1.
Capacitive displacement sensor
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Capacitive displacement sensors “are non-contact devices capable of high-resolution measurement of the position and/or change of position of any conductive target”. They are also able to measure the thickness or density of non-conductive materials and these types of sensors can be found in machining and manufacturing facilities around the world. Capacitance is a property which is created by applying an electrical charge to two conductive objects with a gap between them. A simple demonstration is two parallel plates of the same profile with a gap between them and a charge applied to them. There are two types of capacitive displacement sensing systems. One type is used to measure thicknesses of conductive materials, the other type measures thicknesses of non conductive materials or the level of a fluid. Therefore, the equation above can be simplified to, C ∝1 d Where α indicates a proportional relationship, due to this proportional relationship, a capacitive sensing system is able to measure changes in capacitance and translate these changes into distance measurements. The operation of the sensor for measuring thickness of materials can be thought of as two capacitors in series, with each having a different dielectric. The sum of the thicknesses of the two dielectric materials remains constant but the thickness of each can vary, the thickness of the material to be measured displaces the other dielectric. The gap is often an air gap, and the material has a higher dielectric, as the material gets thicker, the capacitance increases and is sensed by the system. A sensor for measuring fluid levels works as two capacitors in parallel with constant total area, again the difference in the dielectric constant of the fluid and the dielectric constant of air results in detectable changes in the capacitance between the conductive probes or plates. One of the more common applications of capacitive sensors is for precision positioning, capacitive displacement sensors can be used to measure the position of objects down to the nanometer level. This type of precise positioning is used in the industry where silicon wafers need to be positioned for exposure. Capacitive sensors are used to pre-focus the electron microscopes used in testing and examining the wafers. In the disc drive industry, capacitive displacement sensors are used to measure the runout of disc drive spindles, by knowing the exact runout of these spindles, disc drive manufacturers are able to determine the maximum amount of data that can be placed onto the drives. Capacitive sensors are used to ensure that disc drive platters are orthogonal to the spindle before data is written to them. Capacitive displacement sensors can be used to very precise thickness measurements. Capacitive displacement sensors operate by measuring changes in position, if the position of a reference part of known thickness is measured, other parts can be subsequently measured and the differences in position can be used to determine the thickness of these parts
2.
Electrical engineering
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Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics, and electromagnetism. This field first became an occupation in the later half of the 19th century after commercialization of the electric telegraph, the telephone. Subsequently, broadcasting and recording media made electronics part of daily life, the invention of the transistor, and later the integrated circuit, brought down the cost of electronics to the point they can be used in almost any household object. Electrical engineers typically hold a degree in engineering or electronic engineering. Practicing engineers may have professional certification and be members of a professional body, such bodies include the Institute of Electrical and Electronics Engineers and the Institution of Engineering and Technology. Electrical engineers work in a wide range of industries and the skills required are likewise variable. These range from basic circuit theory to the management skills required of a project manager, the tools and equipment that an individual engineer may need are similarly variable, ranging from a simple voltmeter to a top end analyzer to sophisticated design and manufacturing software. Electricity has been a subject of scientific interest since at least the early 17th century and he also designed the versorium, a device that detected the presence of statically charged objects. In the 19th century, research into the subject started to intensify, Electrical engineering became a profession in the later 19th century. Practitioners had created an electric telegraph network and the first professional electrical engineering institutions were founded in the UK. Over 50 years later, he joined the new Society of Telegraph Engineers where he was regarded by other members as the first of their cohort, Practical applications and advances in such fields created an increasing need for standardised units of measure. They led to the standardization of the units volt, ampere, coulomb, ohm, farad. This was achieved at a conference in Chicago in 1893. During these years, the study of electricity was considered to be a subfield of physics. Thats because early electrical technology was electromechanical in nature, the Technische Universität Darmstadt founded the worlds first department of electrical engineering in 1882. The first course in engineering was taught in 1883 in Cornell’s Sibley College of Mechanical Engineering. It was not until about 1885 that Cornell President Andrew Dickson White established the first Department of Electrical Engineering in the United States, in the same year, University College London founded the first chair of electrical engineering in Great Britain. Professor Mendell P. Weinbach at University of Missouri soon followed suit by establishing the engineering department in 1886
3.
Capacitive coupling
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Capacitive coupling is the transfer of energy within an electrical network or between distant networks by means of displacement current between circuit nodes, induced by the electric field. This coupling can have an intentional or accidental effect, in its simplest implementation, capacitive coupling is achieved by placing a capacitor between two nodes. In its general form the coupling is described by a capacitance matrix Cij, where Cii are self-capacitance coefficients and Cij i≠j are mutual capacitance coefficients. In analog circuits, a capacitor is used to connect two circuits such that only the AC signal from the first circuit can pass through to the next while DC is blocked. This technique helps to isolate the DC bias settings of the two coupled circuits, capacitive coupling is also known as AC coupling and the capacitor used for the purpose is also known as a DC-blocking capacitor. Capacitive coupling has the disadvantage of degrading the low performance of a system containing capacitively coupled units. So for adequate low frequency response, the capacitors used must have high capacitance ratings and they should be high enough that the reactance of each is at most a tenth of the input impedance of each stage, at the lowest frequency of interest. Coupling capacitors can also introduce nonlinear distortion at low frequencies and this is not an issue at high frequencies because the voltage across the capacitor stays very close to zero. This is avoided by choosing capacitor types that have low voltage coefficient and these disadvantages of capacitively coupling DC-biased transistor amplifier circuits are largely minimized in directly coupled designs. AC coupling is widely used in digital circuits to transmit digital signals with a zero DC component. For this reason, most modern line codes are designed to produce DC-balanced waveforms, the most common classes of DC-balanced line codes are constant-weight codes and paired-disparity codes. A gimmick loop is a type of capacitive coupler, two closely spaced strands of wire. It provides capacitive coupling of a few picofarads between two nodes, sometimes the wires are twisted together for physical stability. Capacitive coupling is often unintended, such as the capacitance between two wires or PCB traces that are next to each other, often one signal can capacitively couple with another and cause what appears to be noise. Breadboards are particularly prone to these issues due to the pieces of metal that line every row creating a several-picofarad capacitor between lines. To prototype high-frequency or high-gain analog circuits, often the circuits are built over a plane so that the signals couple to ground more than to each other. If a high-gain amplifiers output capacitively couples to its input it often becomes an electronic oscillator, one rule of thumb says that drivers should be able to drive 25 pF of capacitance which allows for PCB traces up to 0.30 meters. Capacitance and Uses of Capacitors Howard Johnson, When to use AC coupling, DC Blocking Capacitor Value Texas Instruments, AC-Coupling Between Differential LVPECL, LVDS, HSTL, and CML
4.
Dielectric
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A dielectric material is an electrical insulator that can be polarized by an applied electric field. Because of dielectric polarization, positive charges are displaced toward the field and this creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, the study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important for explaining various phenomena in electronics, optics, solid-state physics, while the term insulator implies low electrical conduction, dielectric typically means materials with a high polarizability. The latter is expressed by a called the relative permittivity. The term insulator is generally used to indicate electrical obstruction while the term dielectric is used to indicate the energy storing capacity of the material, a common example of a dielectric is the electrically insulating material between the metallic plates of a capacitor. The polarization of the dielectric by the electric field increases the capacitors surface charge for the given electric field strength. The term dielectric was coined by William Whewell in response to a request from Michael Faraday, a perfect dielectric is a material with zero electrical conductivity, thus exhibiting only a displacement current, therefore it stores and returns electrical energy as if it were an ideal capacitor. The electric susceptibility χe of a material is a measure of how easily it polarizes in response to an electric field. This, in turn, determines the electric permittivity of the material and thus many other phenomena in that medium. The susceptibility of a medium is related to its relative permittivity εr by χ e = ε r −1, so in the case of a vacuum, χ e =0. The electric displacement D is related to the polarization density P by D = ε0 E + P = ε0 E = ε r ε0 E, in general, a material cannot polarize instantaneously in response to an applied field. The more general formulation as a function of time is P = ε0 ∫ − ∞ t χ e E d t ′ and that is, the polarization is a convolution of the electric field at previous times with time-dependent susceptibility given by χe. The upper limit of this integral can be extended to infinity as well if one defines χe =0 for Δt <0, an instantaneous response corresponds to Dirac delta function susceptibility χe = χeδ. It is more convenient in a system to take the Fourier transform. Due to the theorem, the integral becomes a simple product. Note the simple frequency dependence of the susceptibility, or equivalently the permittivity, the shape of the susceptibility with respect to frequency characterizes the dispersion properties of the material. In the classical approach to the model, a material is made up of atoms
5.
Hygrometer
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A hygrometer /haɪˈɡrɒmᵻtər/ is an instrument used for measuring the moisture content in the atmosphere. Humidity measurement instruments usually rely on measurements of some other quantity such as temperature, pressure, by calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use temperature of condensation, or changes in electrical capacitance or resistance to measure humidity differences, the first crude hygrometer was invented by Leonardo da Vinci in 1480 and a more modern version was created by polymath Johann Heinrich Lambert in 1755. The metal-paper coil hygrometer is very useful for giving an indication of humidity changes. It appears most often in very inexpensive devices, and its accuracy is limited, in these devices, water vapour is absorbed by a salt-impregnated paper strip attached to a metal coil, causing the coil to change shape. These changes cause an indication on a dial and these devices use a human or animal hair under tension. The hair is hygroscopic, its length changes with humidity, in the late 1700s, such devices were called by some scientists hygroscopes, that word is no longer in current use, but hygroscopic and hygroscopy, which derive from it, still are. The traditional folk art known as a weather house works on this principle. Whale bone and other materials may be used in place of hair, in 1783, Swiss physicist and geologist Horace Bénédict de Saussure built the first hair-tension hygrometer using human hair. The pulley is connected to an index which moves over a graduated scale, the instrument can be made more sensitive by removing oils from the hair, such as by first soaking the hair in diethyl ether. A psychrometer, or wet-and-dry-bulb thermometer, consists of two thermometers, one that is dry and one that is kept moist with distilled water on a sock or wick. When the air temperature is below freezing, however, the wet-bulb is covered with a coating of ice. Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer, relative humidity can also be determined by locating the intersection of the wet and dry-bulb temperatures on a psychrometric chart. The two thermometers coincide when the air is saturated, and the greater the difference the drier the air. Psychrometers are commonly used in meteorology, and in the HVAC industry for proper refrigerant charging of residential and commercial air conditioning systems, a whirling psychrometer uses the same principle, but the two thermometers are fitted into a device that resembles a ratchet or football rattle. Dew point is the temperature at which a sample of moist air at constant pressure reaches water vapor saturation, at this saturation temperature, further cooling results in condensation of water. Chilled mirror dewpoint hygrometers are some of the most precise instruments commonly available and they use a chilled mirror and optoelectronic mechanism to detect condensation on the mirrors surface. The temperature of the mirror is controlled by electronic feedback to maintain an equilibrium between evaporation and condensation, thus closely measuring the dew point temperature
6.
