AMMETER

ammeter

An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. Early ammeters were laboratory instruments which relied on the Earth's magnetic field for operation. By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems.

The relation between electric current, magnetic fields and physical forces was first noted by Hans Christian rsted who, in 1820, observed a compass needle was deflected from pointing North when a current flowed in an adjacent wire. The tangent galvanometer was used to measure currents using this effect, where the restoring force returning the pointer to the zero position was provided by the Earth's magnetic field. This made these instruments usable only when aligned with the Earth's field. Sensitivity of the instrument was increased by using additional turns of wire to multiply the effect the instruments were called "multipliers.GeneratorA motorgenerator (an MG set or a dynamotor for dynamomotor) is a device for converting electrical power to another form. Motorgenerator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line. Large motorgenerators were widely used to convert industrial amounts of power while smaller motorgenerators (such as the one shown in the picture) were used to convert battery power to higher DC voltages.

Low-powered devices such as vacuum tube mobile radio receivers did not use motorgenerators. Instead, they would typically use an inverter circuit consisting of a vibrator (a self-exciting relay) and a transformer to produce the B+ voltages required for the vacuum tubes.

While a motorgenerator set may consist of distinct motor and generator machines coupled together, a single unit motorgenerator will have both rotor coils of the motor and the generator wound around a single rotor, and both coils share the same outer field coils or magnets. Typically the motor coils are driven from a commutator on one end of the shaft, when the generator coils output to another commutator on the other end of the shaft. The entire rotor and shaft assembly is smaller in size than a pair of machines, and may not have any exposed drive shafts.

Galvanometer

D'Arsonval/Weston galvanometer movement - with the moving coil shown in orange.

A galvanometer is a type of sensitive ammeter: an instrument for detecting electric current. It is an analog electromechanical actuator that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field.

Galvanometers were the first instruments used to detect and measure electric currents. Sensitive galvanometers were used to detect signals from long submarine cables, and to discover the electrical activity of the heart and brain. Some galvanometers use a solid pointer on a scale to show measurements, other very sensitive types use a miniature mirror and a beam of light to provide mechanical amplification of low level signals. Initially a laboratory instrument relying on the Earth's own magnetic field to provide restoring force for the pointer, galvanometers were developed into compact, rugged, sensitive portable instruments essential to the development of electrotechnology. A type of galvanometer that records measurements permanently is the chart recorder. The term has expanded to include use of the same mechanism in recording, positioning, and servomechanism equipment.

Camera

A rangefinder cameraA camera is an optical instrument that records images that can be stored directly, transmitted to another location, or both. These images may be still photographs or moving images such as videos or movies. The term camera comes from the word camera obscura (Latin for "dark chamber"), an early mechanism for projecting images. The modern camera evolved from the camera obscura. The functioning of the camera is very similar to the functioning of the human eye.A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum[1] A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium. A shutter mechanism controls the length of time that light can enter the camera.[2] Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.[3] A data display, often a liquid crystal display (LCD), permits the user to view settings such as film speed, exposure, and shutter speed.A film or video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved

Radio

Radio is the radiation (wireless transmission) of electromagnetic signals through the atmosphere or free space.[n 1] Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

Radio systems need a transmitter to modulate (change) some property of the energy produced to impress a signal on it. Some types of modulation include amplitude modulation and frequency modulation. Radio systems also need an antenna to convert electric currents into radio waves, and vice versa. An antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected. The electromagnetic wave is intercepted by a tuned receiving antenna. A radio receiver receives its input from an antenna and converts it into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc.[2] Radio frequencies occupy the range from a 3kHz to 300GHz, although commercially important uses of radio use only a small part of this spectrum

Steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.

Using boiling water to produce mechanical motion goes back over 2000 years, but early devices were not practical. The Spanish inventor Jernimo de Ayanz y Beaumont patented in 1606 the first steam engine. In 1698 Thomas Savery patented a steam pump that used steam in direct contact with the water being pumped. Savery's steam pump used condensing steam to create a vacuum and draw water into a chamber, and then applied pressurized steam to further pump the water. The first commercial true steam engine using a piston was developed by Thomas Newcomen and was used in 1712 for pumping in a mine. See: Newcomen atmospheric engineIn 1781 James Watt patented a steam engine that produced continuous rotative motion.[1] Watt's ten-horsepower engines enabled a wide range of manufacturing machinery to be powered. The engines could be sited anywhere that water and coal or wood fuel could be obtained. By 1883, engines that could provide 10,000hp had become feasible.[2] Steam engines could also be applied to vehicles such as traction engines and the railway locomotives. The stationary steam engine was a key component of the Industrial Revolution, allowing factories to locate where water power was unavailable.

