http://www.jianxintechnical.com/energy-meter/single-
phase-energy-meter/" target="_self">single phase energy
meter</a>s, three-phase three-wire electric energy meters and
three-phase four-wire electric energy meters according to
their phase lines; (2) Electric energy meters can be divided
into electrical-mechanical electric energy meters and
electronic electric energy meters (also known as static
electric energy meters, solid-state electric energy meters)
according to their working principles. Electromechanical
electric energy meters are used in AC circuits as ordinary
electric energy measuring instruments, and the most commonly
used ones are inductive electric energy meters. Electronic
energy meters can be divided into fully electronic energy
meters and electromechanical energy meters; (3) Electric
energy meters can be divided into integral electric energy
meters and split electric energy meters according to their
structure; (4) Electric energy meters can be divided into
active electric energy meters, reactive electric energy
meters, maximum demand meters, standard electric energy
meters, multi-rate time-of-use electric energy meters,
prepaid electric energy meters, loss electric energy meters
and multi-functional electric energy meters according to
their uses; (5) Electric energy meters can be divided into
ordinary installed electric energy meters (0.2, 0.5, 1.0,
2.0, 3.0 grades) and portable precision electric energy
meters (0.01, 0.02, 0.05, 0.1, 0.2 grades) according to their
accuracy levels.
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A <a href="http://www.jianxintechnical.com/energy-meter-
parts/relay/" target="_self">relay</a> is an electrically
operated switch. It consists of a set of input terminals for
a single or multiple control signals, and a set of operating
contact terminals. The switch may have any number of contacts
in multiple contact forms, such as make contacts, break
contacts, or combinations thereof. Relays are used where it
is necessary to control a circuit by an independent low-power
signal, or where several circuits must be controlled by one
signal. Relays were first used in long-distance telegraph
circuits as signal repeaters: they refresh the signal coming
in from one circuit by transmitting it on another circuit.
Relays were used extensively in telephone exchanges and early
computers to perform logical operations. The traditional form
of a relay uses an electromagnet to close or open the
contacts, but other operating principles have been invented,
such as in solid-state relays which use semiconductor
properties for control without relying on moving parts.
Relays with calibrated operating characteristics and
sometimes multiple operating coils are used to protect
electrical circuits from overload or faults; in modern
electric power systems these functions are performed by
digital instruments still called protective relays. Latching
relays require only a single pulse of control power to
operate the switch persistently. Another pulse applied to a
second set of control terminals, or a pulse with opposite
polarity, resets the switch, while repeated pulses of the
same kind have no effects. Magnetic Latching relays are
useful in applications when interrupted power should not
affect the circuits that the relay is controlling.
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