Level sensor
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Level sensors detect the level of liquids and other fluids and fluidized solids, including slurries, granular materials, and powders that exhibit an upper free surface. Substances that flow become essentially horizontal in their containers because of gravity whereas most bulk solids pile at an angle of repose to a peak, the substance to be measured can be inside a container or can be in its natural form. The level measurement can be continuous or point values. Generally the latter detect levels that are high or low. There are many physical and application variables that affect the selection of the optimal level monitoring method for industrial and commercial processes, in short, level sensors are one of the very important sensors and play very important role in variety of consumer/ industrial applications. As with other type of sensors, level sensors are available or can be designed using variety of sensing principles, selection of an appropriate type of sensor suiting to the application requirement is very important. A variety of sensors are available for point level detection of solids and these include vibrating, rotating paddle, mechanical, microwave, capacitance, optical, pulsed-ultrasonic and ultrasonic level sensors. These detect levels of fine powders, fine powders. With proper selection of vibration frequency and suitable sensitivity adjustments, they can sense the level of highly fluidized powders. Single-probe vibrating level sensors are ideal for bulk powder level, since only one sensing element contacts the powder, bridging between two probe elements is eliminated and media build-up is minimized. The vibration of the probe tends to eliminate build-up of material on the probe element, vibrating level sensors are not affected by dust, static-charge build-up from dielectric powders, or changes in conductivity, temperature, pressure, humidity or moisture content. Tuning-fork style vibration sensors are another alternative and they tend to be less costly, but are prone to material buildup between the tines, Rotating paddle level sensors are a very old and established technique for bulk solid point level indication. The technique uses a low-speed gear motor that rotates a paddle wheel, when the paddle is stalled by solid materials, the motor is rotated on its shaft by its own torque until a flange mounted on the motor contacts a mechanical switch. The paddle can be constructed from a variety of materials, build-up may occur if the process material becomes tacky because of high moisture levels or high ambient humidity in the hopper. For materials with low weight per unit volume such as Pearlite, Bentonite or fly ash, special paddle designs. Fine particles or dust must be prevented from penetrating the shaft bearings and motor by proper placement of the paddle in the hopper or bin, an RF Admittance level sensor uses a rod probe and RF source to measures the change in admittance. The probe is driven through a coaxial cable to eliminate the effects of changing cable capacitance to ground. When the level changes around the probe, a change in the di-electric is observed
7.
Accelerometer
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An accelerometer is a device that measures proper acceleration, proper acceleration is not the same as coordinate acceleration. For example, an accelerometer at rest on the surface of the Earth will measure an acceleration due to Earths gravity, by contrast, accelerometers in free fall 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, coordinated accelerometers can be used to measure differences in proper acceleration, particularly gravity, over their separation in space, i. e. gradient of the gravitational field. This gravity gradiometry is useful because absolute gravity is a weak effect, 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. An accelerometer measures proper acceleration, which is the acceleration it experiences relative to freefall and is the acceleration felt by people and objects. Put another way, at any point in spacetime the equivalence principle guarantees the existence of an inertial frame. Such accelerations are popularly denoted g-force, i. e. in comparison to standard gravity, an accelerometer at rest relative to the Earths surface will indicate approximately 1 g upwards, because any point on the Earths surface is accelerating upwards relative to the local inertial frame. The reason for the appearance of an offset is Einsteins equivalence principle. For similar reasons, an accelerometer will read zero during any type of free fall and this includes use in a coasting spaceship in deep space far from any mass, a spaceship orbiting the Earth, an airplane in a parabolic zero-g arc, or any free-fall in vacuum. Another example is free-fall at a high altitude that atmospheric effects can be neglected. However this does not include a fall in air resistance produces drag forces that reduce the acceleration. At terminal velocity the accelerometer will indicate 1 g acceleration upwards, Acceleration is quantified in the SI unit metres per second per second, in the cgs unit gal, or popularly in terms of standard gravity. For the practical purpose of finding the acceleration of objects with respect to the Earth, such as for use in a navigation system. This can be obtained either by calibrating the device at rest, conceptually, an accelerometer behaves as a damped mass on a spring. When the accelerometer experiences an acceleration, the mass is displaced to the point that the spring is able to accelerate the mass at the rate as the casing. The displacement is measured to give the acceleration
8.
Touchpad
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Touchpads are a common feature of laptop computers, and are also used as a substitute for a mouse where desk space is scarce. Because they vary in size, they can also be found on personal digital assistants, wireless touchpads are also available as detached accessories. Touchpads operate in one of several ways, including capacitive sensing, the most common technology used as of 2010 entails sensing the capacitive virtual ground effect of a finger, or the capacitance between sensors. Capacitance-based touchpads will not sense the tip of a pencil or other similar implement, gloved fingers may also be problematic. While touchpads, like touchscreens, are able to sense absolute position, resolution is limited by their size, hardware buttons equivalent to a standard mouses left and right buttons are positioned below, above, or beside the touchpad. Some touchpads and associated device driver software may interpret tapping the pad as a click, Tactile touchpads allow for clicking and dragging by incorporating button functionality into the surface of the touchpad itself. To select, one presses down on the touchpad instead of a physical button, to drag, instead performing the click-and-a-half technique, one presses down while on the object, drags without releasing pressure and lets go when done. Touchpad drivers can also allow the use of fingers to facilitate the other mouse buttons. Some touchpads have hotspots, locations on the used for functionality beyond a mouse. Many touchpads use two-finger dragging for scrolling, also, some touchpad drivers support tap zones, regions where a tap will execute a function, for example, pausing a media player or launching an application. All of these functions are implemented in the device driver software. By 1982 Apollo desktop computers were equipped with a touchpad on the side of the keyboard. Introduced a year later, the Gavilan SC included a touchpad above its keyboard, a touchpad was first developed for Psions MC 200/400/600/WORD Series in 1989. Olivetti and Triumph-Adler introduced the first laptops with touchpad in 1992. Cirque introduced the first widely available touchpad, branded as GlidePoint, in 1994. Apple Inc introduced touchpads to the laptop in the PowerBook series in 1994, using Cirque’s GlidePoint technology. Another early adopter of the GlidePoint pointing device was Sharp, later, Synaptics introduced their touchpad into the marketplace, branded the TouchPad. Epson was an early adopter of this product, as touchpads began to be introduced in laptops in the 1990s, there was often confusion as to what the product should be called. No consistent term was used, and references varied, such as, glidepoint, touch sensitive input device, touchpad, trackpad, users were often presented the option to purchase a pointing stick, touchpad, or trackball
9.
Computer mouse
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A computer mouse is a pointing device that detects two-dimensional motion relative to a surface. This motion is typically translated into the motion of a pointer on a display, physically, a mouse consists of an object held in ones hand, with one or more buttons. Mice often also other elements, such as touch surfaces and wheels. The earliest known publication of the mouse as referring to a computer pointing device is in Bill Englishs July 1965 publication. The plural for the rodent is always mice in modern usage. The plural of a mouse is mouses and mice according to most dictionaries. The first recorded usage is mice, the online Oxford Dictionaries cites a 1984 use. The trackball, a pointing device, was invented in 1944 by Ralph Benjamin as part of a World War II-era fire-control radar plotting system called Comprehensive Display System. Benjamin was then working for the British Royal Navy Scientific Service, Benjamins project used analog computers to calculate the future position of target aircraft based on several initial input points provided by a user with a joystick. Benjamin felt that a more elegant input device was needed and invented what they called a ball for this purpose. The device was patented in 1947, but only a prototype using a ball rolling on two rubber-coated wheels was ever built, and the device was kept as a military secret. Another early trackball was built by British electrical engineer Kenyon Taylor in collaboration with Tom Cranston, Taylor was part of the original Ferranti Canada, working on the Royal Canadian Navys DATAR system in 1952. DATAR was similar in concept to Benjamins display, the trackball used four disks to pick up motion, two each for the X and Y directions. When the ball was rolled, the pickup discs spun and contacts on their outer rim made periodic contact with wires, by counting the pulses, the physical movement of the ball could be determined. A digital computer calculated the tracks and sent the data to other ships in a task force using pulse-code modulation radio signals. This trackball used a standard Canadian five-pin bowling ball and it was not patented, since it was a secret military project. Douglas Engelbart of the Stanford Research Institute has been credited in published books by Thierry Bardini, Paul Ceruzzi, Howard Rheingold, Engelbart was also recognized as such in various obituary titles after his death in July 2013. That November, while attending a conference on computer graphics in Reno, Nevada, Engelbart began to ponder how to adapt the underlying principles of the planimeter to X-Y coordinate input
10.