Thermometer

Mercury thermometer for measurement of room temperature.

A thermometer is a device that measures temperature or a temperature gradient using a variety of different principles.[1] A thermometer has two important elements: the temperature sensor (e.g. the bulb on a mercury-in-glass thermometer) in which some physical change occurs with temperature, plus some means of converting this physical change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer).Operating principles of thermometers include the thermal expansion of solids or liquids with temperature, or the change in pressure of a gas on heating or cooling. Radiation-type thermometers measure the infrared energy emitted by an object, allowing measurement of temperature without contact.Thermometers are widely used in industry to control and regulate processes, in the study of weather, in medicine, and scientific research.

Some of the principles of the thermometer were known to Greek philosophers of two thousand years ago; by the 18th century, standardized scales allowed the readings of different thermometers inter-comparable.

Transformer

Pole-mounted distribution transformer with center-tapped secondary winding used to provide 'split-phase' power for residential and light commercial service, which in North America is typically rated 120/240V.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Transformer" \l "cite_note-Mack_.282006.29-2" [2]A transformer is an electrical device that transfers energy between two or more circuits through electromagnetic induction.

Avarying current in the transformer's primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varying electromotive force (emf) or voltage in the secondary winding. Making use of Faraday's Law in conjunction with high magnetic permeability core properties, transformers can thus be designed to efficiently change AC voltages from one voltage level to another within power networks.

Transformers range in size from RF transformers less than a cubic centimetre in volume to units interconnecting the power grid weighing hundreds of tons. Awide range of transformer designs is encountered in electronic and electric power applications. Since the invention in 1885 of the first constant potential transformer, transformers have become essential for the AC transmission, distribution, and utilization of electrical energy.

Computer

Computer

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A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.

Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.

In World War II, mechanical analog computers were used for specialized military applications. During this time the first electronic digital computers were developed. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs)

Gramophone

A gramophone record (phonograph record in American English) or vinyl record, commonly known as "arecord", is an analog sound storage medium in the form of a flat polyvinyl chloride (previously shellac) disc with an inscribed, modulated spiral groove. The groove usually starts near the periphery and ends near the center of the disc. Phonograph records are generally described by their diameter in inches (12", 10", 7"), the rotational speed in rpm at which they are played (3313, 45, 78), and their time capacity resulting from a combination of those parameters (LP long playing, SP single, EP 12" single or extended play); their reproductive quality or "fidelity" ("high fidelity", "orthophonic", "full-range", etc.), and the number of audio channels provided ("mono", "stereo", "quad", etc.).

The Phonograph disc record was the primary medium used for music reproduction until late in the 20th century, replacing the phonograph cylinder record, with which it had co-existed, by the 1920s. By the late 1980s, digital media, in the form of the Compact Disc, had gained a larger market share, and the vinyl record left the mainstream in 1991.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Gramophone_record" \l "cite_note-2" [2] They continue to be manufactured and sold in the 21st century. In 2009, 3.5 million units shipped in the United States, including 3.2 million albums, the highest number since 1998,[3] and the format retains a niche market. They are especially used by DJs and many audiophiles for numerous types of music.

loudspeakerA loudspeaker (or loud-speaker or speaker) is an electroacoustic transducer;[1] a device which converts an electrical audio signal into a corresponding sound.[2] The first crude loudspeakers were invented during the development of telephone systems in the late 1800s, but electronic amplification by vacuum tube beginning around 1912 made loudspeakers truly practical. By the 1920s they were used in radios, phonographs, public address systems and theatre sound systems for talking motion pictures.

The most popular speaker used today is the dynamic speaker, invented in 1925 by Edward W. Kellogg and Chester W. Rice. The dynamic speaker operates on the same basic principle as a dynamic microphone, but in reverse, to produce sound from an electrical signal. When an alternating current electrical audio signal input is applied through the voice coil, a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's law of induction, which causes a paper cone attached to the coil to move back and forth, pushing on the air to create sound waves. Besides this most common method, there are several alternative technologies that can be used to convert an electrical signal into sound.

microscope

A microscope (from the AncientGreek: , mikrs, "small" and , skopen, "to look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.

