1.
Gaseous ionization detectors
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They use the ionising effect of radiation upon a gas-filled sensor. If a particle has enough energy to ionize a gas atom or molecule, gaseous ionisation detectors form an important group of instruments used for radiation detection and measurement. This article gives an overview of the principal types. The accompanying plot shows the variation of ion pair generation with varying applied voltage for constant incident radiation, there are three main practical operating regions, one of which each type utilises. The strength of the field between the electrodes and the type and pressure of the fill gas determines the detectors response to ionizing radiation. Ionization chambers operate at a low electric field strength, selected such that no gas multiplication takes place, the ion current is generated by the creation of ion pairs, consisting of an ion and an electron. The ions drift to the cathode whilst free electrons drift to the anode under the influence of the electric field and this current is independent of the applied voltage if the device is being operated in the ion chamber region. Ion chambers are preferred for high dose rates because they have no dead time. The disadvantages are 1) low output requiring sophisticated electrometer circuit and 2) peration, proportional counters operate at a slightly higher voltage, selected such that discrete avalanches are generated. Each ion pair produces a single avalanche so that a current pulse is generated which is proportional to the energy deposited by the radiation. This is in the proportional counting region, the wire chamber is a multi-electrode form of proportional counter used as a research tool. Geiger-Müller tubes are the components of Geiger counters. This is the Geiger region of operation and this covers all radiation instrument technologies and is useful in selecting the correct gaseous ionisation detector technology for a measurement application. Ionization-type smoke detectors are gaseous ionization detectors in widespread use, a small source of radioactive americium is placed so that it maintains a current between two plates that effectively form an ionisation chamber. If smoke gets between the plates where ionization is taking place, the gas can be neutralized leading to a reduced current. The decrease in current triggers a fire alarm
2.
Ionizing radiation
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Ionizing radiation is radiation that carries enough energy to free electrons from atoms or molecules, thereby ionizing them. Ionizing radiation is made up of energetic particles, ions or atoms moving at high speeds. The boundary between ionizing and non-ionizing electromagnetic radiation that occurs in the ultraviolet is not sharply defined, since different molecules, conventional definition places the boundary at a photon energy between 10 eV and 33 eV in the ultraviolet. Typical ionizing subatomic particles from radioactivity include alpha particles, beta particles, almost all products of radioactive decay are ionizing because the energy of radioactive decay is typically far higher than that required to ionize. Cosmic rays are generated by stars and certain events such as supernova explosions. Cosmic rays may also produce radioisotopes on Earth, which in turn decay, cosmic rays and the decay of radioactive isotopes are the primary sources of natural ionizing radiation on Earth referred to as background radiation. Ionizing radiation can also be generated artificially using X-ray tubes, particle accelerators, ionizing radiation is invisible and not directly detectable by human senses, so radiation detection instruments such as Geiger counters are required to detect it. However, it can cause emission of light upon interaction with matter, such as in Cherenkov radiation. Exposure to ionizing radiation damage to living tissue, and can result in mutation, radiation sickness, cancer. Ionizing radiation is categorized by the nature of the particles or electromagnetic waves that create the ionizing effect and these have different ionization mechanisms, and may be grouped as directly or indirectly ionizing. Any charged massive particle can ionize atoms directly by fundamental interaction through the Coulomb force if it carries sufficient kinetic energy and this includes atomic nuclei, electrons, muons, charged pions, protons, and energetic charged nuclei stripped of their electrons. When moving at relativistic speeds these particles have enough energy to be ionizing. For example, an alpha particle is ionizing, but moves at about 5% c. Natural cosmic rays are made up primarily of protons but also include heavier atomic nuclei like helium ions. Pions can also be produced in large amounts in particle accelerators, alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particle emissions are produced in the process of alpha decay. Alpha particles are named after the first letter in the Greek alphabet, the symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are sometimes written as He2+ or 4 2He2+ indicating a Helium ion with a +2 charge
3.