MP3 player
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An MP3 player or Digital Audio Player is an electronic device that can play digital audio files. It is a type of Portable Media Player, the term MP3 player is a misnomer, as most players play more than the MP3 file format. Since the MP3 format is used, almost all players can play that format. In addition, there are many digital audio formats. Some formats are proprietary, such as MP3, Windows Media Audio, some of these formats also may incorporate digital rights management, such as WMA DRM, which are often part of paid download sites. Other formats are patent-free or otherwise open, such as Vorbis, FLAC, in 1981, Kane Kramer filed for a UK patent for the IXI, the first Digital Audio Player. UK patent 2115996 was issued in 1985, and U. S, patent 4,667,088 was issued in 1987. Plans were made for a 10-minute stereo memory card and the system was at one time fitted with a drive which would have enabled over an hour of recorded digital music. However, in 1988 Kramers failure to raise the £60,000 required to renew the patent meant it entering the public domain, but he still owns the designs. In the year 1987 a German Company by the name of Fraunhofer-Gesellschaft started the program for coding music with the high quality. The project was controlled by an expert in mathematics and electronics, the first MP3 player was developed by SaeHan Information Systems in 1997. Nevertheless, the first one on the American market was the Eiger Labs F10, a 32MB portable that appeared in the summer of 1998. It was a basic unit and wasnt user expandable, though owners could upgrade the memory to 64MB by sending the player back to Eiger Labs with a check for $69.00 + $7.95 shipping. The second MP3 player needed was the Rio PMP300 from Diamond Multimedia, the Rio was a big success during the Christmas 1998 season as sales significantly exceeded expectations, spurring interest and investment in digital music. Eiger Labs and Diamond and went on to establish a new segment in the audio player market. Other early MP3 portables include Sensory Sciences Rave MP2100, the I-Jam IJ-100 and these portables were small and light, but only held enough memory to hold around 7 to 20 songs at normal 128kbit/s compression rates. As more users migrated to Win 98 by 2000, all players went USB, at the end of 1999, a company called Remote Solutions significantly broke that barrier by utilizing a laptop drive for song storage rather than low capacity flash memory. The Personal Jukebox had 4. 8GB, which held about 1200 songs and this segment eventually became the dominant type of digital music player
11.
Mobile phone
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A mobile phone is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the systems of a mobile phone operator. Most modern mobile telephone services use a network architecture, and, therefore. Mobile phones which offer these and more general computing capabilities are referred to as smartphones, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. In 1983, the DynaTAC 8000x was the first commercially available mobile phone. From 1983 to 2014, worldwide mobile phone subscriptions grew to seven billion, penetrating 100% of the global population. In first quarter of 2016, the top smartphone manufacturers were Samsung, Apple, a handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917, Finnish inventor Eric Tigerstedt filed a patent for a pocket-size folding telephone with a thin carbon microphone. Early predecessors of cellular phones included analog radio communications from ships, the race to create truly portable telephone devices began after World War II, with developments taking place in many countries. These 0G systems were not cellular, supported few simultaneous calls, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. The first commercial automated cellular network was launched in Japan by Nippon Telegraph and this was followed in 1981 by the simultaneous launch of the Nordic Mobile Telephone system in Denmark, Finland, Norway, and Sweden. Several other countries followed in the early to mid-1980s. These first-generation systems could support far more simultaneous calls but still used analog cellular technology, in 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone. In 1991, the digital cellular technology was launched in Finland by Radiolinja on the GSM standard. This sparked competition in the sector as the new operators challenged the incumbent 1G network operators, ten years later, in 2001, the third generation was launched in Japan by NTT DoCoMo on the WCDMA standard. This was followed by 3. 5G, 3G+ or turbo 3G enhancements based on the high-speed packet access family, allowing UMTS networks to have data transfer speeds. By 2009, it had become clear that, at point, 3G networks would be overwhelmed by the growth of bandwidth-intensive applications. Consequently, the industry began looking to data-optimized fourth-generation technologies, with the promise of speed improvements up to ten-fold over existing 3G technologies
12.
Tablet computer
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Tablets often come equipped with sensors, including digital cameras, a microphone, and an accelerometer so images on screens are always displayed upright. The touchscreen display uses the recognition of finger or stylus gestures to replace the mouse, trackpad, tablets are typically larger than smartphones or personal digital assistants with screens 7 inches or larger, measured diagonally. However much of a tablets functionality resembles that of a modern smartphone, tablets can be classified according to the presence and physical appearance of keyboards. Slates and booklets do not have a keyboard, and usually accept text. Hybrids, convertibles, and 2-in-1s do have physical keyboards, yet they also make use of virtual keyboards. Some 2-in-1s have processors and operating systems like a full laptop, most tablets can use separate keyboards connected using Bluetooth. The format was conceptualized in the century and prototyped and developed in the last two decades of that century. In April 2010, Apple released the iPad, the first mass-market tablet to achieve widespread popularity, thereafter in the 2010s, tablets rapidly rose in ubiquity and became a large product category used for both personal and workplace applications. The tablet computer and its operating system began with the development of pen computing. Throughout the 20th century devices with these characteristics have been imagined and created whether as blueprints, prototypes, a device more powerful than todays tablets appeared briefly in Jerry Pournelle and Larry Nivens The Mote in Gods Eye. Adults could also use a Dynabook, but the audience was children. In 1992, Atari showed developers the Stylus, later renamed ST-Pad, the ST-Pad was based on the TOS/GEM Atari ST Platform and prototyped early handwriting recognition. Shiraz Shivjis company Momentus demonstrated in the time a failed x86 MS-DOS based Pen Computer with its own GUI. In 1994, the European Union initiated the NewsPad project, inspired by Clarke, Acorn Computers developed and delivered an ARM-based touch screen tablet computer for this program, branding it the NewsPad, the project ended in 1997. During the November 2000 COMDEX, Microsoft used the term Tablet PC to describe a prototype handheld device they were demonstrating, all three products were based on extended versions of the MS-DOS operating system. In 1992, IBM announced and shipped to developers the 2521 ThinkPad, also based on PenPoint was AT&Ts EO Personal Communicator from 1993, which ran on AT&Ts own hardware, including their own AT&T Hobbit CPU. Apple Computer launched the Apple Newton personal digital assistant in 1993 and it utilised Apples own new Newton OS, initially running on hardware manufactured by Motorola and incorporating an ARM CPU, that Apple had specifically co-developed with Acorn Computers. The operating system and platform design were later licensed to Sharp and Digital Ocean, in 1996, Palm, Inc. released the first of the Palm OS based PalmPilot touch and stylus based PDA, the touch based devices initially incorporating a Motorola Dragonball CPU
13.
Touchscreen
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A touchscreen is a input and output device normally layered on the top of an electronic visual display of an information processing system. A user can give input or control the processing system through simple or multi-touch gestures by touching the screen with a special stylus and/or one or more fingers. Some touchscreens use ordinary or specially coated gloves to work while others may only work using a special stylus/pen, the user can use the touchscreen to react to what is displayed and to control how it is displayed, for example, zooming to increase the text size. The touchscreen enables the user to interact directly with what is displayed, rather using a mouse, touchpad. Touchscreens are common in such as game consoles, personal computers, tablet computers, electronic voting machines, point of sale systems. They can also be attached to computers or, as terminals and they also play a prominent role in the design of digital appliances such as personal digital assistants and some e-readers. The popularity of smartphones, tablets, and many types of appliances is driving the demand and acceptance of common touchscreens for portable. The application of technology for air traffic control was described in an article published in 1968. Frank Beck and Bent Stumpe, engineers from CERN, developed a transparent touchscreen in the early 1970s, then manufactured by CERN, it was put to use in 1973. A resistive touchscreen was developed by American inventor George Samuel Hurst, the first version was produced in 1982. This arrangement can sense any fingertip-sized opaque object in close proximity to the screen, a similar touchscreen was used on the HP-150 starting in 1983, this was one of the worlds earliest commercial touchscreen computers. HP mounted their infrared transmitters and receivers around the bezel of a 9 Sony Cathode Ray Tube, in 1984, Fujitsu released a touch pad for the Micro 16, to deal with the complexity of kanji characters, which were stored as tiled graphics. In 1985, Sega released the Terebi Oekaki, also known as the Sega Graphic Board, for the SG-1000 video game console and it consisted of a plastic pen and a plastic board with a transparent window where the pen presses are detected. It was used primarily for a software application. A graphic touch tablet was released for the Sega AI Computer in 1986, touch-sensitive Control-Display Units were evaluated for commercial aircraft flight decks in the early 1980s. In 1985, the University of Toronto group including Bill Buxton developed a tablet that used capacitance rather than bulky camera-based optical sensing systems. In 1986, the first graphical point of sale software was demonstrated on the 16-bit Atari 520ST color computer and it featured a color touchscreen widget-driven interface. In 1987, Casio launched the Casio PB-1000 pocket computer with a touchscreen consisting of a 4x4 matrix, until 1988 touchscreens had the bad reputation of being imprecise
14.
Indium tin oxide
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Indium tin oxide is a ternary composition of indium, tin and oxygen in varying proportions. Depending on the content, it can either be described as a ceramic or alloy. Indium tin oxide is encountered as an oxygen-saturated composition with a formulation of 74% In, 18% O2. Oxygen-saturated compositions are so typical, that unsaturated compositions are termed oxygen-deficient ITO and it is transparent and colorless in thin layers, while in bulk form it is yellowish to grey. In the infrared region of the spectrum it acts as a metal-like mirror, thin films of indium tin oxide are most commonly deposited on surfaces by physical vapor deposition. Often used is electron beam evaporation, or a range of sputter deposition techniques, indium tin oxide is an optoelectronic material that is applied widely in both research and industry. ITO can be used for applications, such as flat-panel displays, smart windows, polymer-based electronics, thin film photovoltaics. Moreover, ITO thin films for glass substrates can be helpful for glass windows to conserve energy, ITO green tapes are utilized for the production of lamps that are electroluminescent, functional, and fully flexible. ITO is often used to make transparent conductive coating for displays such as liquid crystal displays, flat panel displays, plasma displays, touch panels, thin films of ITO are also used in organic light-emitting diodes, solar cells, antistatic coatings and EMI shieldings. In organic light-emitting diodes, ITO is used as the anode, ITO films deposited on windshields are used for defrosting aircraft windshields. The heat is generated by applying voltage across the film, ITO is also used for various optical coatings, most notably infrared-reflecting coatings for automotive, and sodium vapor lamp glasses. Other uses include gas sensors, antireflection coatings, electrowetting on dielectrics, ITO is also used as the IR reflector for low-e window panes. ITO was also used as a coating in the later Kodak DCS cameras, starting with the Kodak DCS520. ITO thin film strain gauges can operate at temperatures up to 1400 °C and can be used in environments, such as gas turbines, jet engines. ITO is a heavily doped n-type semiconductor with a bandgap of around 4 eV. Because of the bandgap, it is transparent in the visible part of the spectrum and its extinction coefficient, k. In the ultraviolet, it is opaque, so k is non zero in the UV spectral range. It is also opaque in the infrared and infrared, because of free carrier absorption
15.