There are many types of microscopes. The most common (and the first to be invented) is the optical microscope, which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electron microscope and the scanning electron microscope), the ultramicroscope, and the various types of scanning probe microscope.

On October 8, 2014, the Nobel Prize in Chemistry was awarded to Eric Betzig, William Moerner and Stefan Hell for "the development of super-resolved fluorescence microscopy," which brings "optical microscopy into the nanodimension".

microphone

A microphone, colloquially mic or mike (/

HYPERLINK "http://en.wikipedia.org/wiki/Help:IPA_for_English" \l "Key" \o "Help:IPA for English" m

HYPERLINK "http://en.wikipedia.org/wiki/Help:IPA_for_English" \l "Key" \o "Help:IPA for English" a

HYPERLINK "http://en.wikipedia.org/wiki/Help:IPA_for_English" \l "Key" \o "Help:IPA for English" k/),[1] is an acoustic-to-electric transducer or sensor that converts sound in air into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, two-way radios, megaphones, radio and television broadcasting, and in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors.

Most microphones today use electromagnetic induction (dynamic microphones), capacitance change (condenser microphones) or piezoelectricity (piezoelectric microphones) to produce an electrical signal from air pressure variations. Microphones typically need to be connected to a preamplifier before the signal can be amplified with an audio power amplifier or recorded.

petrol engine

A petrol engine (known as a gasoline engine in North America) is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels. It was invented in 1876 in Germany by German inventor Nicolaus August Otto. The first petrol combustion engine (one cylinder, 121.6 cm3 displacement) was prototyped in 1882 in Italy by Enrico Bernardi. In most petrol engines, the fuel and air are usually pre-mixed before compression (although some modern petrol engines now use cylinder-direct petrol injection). The pre-mixing was formerly done in a carburetor, but now it is done by electronically controlled fuel injection, except in small engines where the cost/complication of electronics does not justify the added engine efficiency. The process differs from a diesel engine in the method of mixing the fuel and air, and in using spark plugs to initiate the combustion process. In a diesel engine, only air is compressed (and therefore heated), and the fuel is injected into very hot air at the end of the compression stroke, and self-ignites.Diesel engine

The diesel engine (also known as a compression-ignition engine) is an internal combustion engine that uses the heat of compression to initiate ignition and burn the fuel that has been injected into the combustion chamber. This contrasts with spark-ignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to gasoline), which use a spark plug to ignite an air-fuel mixture.

The diesel engine has the highest thermal efficiency of any standard internal or external combustion engine due to its very high compression ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared to two-stroke non-direct-injection gasoline engines since unburnt fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) can have a thermal efficiency that exceeds 50%.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Diesel_engine" \l "cite_note-mhi-2" [2]Diesel engines are manufactured in two-stroke and four-stroke versions. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, trucks, heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s, the use of diesel engines in larger on-road and off-road vehicles in the USA increased. According to the British Society of Motor Manufacturing and Traders, the EU average for diesel cars account for 50% of the total sold, including 70% in France and 38% in the UK.[3]The world's largest diesel engine is currently a Wrtsil-Sulzer RTA96-C Common Rail marine diesel of about 84.42MW (113,210hp) at 102rpm[4] output.[5]Anemometer

An anemometer or windmeter is a device used for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any air speed measurement instrument used in meteorology or aerodynamics. The first known description of an anemometer was given by Leon Battista Alberti around 1450.[1]Anemometers can be divided into two classes: those that measure the wind's speed, and those that measure the wind's pressure; but as there is a close connection between the pressure and the speed, an anemometer designed for one will give information about both.

HistoryThe anemometer has changed little since its development in the 15th century. Leon Battista Alberti is said to have invented the first mechanical anemometer around 1450. In following centuries, numerous others, including Robert Hooke and the Mayans, developed their own versions, with some being mistakenly credited as the inventor.

Vane anemometersOne of the other forms of mechanical velocity anemometer is the vane anemometer. It may be described as a windmill or a propeller anemometer. Contrary to the Robinson anemometer, where the axis of rotation is vertical, the axis on the vane anemometer must be parallel to the direction of the wind and therefore horizontal. Furthermore, since the wind varies in direction and the axis has to follow its changes, a wind vane or some other contrivance to fulfill the same purpose must be employed.