Electronvolt
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In physics, the electronvolt is a unit of energy equal to approximately 1. 6×10−19 joules. By definition, it is the amount of energy gained by the charge of an electron moving across an electric potential difference of one volt. Thus it is 1 volt multiplied by the elementary charge, therefore, one electronvolt is equal to 6981160217662079999♠1. 6021766208×10−19 J. The electronvolt is not a SI unit, and its definition is empirical, like the elementary charge on which it is based, it is not an independent quantity but is equal to 1 J/C √2hα / μ0c0. It is a unit of energy within physics, widely used in solid state, atomic, nuclear. It is commonly used with the metric prefixes milli-, kilo-, in some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion electronvolts, it is equivalent to the GeV. By mass–energy equivalence, the electronvolt is also a unit of mass and it is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c2, where c is the speed of light in vacuum. It is common to express mass in terms of eV as a unit of mass. The mass equivalent of 1 eV/c2 is 1 eV / c 2 = ⋅1 V2 =1.783 ×10 −36 kg. For example, an electron and a positron, each with a mass of 0.511 MeV/c2, the proton has a mass of 0.938 GeV/c2. In general, the masses of all hadrons are of the order of 1 GeV/c2, the unified atomic mass unit,1 gram divided by Avogadros number, is almost the mass of a hydrogen atom, which is mostly the mass of the proton. To convert to megaelectronvolts, use the formula,1 u =931.4941 MeV/c2 =0.9314941 GeV/c2, in high-energy physics, the electronvolt is often used as a unit of momentum. A potential difference of 1 volt causes an electron to gain an amount of energy and this gives rise to usage of eV as units of momentum, for the energy supplied results in acceleration of the particle. The dimensions of units are LMT−1. The dimensions of units are L2MT−2. Then, dividing the units of energy by a constant that has units of velocity. In the field of particle physics, the fundamental velocity unit is the speed of light in vacuum c. Thus, dividing energy in eV by the speed of light, the fundamental velocity constant c is often dropped from the units of momentum by way of defining units of length such that the value of c is unity
4.
Alpha particle
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Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. They are generally produced in the process of decay. Alpha particles are named after the first letter in the Greek alphabet, the symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are sometimes written as He2+ or 4 2He2+ indicating a helium ion with a +2 charge. If the ion gains electrons from its environment, the particle can be written as a normal helium atom 4 2He. Some science authors may use doubly ionized helium nuclei and alpha particles as interchangeable terms, the nomenclature is not well defined, and thus not all high-velocity helium nuclei are considered by all authors to be alpha particles. As with beta and gamma rays/particles, the used for the particle carries some mild connotations about its production process and energy. Thus, alpha particles may be used as a term when referring to stellar helium nuclei reactions. A higher energy version of alphas than produced in alpha decay is a product of an uncommon nuclear fission result called ternary fission. However, helium nuclei produced by particle accelerators are less likely to be referred to as alpha particles, alpha particles, like helium nuclei, have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have an energy of about 5 MeV. They are a highly ionizing form of radiation, and have low penetration depth. They are able to be stopped by a few centimeters of air, however, so-called long range alpha particles from ternary fission are three times as energetic, and penetrate three times as far. To a lesser extent, this is true of very high-energy helium nuclei produced by particle accelerators. The best-known source of particles is alpha decay of heavier atoms. When an atom emits an alpha particle in alpha decay, the mass number decreases by four due to the loss of the four nucleons in the alpha particle. The atomic number of the atom goes down by two, as a result of the loss of two protons – the atom becomes a new element. Examples of this sort of nuclear transmutation are when uranium becomes thorium, or radium becomes radon gas, alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium, as well as the transuranic elements
5.