Ground plane
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In electrical engineering, a ground plane is an electrically conductive surface, usually connected to electrical ground. The term has two different meanings in separate areas of electrical engineering, in telecommunication, a ground plane is a flat or nearly flat horizontal conducting surface that serves as part of an antenna, to reflect the radio waves from the other antenna elements. The plane does not necessarily have to be connected to ground, Ground plane shape and size play major roles in determining its radiation characteristics including gain. To function as a plane, the conducting surface must be at least a quarter of the wavelength of the radio waves in size. In lower frequency antennas, such as the mast radiators used for broadcast antennas, for higher frequency antennas, in the VHF or UHF range, the ground plane can be smaller, and metal disks, screens and wires are used as ground planes. At upper VHF and UHF, the skin of a car or aircraft can serve as a ground plane for whip antennas projecting from it. In microstrip antennas and printed monopole antennas an area of copper foil on the side of a printed circuit board serves as a ground plane. The ground plane doesnt have to be a continuous surface, in the ground plane antenna style whip antenna, the plane consists of several wires λ/4 long radiating from the base of a quarter-wave whip antenna. The radio waves from an element that reflect off a ground plane appear to come from a mirror image of the antenna located on the other side of the ground plane. In a monopole antenna, the pattern of the monopole plus the virtual image antenna make it appear as a two element center-fed dipole antenna. So a monopole mounted over a ground plane has a radiation pattern identical to a dipole antenna. The feedline from the transmitter or receiver is connected between the end of the monopole element and the ground plane. The ground plane must have good conductivity, any resistance in the plane is in series with the antenna. A ground plane on a circuit board is a large area or layer of copper foil connected to the circuits ground point. It serves as the path for current from many different components. A ground plane is made as large as possible, covering most of the area of the PCB which is not occupied by circuit traces. In multilayer PCBs, it is often a separate layer covering the entire board, when digital circuits switch state, large current pulses flow from the active devices through the ground circuit. If the power supply and ground traces have significant impedance, the drop across them may create noise voltage pulses that disturb other parts of the circuit
16.
Parasitic capacitance
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All actual circuit elements such as inductors, diodes, and transistors have internal capacitance, which can cause their behavior to depart from that of ideal circuit elements. The parasitic capacitance between the turns of an inductor or other component is often described as self-capacitance. However, self-capacitance of an object is a different phenomenon. When two conductors at different potentials are close to one another, they are affected by each others electric field, changing the potential v between the conductors requires a current i into or out of the conductors to charge or discharge them. I = C d v d t where C is the capacitance between the conductors, for example, an inductor often acts as though it includes a parallel capacitor, because of its closely spaced windings. When a potential difference exists across the coil, wires lying adjacent to each other are at different potentials and they act like the plates of a capacitor, and store charge. Any change in the voltage across the coil requires extra current to charge and discharge these small capacitors, coils for high frequencies are often basket-wound to minimise parasitic capacitance. At low frequencies parasitic capacitance can usually be ignored, but in high frequency circuits it can be a major problem. In amplifier circuits with extended frequency response, parasitic capacitance between the output and the input can act as a path, causing the circuit to oscillate at high frequency. These unwanted oscillations are called parasitic oscillations, in high frequency amplifiers, parasitic capacitance can combine with stray inductance such as component leads to form resonant circuits, also leading to parasitic oscillations. In all inductors, the parasitic capacitance will resonate with the inductance at some frequency to make the inductor self-resonant. Above this frequency, the inductor actually has capacitive reactance, the capacitance of the load circuit attached to the output of op amps can reduce their bandwidth. This Miller capacitance is the factor limiting the high frequency performance of active devices like transistors. The diagram, right, illustrates how Miller capacitance comes about, suppose the amplifier shown is an ideal inverting amplifier with voltage gain of A, and Z = C is a capacitance between its input and output. The voltage gain of modern transistors can be 10 -100 or even higher, so this is a significant limitation
17.
Electric field
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An electric field is a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge, by an infinitesimal test charge at that point. Electric fields are created by electric charges and can be induced by time-varying magnetic fields, the electric field combines with the magnetic field to form the electromagnetic field. The electric field, E, at a point is defined as the force, F. A particle of charge q would be subject to a force F = q E and its SI units are newtons per coulomb or, equivalently, volts per metre, which in terms of SI base units are kg⋅m⋅s−3⋅A−1. Electric fields are caused by electric charges or varying magnetic fields, in the special case of a steady state, the Maxwell-Faraday inductive effect disappears. The resulting two equations, taken together, are equivalent to Coulombs law, written as E =14 π ε0 ∫ d r ′ ρ r − r ′ | r − r ′ |3 for a charge density ρ. Notice that ε0, the permittivity of vacuum, must be substituted if charges are considered in non-empty media, the equations of electromagnetism are best described in a continuous description. A charge q located at r 0 can be described mathematically as a charge density ρ = q δ, conversely, a charge distribution can be approximated by many small point charges. Electric fields satisfy the principle, because Maxwells equations are linear. This principle is useful to calculate the field created by point charges. Q n are stationary in space at r 1, r 2, in that case, Coulombs law fully describes the field. If a system is static, such that magnetic fields are not time-varying, then by Faradays law, in this case, one can define an electric potential, that is, a function Φ such that E = − ∇ Φ. This is analogous to the gravitational potential, Coulombs law, which describes the interaction of electric charges, F = q = q E is similar to Newtons law of universal gravitation, F = m = m g. This suggests similarities between the electric field E and the gravitational field g, or their associated potentials, mass is sometimes called gravitational charge because of that similarity. Electrostatic and gravitational forces both are central, conservative and obey an inverse-square law, a uniform field is one in which the electric field is constant at every point. It can be approximated by placing two conducting plates parallel to other and maintaining a voltage between them, it is only an approximation because of boundary effects. Assuming infinite planes, the magnitude of the electric field E is, electrodynamic fields are E-fields which do change with time, for instance when charges are in motion. The electric field cannot be described independently of the field in that case
18.
Voltage
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Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential energy between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against an electric field to move the test charge between two points. This is measured in units of volts, voltage can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three. A voltmeter can be used to measure the voltage between two points in a system, often a reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy or lost, used, given two points in space, x A and x B, voltage is the difference in electric potential between those two points. Electric potential must be distinguished from electric energy by noting that the potential is a per-unit-charge quantity. Like mechanical potential energy, the zero of electric potential can be chosen at any point, so the difference in potential, i. e. the voltage, is the quantity which is physically meaningful. The voltage between point A to point B is equal to the work which would have to be done, per unit charge, against or by the electric field to move the charge from A to B. The voltage between the two ends of a path is the energy required to move a small electric charge along that path. Mathematically this is expressed as the integral of the electric field. In the general case, both an electric field and a dynamic electromagnetic field must be included in determining the voltage between two points. Historically this quantity has also called tension and pressure. Pressure is now obsolete but tension is used, for example within the phrase high tension which is commonly used in thermionic valve based electronics. Voltage is defined so that negatively charged objects are pulled towards higher voltages, therefore, the conventional current in a wire or resistor always flows from higher voltage to lower voltage. Current can flow from lower voltage to higher voltage, but only when a source of energy is present to push it against the electric field. This is the case within any electric power source, for example, inside a battery, chemical reactions provide the energy needed for ion current to flow from the negative to the positive terminal. The electric field is not the only factor determining charge flow in a material, the electric potential of a material is not even a well defined quantity, since it varies on the subatomic scale. A more convenient definition of voltage can be found instead in the concept of Fermi level, in this case the voltage between two bodies is the thermodynamic work required to move a unit of charge between them
19.
Electrical conductor
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In physics and electrical engineering, a conductor is an object or type of material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors, Electrical current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases. In order for current to flow, it is not necessary for one charged particle to travel from the producing the current to that consuming it. Instead, the particle simply needs to nudge its neighbor a finite amount who will nudge its neighbor and on and on until a particle is nudged into the consumer. Essentially what is occurring here is a chain of momentum transfer between mobile charge carriers, the Drude model of conduction describes this process more rigorously. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents, the resistance of a given conductor depends on the material it is made of, and on its dimensions. For a given material, the resistance is proportional to the cross-sectional area. For example, a copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a material, the resistance is proportional to the length, for example. The resistance R and conductance G of a conductor of uniform cross section, therefore, the resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals, ρ =1 / σ, resistivity is a measure of the materials ability to oppose electric current. This formula is not exact, It assumes the current density is uniform in the conductor. However, this still provides a good approximation for long thin conductors such as wires. Another situation this formula is not exact for is with alternating current, then, the geometrical cross-section is different from the effective cross-section in which current actually flows, so the resistance is higher than expected. Similarly, if two conductors are each other carrying AC current, their resistances increase due to the proximity effect. Aside from the geometry of the wire, temperature also has a significant effect on the efficacy of conductors, temperature affects conductors in two main ways, the first is that materials may expand under the application of heat. The amount that the material will expand is governed by the expansion coefficient specific to the material. Such an expansion will change the geometry of the conductor and therefore its characteristic resistance, however, this effect is generally small, on the order of 10−6
20.
