Editing Dummy load

{{Short description|Device used to simulate an electrical load}}
{{more footnotes|date=February 2015}}

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| caption1 = Small RF dummy load with capacity of 1 kW at frequencies up to 450 MHz. It consists of a 50Ω resistor immersed in oil to absorb the heat.
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| caption2 = Large RF dummy load for [[shortwave]] transmitter at the Moosbrunn transmitting station of the Austrian Broadcasting Service, Moosbrunn, Austria. It uses a [[sodium hydroxide]] solution to absorb the radio energy, which is circulated through the radiator ''(center)'' to cool it. It has a capacity of 100 kW.
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A '''dummy load''' is a device used to simulate an [[electrical load]], usually for testing purposes. In [[radio]] a '''dummy antenna''' is connected to the output of a [[radio transmitter]] and electrically simulates an [[antenna (radio)|antenna]], to allow the transmitter to be adjusted and tested without radiating [[radio wave]]s. In [[audio system]]s, a dummy load is connected to the output of an amplifier to electrically simulate a [[loudspeaker]], allowing the amplifier to be tested without producing sound. [[Load bank]]s are connected to electrical [[power supply|power supplies]] to simulate the supply's intended [[electrical load]] for testing purposes.

==Radio==
[[File:Waveguide dummy load.jpg|thumb|Microwave dummy load designed to attach to [[waveguide]].]]

{{See also|Antenna (radio)|Standing wave ratio}}
In radio this device is also known as a '''dummy antenna''' or a '''[[radio frequency]] termination'''.  It is a device, usually a [[resistor]], used in place of an [[antenna (radio)|antenna]] to aid in testing a [[radio transmitter]]. It is substituted for the antenna while one adjusts the transmitter, so that no radio waves are radiated so that the transmitter does not [[Electromagnetic interference|interfere]] with other radio transmitters during the adjustments.
(As no dummy load is ideal, however, some radiation does occur).
<ref>{{cite book
|title=ARRL Handbook for the Radio Amateur
|year=1990
|publisher=American Radio Relay League
|location=Newington, Connecticut
|editor=Kleinschmidt, Kirk
|pages=25–21 through 25–23}}</ref>  If a transmitter is tested without a load attached to its output terminals such as an antenna or a dummy load, the power will be reflected back into the transmitter, often overheating and damaging it.   Also, if a transmitter is adjusted without a load, it will operate differently as compared with a load, and the adjustments may be incorrect.

The dummy load ordinarily should be a pure [[Electrical resistance|resistance]]; the amount of resistance should be the same as the [[Electrical impedance|impedance]] of the antenna or transmission line that is used with the transmitter (usually 50 Ω or 75 Ω).<ref>{{cite book
|title=ARRL Handbook for the Radio Amateur
|year=1990
|publisher=American Radio Relay League
|location=Newington, Connecticut
|editor=Kleinschmidt, Kirk
|pages=25–21
}}</ref>
The radio energy that is absorbed by the dummy load is converted to heat. A dummy load must be chosen or designed to tolerate the amount of power that can be delivered by the transmitter.<ref>{{cite book
|title=ARRL Handbook for the Radio Amateur
|year=1990
|publisher=American Radio Relay League
|location=Newington, Connecticut
|editor=Kleinschmidt, Kirk
|pages=34–22 through 34–28
}}</ref>  Typically it consists of a [[resistor]] attached to some type of [[heat sink]] to dissipate the power from the transmitter.

The ideal dummy load provides a standing wave ratio ([[Standing wave ratio|SWR]]) of 1:1 at the given [[Electrical impedance|impedance]].

Veterinarian-grade [[mineral oil]], an inexpensive form of mineral oil, is frequently used by [[amateur radio]] operators as coolant in RF dummy loads.

==Audio==
{{see also|Thiele/Small parameters|Electrical characteristics of dynamic loudspeakers}}
[[File:Resistor loads for amplifier test.jpg|thumb|upright|Four heavy duty dummy loads used at an amplifier shootout]]
When testing [[audio amplifier]]s, it is common to replace the [[loudspeaker]] with a dummy load, so that the amplifier's handling of large power levels can be tested without actually producing intense sound.  The simplest is a resistor bank to simulate the [[voice coil]]'s resistance.