Induction coil

An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil[1] after Heinrich Ruhmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Induction_coil" \l "cite_note-Collins-2" [2] To create the flux changes necessary to induce voltage in the secondary, the direct current in the primary is repeatedly interrupted by a vibrating mechanical contact called an interrupter.[1] Developed beginning in 1836 by Nicholas Callan and others,[1] the induction coil was the first type of transformer. They were widely used in x-ray machines,[3]

HYPERLINK "http://en.wikipedia.org/wiki/Induction_coil" \l "cite_note-Britannica-1" [1] spark-gap radio transmitters,[3]

HYPERLINK "http://en.wikipedia.org/wiki/Induction_coil" \l "cite_note-Britannica-1" [1] arc lighting and quack medical electrotherapy devices from the 1880s to the 1920s. Today their only use is as the ignition coils in internal combustion engines, and in physics education to demonstrate induction.

The term 'induction coil' is also used for a coil carrying high-frequency alternating current (AC), producing eddy currents to heat objects placed in the interior of the coil, in induction heating or zone melting equipment.

Construction and functionSee schematic diagram. An induction coil consists of two coils of insulated copper wire wound around a common iron core (M).[4]

HYPERLINK "http://en.wikipedia.org/wiki/Induction_coil" \l "cite_note-Britannica-1" [1] One coil, called the primary winding (P), is made from relatively few (tens or hundreds) turns of coarse wire.[4] The other coil, the secondary winding, (S) typically consists of many (thousands) turns of fine wire.[4]

HYPERLINK "http://en.wikipedia.org/wiki/Induction_coil" \l "cite_note-Britannica-1" [1]Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its development in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley, the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and the inventors were jointly awarded the 1956 Nobel Prize in Physics for their achievement.

HistoryThe thermionic triode, a vacuum tube invented in 1907, propelled the electronics age forward, enabling amplified radio technology and long-distance telephony. The triode, however, was a fragile device that consumed a lot of power. Physicist Julius Edgar Lilienfeld filed a patent for a field-effect transistor (FET) in Canada in 1925, which was intended to be a solid-state replacement for the triode.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Transistor" \l "cite_note-2" [2] Lilienfeld also filed identical patents in the United States in 1926[3] and 1928.[4]

HYPERLINK "http://en.wikipedia.org/wiki/Transistor" \l "cite_note-5" [5] However, Lilienfeld did not publish any research articles about his devices nor did his patents cite any specific examples of a working prototype. Dynamometer

A dynamometer or "dyno" for short, is a device for measuring force, torque, or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed

A dynamometer can also be used to determine the torque and power required to operate a driven machine such as a pump. In that case, a motoring or driving dynamometer is used. A dynamometer that is designed to be driven is called an absorption or passive dynamometer. A dynamometer that can either drive or absorb is called a universal or active dynamometer.

In addition to being used to determine the torque or power characteristics of a machine under test (MUT), dynamometers are employed in a number of other roles. In standard emissions testing cycles such as those defined by the United States Environmental Protection Agency (US EPA), dynamometers are used to provide simulated road loading of either the engine (using an engine dynamometer) or full powertrain (using a chassis dynamometer). In fact, beyond simple power and torque measurements, dynamometers can be used as part of a testbed for a variety of engine development activities, such as the calibration of engine management controllers, detailed investigations into combustion behavior, and tribology.

Voltmeter

A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter.

Voltmeters are made in a wide range of styles. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus. Portable instruments, usually equipped to also measure current and resistance in the form of a multimeter, are standard test instruments used in electrical and electronics work. Any measurement that can be converted to a voltage can be displayed on a meter that is suitably calibrated; for example, pressure, temperature, flow or level in a chemical process plant.

General purpose analog voltmeters may have an accuracy of a few percent of full scale, and are used with voltages from a fraction of a volt to several thousand volts. Digital meters can be made with high accuracy, typically better than 1%. Specially calibrated test instruments have higher accuracies, with laboratory instruments capable of measuring to accuracies of a few parts per million. Meters using amplifiers can measure tiny voltages of microvolts or less.

Speedometer

speedometer or a speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards.[1] Speedometers for other vehicles have specific names and use other means of sensing speed. For a boat, this is a pit log. For an aircraft, this is an airspeed indicator.