Capacitor
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A capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance, a capacitor was therefore historically first known as an electric condenser. The physical form and construction of practical capacitors vary widely and many types are in common use. Most capacitors contain at least two electrical conductors often in the form of plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, the nonconducting dielectric acts to increase the capacitors charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, a capacitor does not dissipate energy. No current actually flows through the dielectric, instead, the effect is a displacement of charges through the source circuit, if the condition is maintained sufficiently long, this displacement current through the battery ceases. However, if a voltage is applied across the leads of the capacitor. Capacitance is defined as the ratio of the charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units is the farad, capacitance values of typical capacitors for use in general electronics range from about 1 pF to about 1 mF. The capacitance of a capacitor is proportional to the area of the plates. In practice, the dielectric between the plates passes a small amount of leakage current and it has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance, Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies, in resonant circuits they tune radios to particular frequencies. In electric power systems, they stabilize voltage and power flow. The property of energy storage in capacitors was exploited as dynamic memory in digital computers. Von Kleists hand and the water acted as conductors, and the jar as a dielectric, von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine
21.
Controller (computing)
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In computing and especially in computer hardware, a controller is a chip, an expansion card, or a stand-alone device that interfaces with a peripheral device. This may be a link between two parts of a computer or a controller on a device that manages the operation of that device. The term is used in the opposite sense to refer to a device by which the user controls the operation of the computer. In desktop computers the controller may be a plug in board, in mainframes the controller is usually either a separate device attached to a channel or integrated into the peripheral. Early desktop computers such as the IMSAI8080 used expansion boards for all controllers, disk controller, often integrated into modern disk drives. Disk array controller, also known as RAID controller, a type of storage controller Flash controller, or SSD controller, terminal Access Controller In IBM terminology a controller is a device that decodes the command and effects the operation of the device. In most mainframe systems a device-independent channel usually attaches to the CPU, the functions performed by the control unit are similar to the functions performed by a device driver program on smaller systems. Some devices have integrated control units, which are logically discrete but are included with the rather than requiring a separate box. Often a control unit can attach to multiple channels connected to a single or multiple systems
22.
Capacitance
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Capacitance is the ability of a body to store an electric charge. There are two related notions of capacitance--self capacitance and mutual capacitance--that are usually both designated by the same term, capacitance. Any object that can be electrically charged exhibits self capacitance, a material with a large self capacitance holds more electric charge at a given voltage, than one with low capacitance. The notion of mutual capacitance is important for understanding the operations of the capacitor. The capacitance is a function only of the geometry of the design, for many dielectric materials, the permittivity and thus the capacitance, is independent of the potential difference between the conductors and the total charge on them. The SI unit of capacitance is the farad, named after the English physicist Michael Faraday, a 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates. In electrical circuits, the capacitance is usually a shorthand for the mutual capacitance between two adjacent conductors, such as the two plates of a capacitor. It is actually mutual capacitance between the turns of the coil and is a form of stray, or parasitic capacitance. This self-capacitance is an important consideration at high frequencies and it changes the impedance of the coil and gives rise to parallel resonance. In many applications this is an effect and sets an upper frequency limit for the correct operation of the circuit. The inverse of capacitance is called elastance, the unit of elastance is the daraf, but is not recognised by SI. A common form is a capacitor, which consists of two conductive plates insulated from each other, usually sandwiching a dielectric material. In a parallel capacitor, capacitance is very nearly proportional to the surface area of the conductor plates. If the charges on the plates are +q and −q, and V gives the voltage between the plates, then the capacitance C is given by C = q V. which gives the voltage/current relationship I = C d V d t. Historically, a farad was regarded as a large unit. Its subdivisions were invariably used, namely the microfarad, nanofarad and picofarad, more recently, technology has advanced such that capacitors of 1 farad and greater can be constructed in a structure little larger than a coin battery. Such capacitors are used for energy storage replacing more traditional batteries. The energy stored in a capacitor is found by integrating the work W, W charging =12 C V2 The discussion above is limited to the case of two conducting plates, although of arbitrary size and shape
23.
Calibration
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Calibration in measurement technology and metrology is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, strictly, the term calibration means just the act of comparison, and does not include any subsequent adjustment. The calibration standard is normally traceable to a national standard held by a National Metrological Institute and this definition states that the calibration process is purely a comparison, but introduces the concept of Measurement uncertainty in relating the accuracies of the device under test and the standard. The increasing need for accuracy and uncertainty and the need to have consistent. In many countries a National Metrology Institute will exist which will maintain primary standards of measurement which will be used to provide traceability to customers instruments by calibration. The NMI supports the metrological infrastructure in that country by establishing an unbroken chain, examples of National Metrology Institutes are NPL in the UK, NIST in the United States, PTB in Germany and many others. This may be done by national standards laboratories operated by the government or by private firms offering metrology services, quality management systems call for an effective metrology system which includes formal, periodic, and documented calibration of all measuring instruments. ISO9000 and ISO17025 standards require that these actions are to a high level. To communicate the quality of a calibration the calibration value is often accompanied by a traceable uncertainty statement to a confidence level. This is evaluated through careful uncertainty analysis, some times a DFS is required to operate machinery in a degraded state. Whenever this does happen, it must be in writing and authorized by a manager with the assistance of a calibration technician. Measuring devices and instruments are categorized according to the quantities they are designed to measure. These vary internationally, e. g. NIST 150-2G in the U. S. the standard instrument for each test device varies accordingly, e. g. a dead weight tester for pressure gauge calibration and a dry block temperature tester for temperature gauge calibration. g. This is the perception of the instruments end-user, however, very few instruments can be adjusted to exactly match the standards they are compared to. For the vast majority of calibrations, the process is actually the comparison of an unknown to a known. The calibration process begins with the design of the instrument that needs to be calibrated. The design has to be able to hold a calibration through its calibration interval, in other words, the design has to be capable of measurements that are within engineering tolerance when used within the stated environmental conditions over some reasonable period of time. Having a design with these characteristics increases the likelihood of the measuring instruments performing as expected
24.
Interactive kiosk
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Interactive kiosks are typically placed in high foot traffic settings such as shops, hotel lobbies or airports. Integration of technology allows kiosks to perform a range of functions. Customised components such as coin hoppers, bill acceptors, card readers, the first self-service, interactive kiosk was developed in 1977 at the University of Illinois at Urbana-Champaign by a pre-med student, Murray Lappe. The content was created on the PLATO computer system and accessible by plasma touch screen interface, the plasma display panel was invented at the University of Illinois at Urbana-Champaign by Donald L. Bitzer. Lappes kiosk, called The Plato Hotline allowed students and visitors to find movies, maps, directories, bus schedules, the interactive kiosk was created, manufactured and customized by ByVideo Inc. of Sunnyvale, CA. The network of over 600 kiosks provided images and video promotion for customers who wished to purchase shoes that were not available in the retail location, style, size and color could be selected, and the product paid for on the kiosk itself. The transaction was sent to the Florsheim mainframe in St, Louis, MO, via dialup lines, the hardware were designed and built by ByVideo, while other components were sourced from other vendors. The videodisc material was created quarterly by ByVideo at Florsheims direction and this kiosk network operated for over 6 years in Florsheim retail locations. In 1991, the first commercial kiosk with internet connection was displayed at Comdex, the application was for locating missing children. The first true documentation of a kiosk was the 1995 report by Los Alamos National Laboratory which detailed what the interactive kiosk consisted of and this was first announced on comp. infosystems. kiosks by Arthur the original usenet moderator. In 1997, KioskCom was launched to provide a tradeshow for organizations looking to deploy interactive self-service kiosks and these tradeshows occur twice a year, and offer companies education and demonstrations for successful self-service deployments. The first company to launch an interactive kiosk program was Imperial Multimedia in 2007. Todays kiosks bring together the classic vending machine with high-tech communications and complex robotic, such interactive kiosks can include self-checkout lanes, e-ticketing, information and wayfinding, and vending. Electronic kiosks have become a part of the retail landscape as users embrace technology in their daily lives. One such example of a retail kiosk business is Redbox. Redbox was formerly a subsidiary of Outerwall, Inc. another well known company popular for Coinstar kiosks, the aesthetic and functional design of interactive kiosks is a key element that drives user adoption, overall up-time and affordability. There are many factors to consider designing a interactive kiosk including, Aesthetic design, The design of the enclosure is often the driving factor in user adoption. Manufacturing volume, This will determine which manufacturing processes are appropriate to use, Kiosk software, The interactive function of the kiosk hardware is largely determined by the software program and kiosk software configuration
25.
Etching (microfabrication)
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Etching is used in microfabrication to chemically remove layers from the surface of a wafer during manufacturing. Etching is an important process module, and every wafer undergoes many etching steps before it is complete. For many etch steps, part of the wafer is protected from the etchant by a material which resists etching. In some cases, the material is a photoresist which has been patterned using photolithography. Other situations require a more durable mask, such as silicon nitride, if the etch is intended to make a cavity in a material, the depth of the cavity may be controlled approximately using the etching time and the known etch rate. More often, though, etching must entirely remove the top layer of a multilayer structure, the etching systems ability to do this depends on the ratio of etch rates in the two materials. Some etches undercut the masking layer and form cavities with sloping sidewalls, the distance of undercutting is called bias. Etchants with large bias are called isotropic, because they erode the substrate equally in all directions, Modern processes greatly prefer anisotropic etches, because they produce sharp, well-controlled features. The two fundamental types of etchants are liquid-phase and plasma-phase, each of these exists in several varieties. The first etching processes used liquid-phase etchants, the wafer can be immersed in a bath of etchant, which must be agitated to achieve good process control. For instance, buffered hydrofluoric acid is used commonly to etch silicon dioxide over a silicon substrate, different specialised etchants can be used to characterise the surface etched. Wet etchants are usually isotropic, which leads to large bias when etching thick films and they also require the disposal of large amounts of toxic waste. For these reasons, they are used in state-of-the-art processes. However, the developer used for photoresist resembles wet etching. As an alternative to immersion, single wafer machines use the Bernoulli principle to employ a gas to cushion and it can be done to either the front side or back side. The etch chemistry is dispensed on the top side when in the machine and this etch method is particularly effective just before backend processing, where wafers are normally very much thinner after wafer backgrinding, and very sensitive to thermal or mechanical stress. Etching a thin layer of even a few micrometres will remove microcracks produced during backgrinding resulting in the wafer having dramatically increased strength, some wet etchants etch crystalline materials at very different rates depending upon which crystal face is exposed. In single-crystal materials, this effect can allow very high anisotropy, the term crystallographic etching is synonymous with anisotropic etching along crystal planes
26.
