Dummy load


Dummy load
Cantenna dummy load suitable up to 30 MHz and up to 1 kW

A dummy load is a device used to simulate an electrical load, usually for testing purposes.

Contents

Radio

In radio this device is also known as a dummy antenna or a radio frequency termination. It is a device used in place of an antenna to aid in testing a radio transmitter. It is substituted for the antenna while adjusting the transmitter, so that the transmitter does not interfere with other radio transmitters during the adjustments. [1] If a transmitter is tested without a load, such as an antenna or a dummy load, the transmitter could be damaged. Also, if a transmitter is adjusted without a load, it will operate differently than with the load, and the adjustments may be incorrect.

The dummy load ordinarily should be a pure resistance; the amount of resistance should be the same as the impedance of the antenna or transmission line that is used with the transmitter (usually 50 Ω or 75 Ω).[2] 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. [3]

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

Veterinarian-grade mineral oil, an inexpensive source for mineral oil, is frequently used by amateur radio operators as coolant in RF dummy loads.

Audio

Four heavy duty dummy loads used at an amplifier shootout

When testing audio amplifiers, 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 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 banks.

An electronic load (or e-load) is a device or assembly that simulates loading on an electronic circuit. It is used as substitute for a conventional ohmic load resistor.

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 supplies, batteries, solar and fuel cells, generators. AC loads are used to test transformers, uninterruptible power supplies (UPS) or 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 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

References

  1. ^ Kleinschmidt, Kirk, ed (1990). ARRL Handbook for the Radio Amateur. Newington, Connecticut: American Radio Relay League. pp. 25–21 through 25–23. 
  2. ^ Kleinschmidt, Kirk, ed (1990). ARRL Handbook for the Radio Amateur. Newington, Connecticut: American Radio Relay League. pp. 25–21. 
  3. ^ Kleinschmidt, Kirk, ed (1990). ARRL Handbook for the Radio Amateur. Newington, Connecticut: American Radio Relay League. pp. 34–22 through 34–28. 

Further reading

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Dummy-Load — Der Ausdruck Ersatzlast (auch Ballast, engl. Dummy Load ) bezeichnet eine künstliche Last in der Elektronik und in der Hochfrequenztechnik, welche ersatzweise für Testzwecke zur Simulation der elektrischen Eigenschaften einer realen Baugruppe,… …   Deutsch Wikipedia

  • Dummy Load — Der Ausdruck Ersatzlast (auch Ballast, engl. Dummy Load ) bezeichnet eine künstliche Last in der Elektronik und in der Hochfrequenztechnik, welche ersatzweise für Testzwecke zur Simulation der elektrischen Eigenschaften einer realen Baugruppe,… …   Deutsch Wikipedia

  • Dummy — may refer to: Military dummy: dummy round a cartridge that is inert, i.e. contains neither primer nor gunpowder decoy fake military equipment intended to deceive the enemy Crash test dummy, a full scale replica of a human being, weighted and… …   Wikipedia

  • Load bank — A load bank is a device which develops an electrical load, applies the load to an electrical power source and converts or dissipates the resultant power output of the source. The purpose of a load bank is to accurately mimic the operational or… …   Wikipedia

  • dummy run — i. Any simulated firing pass in which the weapon is not released both in air to ground and air to air firing. ii. A trial approach to land, to pick up a load, or to release a load …   Aviation dictionary

  • Electrical load — If an electric circuit has a well defined output terminal, the circuit connected to this terminal (or its input impedance) is the load. (The term load may also refer to the power consumed by a circuit; that topic is not discussed here.)Load… …   Wikipedia

  • Unit dummy force method — The Unit dummy force method provides a convenient means for computing displacements in structural systems. It is applicable for both linear and non linear material behaviours as well as for systems subject to environmental effects, and hence more …   Wikipedia

  • Demand load — In telecommunication, the term demand load can have the following meanings: In general, the total power required by a facility. The demand load is the sum of the operational load (including any tactical load) and nonoperational demand loads. It… …   Wikipedia

  • Guitar effects — are electronic devices that modify the tone, pitch, or sound of an electric guitar, or condition or reroute the signal in some fashion. Effects can be housed in small effects pedals ( stomp boxes ), guitar amplifiers, guitar amplifier simulation… …   Wikipedia

  • Ersatzlast — Der Ausdruck Ersatzlast (auch Ballast, engl. dummy load ) bezeichnet eine künstliche Last in der Elektronik und in der Hochfrequenztechnik, welche ersatzweise für Testzwecke zur Simulation der elektrischen Eigenschaften einer realen Baugruppe,… …   Deutsch Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.