Beta particle
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Two forms of beta decay, β− and β+, respectively produce electrons and positrons. Beta particles are a type of ionizing radiation, the neutron turns into a proton through the emission of a virtual W− boson. At the quark level, W− emission turns a down quark into an up quark, the virtual W− boson then decays into an electron and an antineutrino. Beta decay commonly occurs among the neutron-rich fission byproducts produced in nuclear reactors, free neutrons also decay via this process. Both of these contribute to the copious numbers of beta rays. The daughter nucleus is a lower-energy state, of the three common types of radiation given off by radioactive materials, alpha, beta and gamma, beta has the medium penetrating power and the medium ionising power. Although the beta particles given off by different radioactive materials vary in energy, shielding composed of materials with lower atomic weight generates gammas with lower energy, making such shields somewhat more effective per unit mass than ones made of high-Z materials such as lead. Being composed of charged particles, beta radiation is more strongly ionizing than gamma radiation, when passing through matter, a beta particle is decelerated by electromagnetic interactions and may give off bremsstrahlung x-rays. In water, beta radiation from nuclear fission products typically exceeds the speed of light in that material. The intense beta radiation from the rods of pool-type reactors can thus be visualized through the transparent water that covers. The ionizing or excitation effects of particles on matter are the fundamental processes by which radiometric detection instruments detect. The ionization of gas is used in ion chambers and Geiger-Muller counters, beta particles can be used to treat health conditions such as eye and bone cancer and are also used as tracers. Strontium-90 is the material most commonly used to produce beta particles, beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the radiation is absorbed while passing through the product. If the product is too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the paper will then move the rollers to change the thickness of the final product. An illumination device called a betalight contains tritium and a phosphor, as tritium decays, it emits beta particles, these strike the phosphor, causing the phosphor to give off photons, much like the cathode ray tube in a television. Beta-plus decay of a radioactive isotope is the source of the positrons used in positron emission tomography
6.
X-ray
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X-radiation is a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz, X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. Spelling of X-ray in the English language includes the variants x-ray, xray, X-rays with high photon energies are called hard X-rays, while those with lower energy are called soft X-rays. Due to their ability, hard X-rays are widely used to image the inside of objects, e. g. in medical radiography. The term X-ray is metonymically used to refer to an image produced using this method. Since the wavelengths of hard X-rays are similar to the size of atoms they are useful for determining crystal structures by X-ray crystallography. By contrast, soft X-rays are easily absorbed in air, the length of 600 eV X-rays in water is less than 1 micrometer. There is no consensus for a definition distinguishing between X-rays and gamma rays, one common practice is to distinguish between the two types of radiation based on their source, X-rays are emitted by electrons, while gamma rays are emitted by the atomic nucleus. This definition has problems, other processes also can generate these high-energy photons. One common alternative is to distinguish X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m and this criterion assigns a photon to an unambiguous category, but is only possible if wavelength is known. Occasionally, one term or the other is used in specific contexts due to precedent, based on measurement technique. Thus, gamma-rays generated for medical and industrial uses, for radiotherapy, in the ranges of 6–20 MeV. X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds and this makes it a type of ionizing radiation, and therefore harmful to living tissue. A very high radiation dose over a period of time causes radiation sickness. In medical imaging this increased risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy, hard X-rays can traverse relatively thick objects without being much absorbed or scattered. For this reason, X-rays are widely used to image the inside of visually opaque objects, the most often seen applications are in medical radiography and airport security scanners, but similar techniques are also important in industry and research
7.