Cartesian coordinate system
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Each reference line is called a coordinate axis or just axis of the system, and the point where they meet is its origin, usually at ordered pair. The coordinates can also be defined as the positions of the projections of the point onto the two axis, expressed as signed distances from the origin. One can use the principle to specify the position of any point in three-dimensional space by three Cartesian coordinates, its signed distances to three mutually perpendicular planes. In general, n Cartesian coordinates specify the point in an n-dimensional Euclidean space for any dimension n and these coordinates are equal, up to sign, to distances from the point to n mutually perpendicular hyperplanes. The invention of Cartesian coordinates in the 17th century by René Descartes revolutionized mathematics by providing the first systematic link between Euclidean geometry and algebra. Using the Cartesian coordinate system, geometric shapes can be described by Cartesian equations, algebraic equations involving the coordinates of the points lying on the shape. For example, a circle of radius 2, centered at the origin of the plane, a familiar example is the concept of the graph of a function. Cartesian coordinates are also tools for most applied disciplines that deal with geometry, including astronomy, physics, engineering. They are the most common system used in computer graphics, computer-aided geometric design. Nicole Oresme, a French cleric and friend of the Dauphin of the 14th Century, used similar to Cartesian coordinates well before the time of Descartes. The adjective Cartesian refers to the French mathematician and philosopher René Descartes who published this idea in 1637 and it was independently discovered by Pierre de Fermat, who also worked in three dimensions, although Fermat did not publish the discovery. Both authors used a single axis in their treatments and have a length measured in reference to this axis. The concept of using a pair of axes was introduced later, after Descartes La Géométrie was translated into Latin in 1649 by Frans van Schooten and these commentators introduced several concepts while trying to clarify the ideas contained in Descartes work. Many other coordinate systems have developed since Descartes, such as the polar coordinates for the plane. The development of the Cartesian coordinate system would play a role in the development of the Calculus by Isaac Newton. The two-coordinate description of the plane was later generalized into the concept of vector spaces. Choosing a Cartesian coordinate system for a one-dimensional space – that is, for a straight line—involves choosing a point O of the line, a unit of length, and an orientation for the line. An orientation chooses which of the two half-lines determined by O is the positive, and which is negative, we say that the line is oriented from the negative half towards the positive half
27.
Electrode
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An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit. The word was coined by William Whewell at the request of the scientist Michael Faraday from the Greek words elektron, meaning amber, and hodos, an electrode in an electrochemical cell is referred to as either an anode or a cathode. The anode is now defined as the electrode at which electrons leave the cell and oxidation occurs, each electrode may become either the anode or the cathode depending on the direction of current through the cell. A bipolar electrode is an electrode that functions as the anode of one cell, a primary cell is a special type of electrochemical cell in which the reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode, the cell can be discharged but not recharged. A secondary cell, for example a rechargeable battery, is a cell in which the reactions are reversible. When the cell is being charged, the anode becomes the positive and this is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a cell, with the anode as the negative. In a vacuum tube or a semiconductor having polarity the anode is the positive electrode, the electrons enter the device through the cathode and exit the device through the anode. Many devices have other electrodes to control operation, e. g. base, gate, control grid. In a three-electrode cell, an electrode, also called an auxiliary electrode, is used only to make a connection to the electrolyte so that a current can be applied to the working electrode. The counter electrode is made of an inert material, such as a noble metal or graphite. In arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together. Depending upon the process, the electrode is either consumable, in the case of gas metal arc welding or shielded metal arc welding, or non-consumable, such as in gas tungsten arc welding. For a direct current system the weld rod or stick may be a cathode for a filling type weld or an anode for other welding processes, for an alternating current arc welder the welding electrode would not be considered an anode or cathode. Electrodes are used to provide current through nonmetal objects to them in numerous ways. These electrodes are used for advanced purposes in research and investigation
28.
Pixel
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The address of a pixel corresponds to its physical coordinates. LCD pixels are manufactured in a grid, and are often represented using dots or squares. Each pixel is a sample of an image, more samples typically provide more accurate representations of the original. The intensity of each pixel is variable, in color imaging systems, a color is typically represented by three or four component intensities such as red, green, and blue, or cyan, magenta, yellow, and black. The word pixel is based on a contraction of pix and el, the word pixel was first published in 1965 by Frederic C. Billingsley of JPL, to describe the elements of video images from space probes to the Moon. Billingsley had learned the word from Keith E. McFarland, at the Link Division of General Precision in Palo Alto, McFarland said simply it was in use at the time. The word is a combination of pix, for picture, the word pix appeared in Variety magazine headlines in 1932, as an abbreviation for the word pictures, in reference to movies. By 1938, pix was being used in reference to pictures by photojournalists. The concept of a picture element dates to the earliest days of television, some authors explain pixel as picture cell, as early as 1972. In graphics and in image and video processing, pel is often used instead of pixel, for example, IBM used it in their Technical Reference for the original PC. A pixel is generally thought of as the smallest single component of a digital image, however, the definition is highly context-sensitive. For example, there can be printed pixels in a page, or pixels carried by electronic signals, or represented by digital values, or pixels on a display device, or pixels in a digital camera. This list is not exhaustive and, depending on context, synonyms include pel, sample, byte, bit, dot, Pixels can be used as a unit of measure such as,2400 pixels per inch,640 pixels per line, or spaced 10 pixels apart. For example, a high-quality photographic image may be printed with 600 ppi on a 1200 dpi inkjet printer, even higher dpi numbers, such as the 4800 dpi quoted by printer manufacturers since 2002, do not mean much in terms of achievable resolution. The more pixels used to represent an image, the closer the result can resemble the original, the number of pixels in an image is sometimes called the resolution, though resolution has a more specific definition.3 megapixels. The pixels, or color samples, that form an image may or may not be in one-to-one correspondence with screen pixels. In computing, a composed of pixels is known as a bitmapped image or a raster image
29.
Liquid-crystal display
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A liquid-crystal display is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome and they use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements. LCDs are used in a range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays. Small LCD screens are common in consumer devices such as digital cameras, watches, calculators. LCD screens are used on consumer electronics products such as DVD players, video game devices. LCD screens have replaced heavy, bulky cathode ray tube displays in all applications. LCD screens are available in a range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to huge. Since LCD screens do not use phosphors, they do not suffer image burn-in when an image is displayed on a screen for a long time. LCDs are, however, susceptible to image persistence, the LCD screen is more energy-efficient and can be disposed of more safely than a CRT can. Its low electrical power consumption enables it to be used in battery-powered electronic equipment more efficiently than CRTs can be, by 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes. Without the liquid crystal between the filters, light passing through the first filter would be blocked by the second polarizer. Before an electric field is applied, the orientation of the molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic device, the surface alignment directions at the two electrodes are perpendicular to other, and so the molecules arrange themselves in a helical structure. This induces the rotation of the polarization of the incident light, and this light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, color LCD systems use the same technique, with color filters used to generate red, green, and blue pixels. The optical effect of a TN device in the state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage. When no image is displayed, different arrangements are used, for this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers
30.
Point of sale
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The point of sale or point of purchase is the time and place where a retail transaction is completed. It is also the point at which a customer makes a payment to the merchant in exchange for goods or after provision of a service. After receiving payment, the merchant may issue a receipt for the transaction, which is usually printed, to calculate the amount owed by a customer, the merchant may use any of a variety of aids available, such as weighing scales, barcode scanners, and cash registers. To make a payment, payment terminals, touch screens, the point of sale is often referred to as the point of service because it is not just a point of sale but also a point of return or customer order. Additionally, current POS terminal software may include features to cater for different functionality, such as inventory management, CRM, financials. Businesses are increasingly adopting POS systems and one of the most obvious, selling prices are linked to the product code of an item when adding stock, so the cashier merely needs to scan this code to process a sale. If there is a change, this can also be easily done through the inventory window. Other advantages include ability to implement various types of discounts, a loyalty scheme for customers, retailers and marketers will often refer to the area around the checkout instead as the point of purchase when they are discussing it from the retailers perspective. This is particularly the case when planning and designing the area as well as considering a marketing strategy. Nevertheless, it is the term POS system rather than retail management system that is in vogue among both end-users and vendors, early electronic cash registers were controlled with proprietary software and were limited in function and communication capability. This system was the first commercial use of technology, peer-to-peer communications, local area network simultaneous backup. By mid-1974, it was installed in Pathmark stores in New Jersey, one of the first microprocessor-controlled cash register systems was built by William Brobeck and Associates in 1974, for McDonalds Restaurants. It used the Intel 8008, an early microprocessor. By pressing the button, a second or third order could be worked on while the first transaction was in progress, when the customer was ready to pay, the button would calculate the bill, including sales tax for almost any jurisdiction in the United States. This made it accurate for McDonalds and very convenient for the servers, up to eight devices were connected to one of two interconnected computers so that printed reports, prices, and taxes could be handled from any desired device by putting it into Manager Mode. In addition to the memory, accuracy was enhanced by having three copies of all important data with many numbers stored only as multiples of 3. Should one computer fail, the other could handle the entire store, in 1986, Gene Mosher introduced the first graphical point of sale software featuring a touchscreen interface under the ViewTouch trademark on the 16-bit Atari 520ST color computer. It featured a color touchscreen widget-driven interface that allowed configuration of widgets representing menu items without low level programming, the ViewTouch point of sale software was first demonstrated in public at Fall Comdex,1986, in Las Vegas Nevada to large crowds visiting the Atari Computer booth
31.