Charles Babbage is credited with creating an early type of a speedometer, which were usually fitted to locomotives.[2]

HYPERLINK "http://en.wikipedia.org/wiki/Speedometer" \l "cite_note-3" [3]The electric speedometer was invented by the Croatian Josip Belui[4]

HYPERLINK "http://en.wikipedia.org/wiki/Speedometer" \l "cite_note-5" [5] in 1888, and was originally called a velocimeter.

Eddy currenthe eddy current speedometer has been used for over a century and is still in widespread use. Until the 1980s and the appearance of electronic speedometers it was the only type commonly used.

Originally patented by a German, Otto Schulze on October 7, 1902,[6] it uses a rotating flexible cable usually driven by gearing linked to the output of the vehicle's transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.

Variometer

A variometer (also known as a rate of climb and descent Indicator (RCDI), rate-of-climb indicator, vertical speed indicator (VSI), or vertical velocity indicator (VVI)) is one of the flight instruments in an aircraft used to inform the pilot of the near instantaneous (rather than averaged) rate of descent or climb.[1] It can be calibrated in knots, feet per minute (101.333ft/min = 1kn) or metres per second, depending on country and type of aircraft.

In powered flight the pilot makes frequent use of the VSI to ascertain that level flight is being maintained, especially during turning maneuvers. In gliding, the instrument is used almost continuously during normal flight, often with an audible output, to inform the pilot of rising or sinking air. It is usual for gliders to be equipped with more than one type of variometer. The simpler type does not need an external source of power and can therefore be relied upon to function regardless of whether a battery or power source has been fitted.

DescriptionVariometers measure the rate of change of altitude by detecting the change in air pressure (static pressure) as altitude changes. A simple variometer can be constructed by adding a large reservoir (a thermos bottle) to augment the storage capacity of a common aircraft rate-of-climb instrument. In its simplest electronic form, the instrument consists of an air bottle connected to the external atmosphere through a sensitive air flow meter.Accelerometer

An accelerometer is a device that measures proper acceleration ("g-force"). Proper acceleration is not the same as coordinate acceleration (rate of change of velocity). For example, an accelerometer at rest on the surface of the Earth will measure an acceleration g= 9.81 m/s2 straight upwards. By contrast, accelerometers in free fall orbiting and accelerating due to the gravity of Earth will measure zero.

Accelerometers have multiple applications in industry and science. Highly sensitive accelerometers are components of inertial navigation systems for aircraft and missiles. Accelerometers are used to detect and monitor vibration in rotating machinery. Accelerometers are used in tablet computers and digital cameras so that images on screens are always displayed upright. Accelerometers are used in drones for flight stabilisation. Pairs of accelerometers extended over a region of space can be used to detect differences (gradients) in the proper accelerations of frames of references associated with those points.

Single- and multi-axis models of accelerometer are available to detect magnitude and direction of the proper acceleration (or g-force), as a vector quantity, and can be used to sense orientation (because direction of weight changes), coordinate acceleration (so long as it produces g-force or a change in g-force), vibration, shock, and falling in a resistive medium (a case where the proper acceleration changes, since it starts at zero, then increases). Micromachined accelerometers are increasingly present in portable electronic devices and video game controllers, to detect the position of the device or provide for game input.

Spectrometer

A spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.[1] The variable measured is most often the light's intensity but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a unit directly proportional to the photon energy, such as wavenumber or electron volts, which has a reciprocal relationship to wavelength. A spectrometer is used in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Spectrometer is a term that is applied to instruments that operate over a very wide range of wavelengths, from gamma rays and X-rays into the far infrared. If the instrument is designed to measure the spectrum in absolute units rather than relative units, then it is typically called a spectrophotometer. The majority of spectrophotometers are used in spectral regions near the visible spectrum.

In general, any particular instrument will operate over a small portion of this total range because of the different techniques used to measure different portions of the spectrum. Below optical frequencies (that is, at microwave and radio frequencies), the spectrum analyzer is a closely related electronic device.

SpectroscopesSpectroscopes are often used in astronomy and some branches of chemistry. Early spectroscopes were simply prisms with graduations marking wavelengths of light. Modern spectroscopes generally use a diffraction grating, a movable slit, and some kind of photodetector, all automated and controlled by a computer.Barometer

A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs, high pressure systems and frontal boundaries.

Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be transported from place to place matching the atmospheric pressure to the corresponding altitude, while a barometer is kept stationary and measures subtle pressure changes caused by weather. The main exception to this is ships at sea, which can use a barometer because their elevation does not change. Due to the presence of weather systems, aircraft altimeters may need to be adjusted as they fly between regions of varying normalized atmospheric pressure.

HistoryAlthough Evangelista Torricelli is universally credited with inventing the barometer in 1643,[1]

HYPERLINK "http://en.wikipedia.org/wiki/Barometer" \l "cite_note-http:.2F.2Fwww.barometerfair.com.2Fhistory_of_the_barometer.htm-2" [2]

HYPERLINK "http://en.wikipedia.org/wiki/Barometer" \l "cite_note-http:.2F.2Fwww.juliantrubin.com.2Fbigten.2Ftorricellibarometer.html-3" [3] historical documentation also suggests Gasparo Berti, an Italian mathematician and astronomer, unintentionally built a water barometer sometime between 1640 and 1643.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Barometer" \l "cite_note-4" [4] French scientist and philosopher Ren Descartes described the design of an experiment to determine atmospheric pressure as early as 1631, but there is no evidence that he built a working barometer at that time.Clamp meter

Minimum currentIs it true that clamp meters are limited to a minimum of about an amp? The preceding unsigned comment was added by Mickpc (talk contribs) .No. The current probes (a form of clamp meter) supplied by Tektronix are rated down to 1 milliamp.

It is true, however, that conventional clamp meters aren't very sensitive. One way around that is to wrap multiple turns of wire through the clamp, increasing the sensitivity n times (where n is the number of turns).

Bare wiresDoes the clamp have to clamp to bare wires or is insulated OK? The preceding unsigned comment was added by Cjm@drmconsulting.com (talk contribs) .Clamp meters are designed for use with insulated wires. They respond to the magnetic field around the wire. They may not be sufficiently insulated for use with bare wires and may be dangerous to use with bare wires or too near bare terminals where insulated wires are connected. --C J Cowie 13:34, 26 September 2006 (UTC)

Grammar & sentence structureA comma is not for separating two individual sentences. "Only one conductor is normally passed through the probe, if more than one conductor were..." is incorrect. "Only one conductor is normally passed through the probe." is a complete statement and should be ended with a period. "If more than one conductor were..."

Ohmmeter

An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current. Micro-ohmmeters (microhmmeter or microohmmeter) make low resistance measurements. Megohmmeters (aka megaohmmeter or in the case of a trademarked device Megger) measure large values of resistance. The unit of measurement for resistance is ohms.

The first ohmmeters were based on a type of meter movement known as a 'ratiometer'.[1]

HYPERLINK "http://en.wikipedia.org/wiki/Ohmmeter" \l "cite_note-2" [2] These were similar to the galvanometer type movement encountered in later instruments, but instead of hairsprings to supply a restoring force they used conducting 'ligaments' instead. These provided no net rotational force to the movement. Also, the movement was wound with two coils. One was connected via a series resistor to the battery supply. The second was connected to the same battery supply via a second resistor and the resistor under test. The indication on the meter was proportional to the ratio of the currents through the two coils. This ratio was determined by the magnitude of the resistor under test. The advantages of this arrangement were twofold. First, the indication of the resistance was completely independent of the battery voltage (as long as it actually produced some voltage) and no zero adjustment was required. Second, although the resistance scale was non linear, the scale remained correct over the full deflection range. By interchanging the two coils a second range was provided.

Wattmeter

The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements.

ElectrodynamicThe traditional analog wattmeter is an electrodynamic instrument. The device consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil.The current coils connected in series with the circuit, while the potential coil is connected in parallel. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate the measurement. A current flowing through the current coil generates an electromagnetic field around the coil. The strength of this field is proportional to the line current and in phase with it. The result of this arrangement is that on a dc circuit, the deflection of the needle is proportional to both the current (I) and the voltage (V), thus conforming to the equation P=VI.

For AC power, current and voltage may not be in phase, owing to the delaying effects of circuit inductance or capacitance. On an ac circuit the deflection is proportional to the average instantaneous product of voltage and current, thus measuring true power, P=VI cos . Here, cos represents the power factor which shows that the power transmitted may be less than the apparent power obtained by multiplying the readings of a voltmeter and ammeter in the same circuit.PAGE 28