Absorbed dose
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Absorbed dose is a physical dose quantity D representing the mean energy imparted to matter per unit mass by ionizing radiation. In the SI system of units, the unit of measure is joules per kilogram, the non-SI CGS unit rad is sometimes also used, predominantly in the USA. Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection and radiology and it is also used to directly compare the effect of radiation on inanimate matter. The quantity absorbed dose is of importance in radiological protection for calculating radiation dose. However, absorbed dose is a quantity and used unmodified is not an adequate indicator of the likely health effects in humans. It has been found that for stochastic radiation risk consideration must be given to the type of radiation and the sensitivity of the irradiated tissues, which requires the use of modifying factors. Conventionally therefore, unmodified absorbed dose is not used for comparing stochastic risks, to represent stochastic risk the equivalent dose H T and effective dose E are used, and appropriate dose factors and coefficients are used to calculate these from the absorbed dose. Equivalent and effective dose quantities are expressed in units of the sievert or rem which implies that biological effects have been taken into account and these are usually in accordance with the recommendations of the International Committee on Radiation Protection and International Commission on Radiation Units and Measurements. The coherent system of protection quantities developed by them is shown in the accompanying diagram. Absorbed dose is used to rate the survivability of devices such as components in ionizing radiation environments. Absorbed dose is the physical quantity used to ensure irradiated food has received the correct dose to ensure effectiveness. Variable doses are used depending on the application and can be as high as 70 kGy, the absorbed dose is equal to the radiation exposure of the radiation beam multiplied by the ionization energy of the medium to be ionized. For example, the energy of dry air at 20 °C and 101.325 kPa of pressure is 33. 97±0.06 J/C. Therefore, an exposure of 2. 58×10−4 C/kg would deposit an absorbed dose of 8. 76×10−3 J/kg in dry air at those conditions, self-shielding means that the absorbed dose will be higher in the tissues facing the source than deeper in the body. The mass average can be important in evaluating the risks of radiotherapy treatments, since they are designed to very specific volumes in the body. For example, if 10% of a bone marrow mass is irradiated with 10 Gy of radiation locally. Bone marrow makes up 4% of the mass, so the whole-body absorbed dose would be 0.04 Gy. The first figure is indicative of the effects on the tumour, while the second
8.
Ionization chamber
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Ion chambers have a good uniform response to radiation over a wide range of energies and are the preferred means of measuring high levels of gamma radiation. They are widely used in the power industry, research labs, radiography, radiobiology. An ionization chamber measures the charge from the number of ion pairs created within a gas caused by incident radiation and it consists of a gas-filled chamber with two electrodes, known as anode and cathode. The electrodes may be in the form of plates, or a cylinder arrangement with a coaxially located internal anode wire. A voltage potential is applied between the electrodes to create a field in the fill gas. This generates a current which is measured by an electrometer circuit. The electrometer must be capable of measuring the small output current which is in the region of femtoamperes to picoamperes, depending on the chamber design, radiation dose. This continual generation of charge produces a current, which is a measure of the total ionizing dose entering the chamber. However, the chamber cannot discriminate between radiation types and cannot produce a spectrum of radiation. This is in distinction to the Geiger-Müller tube or the proportional counter whereby secondary electrons, the following chamber types are commonly used. This is a chamber open to atmosphere, where the fill gas is ambient air. The domestic smoke detector is an example of this, where a natural flow of air through the chamber is necessary so that smoke particles can be detected by the change in ion current. Other examples are applications where the ions are created outside the chamber but are carried in by a flow of air or gas. These chambers are normally cylindrical and operate at atmospheric pressure, and this is to stop moisture building up in the interior of the chamber, which would otherwise be introduced by the pump effect of changing atmospheric air pressure. These chambers have a body made of aluminium or plastic a few millimetres thick. The material is selected to have a number similar to that of air so that the wall is said to be air equivalent over a range of radiation beam energies. The higher the number of the wall material, the greater the chance of interaction. The wall thickness is a trade-off between maintaining the air effect with a wall, and increasing sensitivity by using a thinner wall
9.
Townsend discharge
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Those electrons are in turn accelerated and free additional electrons. The result is a multiplication that permits electrical conduction through the gas. The discharge requires a source of electrons and a significant electric field. The Townsend discharge is named after John Sealy Townsend, who discovered the fundamental ionisation mechanism by his work between 1897 and 1901, the avalanche occurs in a gaseous medium that can be ionised. The electric field and the mean path of the electron must allow free electrons to acquire an energy level that can cause impact ionisation. If the electric field is too small, then the electrons do not acquire enough energy, if the mean free path is too short, the electron gives up its acquired energy in a series of non-ionising collisions. If the mean free path is too long, then the electron reaches the anode before colliding with another molecule, the avalanche mechanism is shown in the accompanying diagram. The electric field is applied across a gaseous medium, initial ions are created with ionising radiation, an original ionisation event produces an ion pair, the positive ion accelerates towards the cathode while the free electron accelerates towards the anode. If the electric field is strong enough, the electron can gain sufficient velocity to liberate another electron when it next collides with a molecule. The two free electrons then travel towards the anode and gain sufficient energy from the field to cause further impact ionisations. This process is effectively a chain reaction that generates free electrons, the total number of electrons reaching the anode is equal to the number of collisions, plus the single initiating free electron. Initially, the number of collisions grows exponentially, the limit to the multiplication in an electron avalanche is known as the Raether limit. The Townsend avalanche can have a range of current densities. In common gas-filled tubes, such as used as gaseous ionisation detectors. Townsends early experimental apparatus consisted of parallel plates forming two sides of a chamber filled with a gas. A direct current high-voltage source was connected between the plates, the lower voltage plate being the cathode while the other was the anode, Townsend observed currents varying exponentially over ten or more orders of magnitude with a constant applied voltage when the distance between the plates was varied. He also discovered that gas pressure influenced conduction, he was able to generate ions in gases at low pressure with a lower voltage than that required to generate a spark. This observation overturned conventional thinking about the amount of current that a gas could conduct
10.