Multi-touch
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In computing, multi-touch is technology that enables a surface to recognize the presence of more than one or more than two points of contact with the surface. The origins of multitouch began at CERN, MIT, University of Toronto, Carnegie Mellon University, the term multi-touch was popularized in 2007 by Apple, though it was in use as early as 1985. This plural-point awareness may be used to implement additional functionality, such as pinch to zoom or to activate certain subroutines attached to predefined gestures, the use of touchscreen technology to control electronic devices pre-dates multi-touch technology and the personal computer. Early synthesizer and electronic instrument builders like Hugh Le Caine and Robert Moog experimented with using touch-sensitive capacitance sensors to control the sounds made by their instruments, early touchscreens only registered one point of touch at a time. On-screen keyboards were thus awkward to use, because key-rollover and holding down a key while typing another were not possible. An exception was a multi-touch reconfigurable touchscreen keyboard/display developed at the Massachusetts Institute of Technology in the early 1970s and this technology was used to develop a new type of human machine interface for the control room of the Super Proton Synchrotron particle accelerator. In a handwritten note dated 11 March 1972, Stumpe presented his proposed solution – a capacitive touch screen with a number of programmable buttons presented on a display. The capacitors were to consist of fine lines etched in copper on a sheet of glass – fine enough, in the final device, a simple lacquer coating prevented the fingers from actually touching the capacitors. In 1976, MIT described a keyboard with variable graphics capable of multi-touch detection, in the early 1980s, The University of Torontos Input Research Group were among the earliest to explore the software side of multi-touch input systems. A1982 system at the University of Toronto used a panel with a camera placed behind the glass. When a finger or several fingers pressed on the glass, the camera would detect the action as one or more spots on an otherwise white background. Since the size of a dot was dependent on pressure, the system was somewhat pressure-sensitive as well, of note, this system was input only and not able to display graphics. In 1983, Bell Labs at Murray Hill published a discussion of touch-screen based interfaces. By 1984, both Bell Labs and Carnegie Mellon University had working multi-touch-screen prototypes – both input and graphics – that could respond interactively in response to multiple finger inputs, the Bell Labs system was based on capacitive coupling of fingers, whereas the CMU system was optical. In 1985, the canonical multitouch pinch-to-zoom gesture was demonstrated, with coordinated graphics, an advance occurred in 1991, when Pierre Wellner published a paper on his multi-touch Digital Desk, which supported multi-finger and pinching motions. Various companies expanded upon these inventions in the beginning of the twenty-first century, the company Fingerworks developed various multi-touch technologies between 1999 and 2005, including Touchstream keyboards and the iGesture Pad. Several studies of technology were published in the early 2000s by Alan Hedge, professor of human factors. Apple acquired Fingerworks and its technology in 2005
32.
Relaxation oscillator
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In electronics a relaxation oscillator is a nonlinear electronic oscillator circuit that produces a nonsinusoidal repetitive output signal, such as a triangle wave or square wave. The period of the oscillator depends on the constant of the capacitor or inductor circuit. The active device switches abruptly between charging and discharging modes, and thus produces a discontinuously changing repetitive waveform, the period of a relaxation oscillator is mainly determined by the relaxation time constant. Relaxation oscillations are a type of cycle and are studied in nonlinear control theory. The first relaxation oscillator circuit, the astable multivibrator, was invented by Henri Abraham, thus there is only one ramp in the output waveform which takes up virtually the entire period. The voltage across the capacitor is a wave, while the current through the switching device is a sequence of short pulses. Astable multivibrator, In this type the capacitor is charged and discharged slowly through a resistor, so the output waveform consists of two parts, an increasing ramp and a decreasing ramp. The voltage generated by the capacitor is a waveform, while the voltage from the switching device is a square wave. Relaxation oscillators are used to produce low frequency signals for such applications as blinking lights. They are also used in voltage controlled oscillators, inverters and switching power supplies, dual-slope analog to digital converters, however they have more phase noise and poorer frequency stability than linear oscillators. The capacitor is charged by the source causing the voltage across the capacitor to rise. The threshold device does not conduct at all until the voltage reaches its threshold voltage. It then increases heavily its conductance in an avalanche-like manner because of the inherent positive feedback, when the voltage across the capacitor drops to some lower threshold voltage, the device stops conducting and the capacitor begins charging again, and the cycle repeats ad infinitum. If the threshold element is a lamp, the circuit also provides a flash of light with each discharge of the capacitor. This lamp example is depicted below in the circuit used to describe the Pearson–Anson effect. The discharging duration can be extended by connecting an additional resistor in series to the threshold element, the two resistors form a voltage divider, so, the additional resistor has to have low enough resistance to reach the low threshold. A similar relaxation oscillator can be built with a 555 timer IC that takes the place of the bulb above. That is, when a capacitor is charged to a design value
33.
RC circuit
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A resistor–capacitor circuit, or RC filter or RC network, is an electric circuit composed of resistors and capacitors driven by a voltage or current source. A first order RC circuit is composed of one resistor and one capacitor and is the simplest type of RC circuit, charge transport behaviour in various complex systems, including battery anodes and fuel cells can be described using models of many-element RC networks. RC circuits can be used to filter a signal by blocking certain frequencies, the two most common RC filters are the high-pass filters and low-pass filters, band-pass filters and band-stop filters usually require RLC filters, though crude ones can be made with RC filters. There are three basic, linear passive lumped analog circuit components, the resistor, the capacitor, and these may be combined in the RC circuit, the RL circuit, the LC circuit, and the RLC circuit, with the acronyms indicating which components are used. These circuits, among them, exhibit a number of important types of behaviour that are fundamental to much of analog electronics. In particular, they are able to act as passive filters and this article considers the RC circuit, in both series and parallel forms, as shown in the diagrams below. The simplest RC circuit is a capacitor and a resistor in parallel, when a circuit consists of only a charged capacitor and a resistor, the capacitor will discharge its stored energy through the resistor. The voltage across the capacitor, which is dependent, can be found by using Kirchhoffs current law. This results in the differential equation C d V d t + V R =0. Solving this equation for V yields the formula for exponential decay, V = V0 e − t R C, the time required for the voltage to fall to V0/e is called the RC time constant and is given by τ = R C. Sinusoidal steady state is a case in which the input voltage consists of a pure sinusoid. As a result, σ =0 and the impedance becomes Z C = − j ω C, the transfer function from the input voltage to the voltage across the capacitor is H C = V C V i n =11 + R C s. Similarly, the function from the input to the voltage across the resistor is H R = V R V i n = R C s 1 + R C s. Both transfer functions have a pole located at s = −1 R C. In addition, the function for the resistor has a zero located at the origin. These expressions together may be substituted into the expression for the phasor representing the output. The current in the circuit is the same everywhere since the circuit is in series, the impulse response for each voltage is the inverse Laplace transform of the corresponding transfer function. It represents the response of the circuit to an input consisting of an impulse or Dirac delta function
34.
LC circuit
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The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuits resonant frequency. LC circuits are used either for generating signals at a particular frequency and they are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers. An LC circuit is a model since it assumes there is no dissipation of energy due to resistance. Any practical implementation of an LC circuit will always include loss resulting from small but non-zero resistance within the components, the purpose of an LC circuit is usually to oscillate with minimal damping, so the resistance is made as low as possible. While no practical circuit is without losses, it is instructive to study this ideal form of the circuit to gain understanding. For a circuit model incorporating resistance, see RLC circuit, the two-element LC circuit described above is the simplest type of inductor-capacitor network. It is also referred to as a second order LC circuit to distinguish it more complicated LC networks with more inductors and capacitors. Such LC networks with more than two reactances may have more than one resonant frequency, the order of the network is the order of the rational function describing the network in the complex frequency variable s. Generally, the order is equal to the number of L and C elements in the circuit, an LC circuit, oscillating at its natural resonant frequency, can store electrical energy. A capacitor stores energy in the field between its plates, depending on the voltage across it, and an inductor stores energy in its magnetic field. If an inductor is connected across a capacitor, current will start to flow through the inductor, building up a magnetic field around it. Eventually all the charge on the capacitor will be gone and the voltage across it will reach zero, however, the current will continue, because inductors resist changes in current. The current will begin to charge the capacitor with a voltage of opposite polarity to its original charge. Due to Faradays law, the EMF which drives the current is caused by a decrease in the magnetic field, when the magnetic field is completely dissipated the current will stop and the charge will again be stored in the capacitor, with the opposite polarity as before. Then the cycle will begin again, with the current flowing in the direction through the inductor. The charge flows back and forth between the plates of the capacitor, through the inductor, the energy oscillates back and forth between the capacitor and the inductor until internal resistance makes the oscillations die out. In most applications the tuned circuit is part of a circuit which applies alternating current to it. If the frequency of the current is the circuits natural resonant frequency
35.
Time constant
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In physics and engineering, the time constant, usually denoted by the Greek letter τ, is the parameter characterizing the response to a step input of a first-order, linear time-invariant system. The time constant is the characteristic unit of a first-order LTI system. In the time domain, the choice to explore the time response is through the step response to a step input. Other examples include time constant used in systems for integral and derivative action controllers. Time constants are a feature of the system analysis for thermal systems. In an increasing system, the constant is the time for the systems step response to reach 1 −1 / e ≈63.2 % of its final value. For this reason, the constant is longer than the half-life. First order LTI systems are characterized by the differential equation τ d V d t + V = f where τ represents the decay constant. The right-hand side is the function f describing an external driving function of time. This behavior is referred to as an exponential function. The time τ is referred to as the constant and can be used to indicate how rapidly an exponential function decays. Here, t = time V0 = initial value, in case 4, after five time constants the function reaches a value less than 1% of its original. Suppose the forcing function is chosen as sinusoidal so, d V d t +1 τ V = f = A e j ω t. For long times the decaying exponentials become negligible and the so-called steady-state solution or long-time solution is, the magnitude of this response is, | V ∞ | = A1 τ1 /2 = A11 +2. By convention, the bandwidth of system is the frequency where |V∞|2 drops to half-value. This is the usual convention, defined as the frequency range where power drops by less than half. Using the frequency in hertz, rather than radians/s, f 3 d B =12 π τ. The notation f3dB stems from the expression of power in decibels, thus, the time constant determines the bandwidth of this system
36.