For loudspeaker simulation, a more complex network is more accurate, however, as actual loudspeakers are [[Reaction (physics)|reactive]] and [[non-linear]].  There are many designs for loudspeaker simulators, which emphasize different characteristics of the actual speaker, such as the [[voice coil]]'s inductance, mechanical suspension compliance, and cone mass.

==Power supplies==
There are also dummy loads for power supplies, known as [[load bank]]s. These may be used, for example, for factory and in-service testing of standby generators.  A load bank may be used to stabilize a power system in case of loss of load, for example, on an isolated wind or mini-hydro plant.

An '''electronic load''' (or '''e-load''') is a device or assembly that simulates [[electrical load|loading]] on an electronic circuit.
It is used as substitute for a conventional ohmic load resistor.
[[Image:ZS Lasten 01 klein.JPG|thumb|Electronic loads with 800W and 4200W from Höcherl & Hackl]]

As counterpart to a [[current source]], the electronic load is a '''current sink'''. When loading a current source with a fixed resistor one can set one determined load current by the connected load resistor. The characteristic of the electronic load is that the load current can be set and varied in a defined range. The load current is regulated electronically.

The electronic load consumes [[electric energy]] and in most cases transforms it into [[heat]]. Fans or water-cooled elements are used as coolers. Under certain conditions, energy-recycling into the public power supply system is also possible.

Electronic loads are used in diverse applications, particularly for the test of [[power supply|power supplies]], [[electric battery|batteries]], [[solar cell|solar]] and [[fuel cell]]s, [[Electrical generator|generator]]s. AC loads are used to test [[transformer]]s, [[uninterruptible power supply|uninterruptible power supplies]] (UPS) or [[onboard power supply|onboard power supplies]].
The equipment and power spectrum of such electronic loads begins with simplest circuits consisting in general of a potentiometer for current setting and a transistor circuit for power transforming. Further developed electronic loads supply several operating modes, in most cases constant current, voltage, power and resistance. Nowadays, the equipment may be controlled by a [[Programmable logic controller|PLC]] or remotely by a PC. Settings and measured values such as input voltage and actual load current are indicated on a display.

==See also==
*[[Electrical termination]]
*[[Electrical impedance]]
*[[Resistor#Grid resistor|Grid resistor]]

==References==
<references />

==Further reading==
*{{cite news|title=Power MOSFET is core of regulated-dc electronic load|author1=Ausias Garrigós |author2=José M Blanes |date=2005-03-17|url=http://edn.com/design/power-management/4321777/Power-MOSFET-is-core-of-regulated-dc-electronic-load|publisher=EDN}}
*{{cite news|url=http://reed-electronics.com./tmworld/article/CA6291890.html#Loads%20need%20calibration,%20too|work=Ensuring power supply accuracy|title=Loads need calibration, too|author=Martin Rowe|date=2005-12-01|publisher=Test and Measurement World}}
*{{cite journal|title=Inductive electronic load for testing of magnet power supplies in particle accelerators|author1=M. B. Borage |author2=S. R. Tiwari |author3=S. Kotaiah |date=2003-07-07|journal=Review of Scientific Instruments|volume=74|issue=12|pages=5194&ndash;5196|doi=10.1063/1.1622971|bibcode=2003RScI...74.5194B }}
*{{cite book|chapter= Design and implementation of a real-time lossless dynamic electronic load simulator|author1=Meng-Yueh Chang |author2=Jiann-Yow Lin |author3=Shih-Liang Jung |author4=Ying-Yu Tzou |title= PESC97. Record 28th Annual IEEE Power Electronics Specialists Conference. Formerly Power Conditioning Specialists Conference 1970-71. Power Processing and Electronic Specialists Conference 1972|date=1997-06-27|volume=1|pages=734&ndash;739|isbn=0-7803-3840-5|doi=10.1109/PESC.1997.616801|s2cid=111355663 }}
*{{cite journal |doi=10.1049/ip-gtd:20040056|title=Analysis and implementation of an electronic load controller for a self-excited induction generator|journal=IEE Proceedings - Generation, Transmission and Distribution|volume=151|pages=51|year=2004|last1=Singh|first1=B.|last2=Murthy|first2=S.S.|last3=Gupta|first3=S.|doi-broken-date=7 December 2024 }}

==External links==
*[http://www.epanorama.net/documents/audio/speaker_impedance.html Speaker impedance] - ePanorama.net

{{Analogue TV transmitter topics}}

[[Category:Electrical circuits]]
[[Category:Radio electronics]]