Spectroscopy
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Spectroscopy /spɛkˈtrɒskəpi/ is the study of the interaction between matter and electromagnetic radiation. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency. Spectroscopic data is represented by an emission spectrum, a plot of the response of interest as a function of wavelength or frequency. Spectroscopy and spectrography are terms used to refer to the measurement of radiation intensity as a function of wavelength and are used to describe experimental spectroscopic methods. Spectral measurement devices are referred to as spectrometers, spectrophotometers, spectrographs or spectral analyzers, daily observations of color can be related to spectroscopy. Neon lighting is an application of atomic spectroscopy. Neon and other noble gases have characteristic emission frequencies, neon lamps use collision of electrons with the gas to excite these emissions. Inks, dyes and paints include chemical compounds selected for their characteristics in order to generate specific colors. A commonly encountered molecular spectrum is that of nitrogen dioxide, gaseous nitrogen dioxide has a characteristic red absorption feature, and this gives air polluted with nitrogen dioxide a reddish-brown color. Rayleigh scattering is a spectroscopic scattering phenomenon that accounts for the color of the sky, Spectroscopy is used in physical and analytical chemistry because atoms and molecules have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms, Spectroscopy is also used in astronomy and remote sensing on earth. The measured spectra are used to determine the composition and physical properties of astronomical objects. One of the concepts in spectroscopy is a resonance and its corresponding resonant frequency. Resonances were first characterized in mechanical systems such as pendulums, mechanical systems that vibrate or oscillate will experience large amplitude oscillations when they are driven at their resonant frequency. A plot of amplitude vs. excitation frequency will have a peak centered at the resonance frequency and this plot is one type of spectrum, with the peak often referred to as a spectral line, and most spectral lines have a similar appearance. In quantum mechanical systems, the resonance is a coupling of two quantum mechanical stationary states of one system, such as an atom, via an oscillatory source of energy such as a photon. The coupling of the two states is strongest when the energy of the matches the energy difference between the two states. The energy of a photon is related to its frequency by E = h ν where h is Plancks constant, spectra of atoms and molecules often consist of a series of spectral lines, each one representing a resonance between two different quantum states
11.
Integral
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In mathematics, an integral assigns numbers to functions in a way that can describe displacement, area, volume, and other concepts that arise by combining infinitesimal data. Integration is one of the two operations of calculus, with its inverse, differentiation, being the other. The area above the x-axis adds to the total and that below the x-axis subtracts from the total, roughly speaking, the operation of integration is the reverse of differentiation. For this reason, the integral may also refer to the related notion of the antiderivative. In this case, it is called an integral and is written. The integrals discussed in this article are those termed definite integrals, a rigorous mathematical definition of the integral was given by Bernhard Riemann. It is based on a procedure which approximates the area of a curvilinear region by breaking the region into thin vertical slabs. A line integral is defined for functions of two or three variables, and the interval of integration is replaced by a curve connecting two points on the plane or in the space. In a surface integral, the curve is replaced by a piece of a surface in the three-dimensional space and this method was further developed and employed by Archimedes in the 3rd century BC and used to calculate areas for parabolas and an approximation to the area of a circle. A similar method was developed in China around the 3rd century AD by Liu Hui. This method was used in the 5th century by Chinese father-and-son mathematicians Zu Chongzhi. The next significant advances in integral calculus did not begin to appear until the 17th century, further steps were made in the early 17th century by Barrow and Torricelli, who provided the first hints of a connection between integration and differentiation. Barrow provided the first proof of the theorem of calculus. Wallis generalized Cavalieris method, computing integrals of x to a power, including negative powers. The major advance in integration came in the 17th century with the independent discovery of the theorem of calculus by Newton. The theorem demonstrates a connection between integration and differentiation and this connection, combined with the comparative ease of differentiation, can be exploited to calculate integrals. In particular, the theorem of calculus allows one to solve a much broader class of problems. Equal in importance is the mathematical framework that both Newton and Leibniz developed
12.