Wheatstone bridge
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A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of a bridge is its ability to provide extremely accurate measurements. Its operation is similar to the original potentiometer, the Wheatstone bridge was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridges initial uses was for the purpose of soils analysis, in the figure, R x is the unknown resistance to be measured, R1, R2, and R3 are resistors of known resistance and the resistance of R2 is adjustable. If the bridge is unbalanced, the direction of the current indicates whether R2 is too high or too low, R2 is varied until there is no current through the galvanometer, which then reads zero. Detecting zero current with a galvanometer can be done to extremely high accuracy, therefore, if R1, R2, and R3 are known to high precision, then R x can be measured to high precision. Very small changes in R x disrupt the balance and are readily detected and this setup is frequently used in strain gauge and resistance thermometer measurements, as it is usually faster to read a voltage level off a meter than to adjust a resistance to zero the voltage. The equation for this is, V G = V s where VG is the voltage of node D relative to node B, the Wheatstone bridge illustrates the concept of a difference measurement, which can be extremely accurate. Variations on the Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities, such as the amount of gases in a sample. The Kelvin bridge was adapted from the Wheatstone bridge for measuring very low resistances. The concept was extended to alternating current measurements by James Clerk Maxwell in 1865, the Wheatstone bridge is the fundamental bridge, but there are other modifications that can be made to measure various kinds of resistances when the fundamental Wheatstone bridge is not suitable. Some of the modifications are, Carey Foster bridge, for measuring small resistances Kelvin bridge, for measuring small four-terminal resistances Maxwell bridge, Wheatstone Bridge – Interactive Tutorial National High Magnetic Field Laboratory Test Set I-49
37.
Stylus
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A stylus, plural styli or styluses, is a writing utensil, or a small tool for some other form of marking or shaping, for example in pottery. It can also be an accessory that is used to assist in navigating or providing more precision when using touchscreens. It usually refers to a narrow elongated staff, similar to a ballpoint pen. Many styluses are heavily curved to be more easily. Another widely used writing tool is the used by blind users in conjunction with the slate for punching out the dots in Braille. Styluses were first used by the ancient Mesopotamians in order to write in cuneiform, cuneiform was entirely based on the wedge-shaped mark that the end of a cut reed made when pushed into a clay tablet, from Latin cuneus = wedge. The linear nature of the writing was also dictated by the use of the stylus, in Western Europe styluses were widely used until the late Middle Ages. For learning purposes the stylus was gradually replaced by a writing slate, from the mid-14th century improved water-powered paper mills produced large and cheap quantities of paper and the wax tablet and stylus disappeared completely from daily life. A different suggestion is that the word does not derive from the Greek word στῦλος and it signifies, An iron instrument, resembling a pencil in size and shape, used for writing upon waxed tablets. Thus, vertere stilum means to erase, and hence to correct, there exists minor controversy about the correct pluralization of stylus. Some assert that stylus is a loanword from Latin and should be pluralised as styli. However, stylus is an English word based on the Latin word stilus, occasionally the pluralisation stylii is seen. Styluses are still used in arts and crafts. Example situations, rubbing off dry transfer letters, tracing designs onto a new surface with carbon paper, styluses are also used to engrave into materials like metal or clay. Styluses are used to make dots as found in folk art, oaxaca dot art is created using styluses. In the sound recording industry, a stylus is a phonograph or gramophone needle used to play back sound on gramophone records, several technologies were used to record the sounds, beginning with wax cylinders, almost half a century before the invention of the magnetic cartridge. Nowadays mostly vinyl records are used, when playing the record, the stylus is placed in the grooves of the record. By then spinning the record, the start to vibrate caused by the shape of the grooves
38.
Noise (electronics)
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In electronics, noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits. Noise generated by electronic devices varies greatly as it is produced by different effects. In communication systems, noise is an error or undesired random disturbance of an information signal. The noise is a summation of unwanted or disturbing energy from natural, Noise is, however, typically distinguished from interference, for example in the signal-to-noise ratio, signal-to-interference ratio and signal-to-noise plus interference ratio measures. While noise is generally unwanted, it can serve a purpose in some applications. Johnson–Nyquist noise is unavoidable, and generated by the thermal motion of charge carriers, inside an electrical conductor. Thermal noise is white, meaning that its power spectral density is nearly equal throughout the frequency spectrum. The amplitude of the signal has very nearly a Gaussian probability density function, a communication system affected by thermal noise is often modeled as an additive white Gaussian noise channel. If electrons flow across a barrier, then they have discrete arrival times and those discrete arrivals exhibit shot noise. The output of a noise generator is easily set by the current. Typically, the barrier in a diode is used, shot noise in electronic devices results from unavoidable random statistical fluctuations of the electric current when the charge carriers traverse a gap. The current is a flow of charges, and the fluctuation in the arrivals of those charges creates shot noise. Shot noise is similar to the created by rain falling on a tin roof. The flow of rain may be constant, but the raindrops arrive discretely. The shot noise assumes independent arrivals, vacuum tubes have shot noise because the electrons randomly leave the cathode and arrive at the anode. A tube may not exhibit the full shot noise effect, the presence of a space charge tends to smooth out the arrival times. Conductors and resistors typically do not exhibit shot noise because the electrons thermalize and move diffusively within the material, shot noise has been demonstrated in mesoscopic resistors when the size of the resistive element becomes shorter than the electron-phonon scattering length. Flicker noise, also known as 1/f noise, is a signal or process with a spectrum that falls off steadily into the higher frequencies
39.
Stylus (computing)
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In computing, a stylus is a small pen-shaped instrument that is used to input commands to a computer screen, mobile device or graphics tablet. With touchscreen devices, a user places a stylus on the surface of the screen to draw or make selections by tapping the stylus on the screen. In this manner, the stylus can be used instead of a mouse or trackpad as a pointing device, pen-like input devices which are larger than a stylus, and offer increased functionality such as programmable buttons, pressure sensitivity and electronic erasers, are often known as digital pens. The stylus is the input device for personal digital assistants. It is used on the Nintendo DS and 3DS handheld game consoles, some smartphones, such as Windows Mobile phones, require a stylus for accurate input. Also the stylus is used in the famous Galaxy Note series manufactured by Samsung Electronics, graphics tablets use a stylus containing circuitry, to allow multi-function buttons on the barrel of the pen or stylus to transmit user actions to the tablet. Most tablets detect varying degrees of pressure sensitivity, e. g. for use in a program to vary line thickness or color density. Beyond the side of the mechanism, there has been a need for the physical output of the stylus. The first use of a stylus in a device was the Styalator
40.
Theremin
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The theremin is an early electronic musical instrument controlled without physical contact by the thereminist. It is named after the Westernized name of its Russian inventor, Léon Theremin, the electric signals from the theremin are amplified and sent to a loudspeaker. The theremin was used in soundtracks such as Miklós Rózsas Spellbound, The Lost Weekend. It has also used in theme songs for television shows such as the ITV drama Midsomer Murders. This has led to its association with eerie situations, Theremins are also used in concert music and in popular music genres such as rock. The theremin was originally the product of Soviet government-sponsored research into proximity sensors, the instrument was invented by a young Russian physicist named Lev Sergeyevich Termen in October 1920 after the outbreak of the Russian Civil War. After a lengthy tour of Europe, during which time he demonstrated his invention to packed houses, Theremin moved to the United States, subsequently, Theremin granted commercial production rights to RCA. Although the RCA Thereminvox, was not a success, it fascinated audiences in America. Clara Rockmore, a well-known thereminist, toured to wide acclaim, performing a repertoire in concert halls around the United States. In 1938, Theremin left the United States, though the circumstances related to his departure are in dispute. Many accounts claim he was taken from his New York City apartment by NKVD agents, taken back to the Soviet Union and made to work in a sharashka laboratory prison camp at Magadan, in any case, Theremin did not return to the United States until 1991. However, a niche interest in the theremin persisted, mostly among electronics enthusiasts, one of these electronics enthusiasts, Robert Moog, began building theremins in the 1950s, while he was a high-school student. Moog subsequently published a number of articles about building theremins, Moog credited what he learned from the experience as leading directly to his groundbreaking synthesizer, the Moog. Since the release of the film Theremin, An Electronic Odyssey in 1994, even though many theremin sounds can be approximated on many modern synthesizers, some musicians continue to appreciate the expressiveness, novelty, and uniqueness of using an actual theremin. The film itself has garnered excellent reviews, both theremin instruments and kits are available from manufacturers such as Moog Music Inc. Burns Theremins, Harrison Instruments, Inc. Theremaniacs LLC, PAiA Corporation USA, and Jaycar Electronics, the theremin is distinguished among musical instruments in that it is played without physical contact. The thereminist stands in front of the instrument and moves his or her hands in the proximity of two metal antennas, the distance from one antenna determines frequency, and the distance from the other controls amplitude. Higher notes are played by moving the hand closer to the pitch antenna, louder notes are played by moving the hand away from the volume antenna
41.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
42.
Sensor
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A sensor is always used with other electronics, whether as simple as a light or as complex as a computer. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely used, applications include manufacturing and machinery, airplanes and aerospace, cars, medicine, robotics and many other aspects of our day-to-day life. A sensors sensitivity indicates how much the output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the changes by 1 °C. Some sensors can also affect what they measure, for instance, Sensors are usually designed to have a small effect on what is measured, making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a scale as microsensors using MEMS technology. In most cases, a microsensor reaches a higher speed. Most sensors have a transfer function. The sensitivity is defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is the slope of the transfer function. Converting the sensors electrical output to the measured units requires dividing the output by the slope. In addition, an offset is added or subtracted. For example -40 must be added to the output if 0 V output corresponds to -40 C input, for an analog sensor signal to be processed, or used in digital equipment, it needs to be converted to a digital signal, using an analog-to-digital converter. The full scale range defines the maximum and minimum values of the measured property, the sensitivity may in practice differ from the value specified. This is called a sensitivity error and this is an error in the slope of a linear transfer function. If the output differs from the correct value by a constant. This is an error in the y-intercept of a transfer function. Nonlinearity is deviation of a transfer function from a straight line transfer function
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