Electric current
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An electric current is a flow of electric charge. In electric circuits this charge is carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas. The SI unit for measuring a current is the ampere. Electric current is measured using a device called an ammeter, electric currents cause Joule heating, which creates light in incandescent light bulbs. They also create magnetic fields, which are used in motors, inductors and generators, the particles that carry the charge in an electric current are called charge carriers. In metals, one or more electrons from each atom are loosely bound to the atom and these conduction electrons are the charge carriers in metal conductors. The conventional symbol for current is I, which originates from the French phrase intensité de courant, current intensity is often referred to simply as current. The I symbol was used by André-Marie Ampère, after whom the unit of current is named, in formulating the eponymous Ampères force law. The notation travelled from France to Great Britain, where it became standard, in a conductive material, the moving charged particles which constitute the electric current are called charge carriers. In other materials, notably the semiconductors, the carriers can be positive or negative. Positive and negative charge carriers may even be present at the same time, a flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction. Since current can be the flow of positive or negative charges. The direction of current is arbitrarily defined as the same direction as positive charges flow. This is called the direction of current I. If the current flows in the direction, the variable I has a negative value. When analyzing electrical circuits, the direction of current through a specific circuit element is usually unknown. Consequently, the directions of currents are often assigned arbitrarily
13.
Kinetic energy
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In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes, the same amount of work is done by the body in decelerating from its current speed to a state of rest. In classical mechanics, the energy of a non-rotating object of mass m traveling at a speed v is 12 m v 2. In relativistic mechanics, this is an approximation only when v is much less than the speed of light. The standard unit of energy is the joule. The adjective kinetic has its roots in the Greek word κίνησις kinesis, the dichotomy between kinetic energy and potential energy can be traced back to Aristotles concepts of actuality and potentiality. The principle in classical mechanics that E ∝ mv2 was first developed by Gottfried Leibniz and Johann Bernoulli, Willem s Gravesande of the Netherlands provided experimental evidence of this relationship. By dropping weights from different heights into a block of clay, Émilie du Châtelet recognized the implications of the experiment and published an explanation. The terms kinetic energy and work in their present scientific meanings date back to the mid-19th century, early understandings of these ideas can be attributed to Gaspard-Gustave Coriolis, who in 1829 published the paper titled Du Calcul de lEffet des Machines outlining the mathematics of kinetic energy. William Thomson, later Lord Kelvin, is given the credit for coining the term kinetic energy c, energy occurs in many forms, including chemical energy, thermal energy, electromagnetic radiation, gravitational energy, electric energy, elastic energy, nuclear energy, and rest energy. These can be categorized in two classes, potential energy and kinetic energy. Kinetic energy is the movement energy of an object, Kinetic energy can be transferred between objects and transformed into other kinds of energy. Kinetic energy may be best understood by examples that demonstrate how it is transformed to, for example, a cyclist uses chemical energy provided by food to accelerate a bicycle to a chosen speed. On a level surface, this speed can be maintained without further work, except to overcome air resistance, the chemical energy has been converted into kinetic energy, the energy of motion, but the process is not completely efficient and produces heat within the cyclist. The kinetic energy in the moving cyclist and the bicycle can be converted to other forms, for example, the cyclist could encounter a hill just high enough to coast up, so that the bicycle comes to a complete halt at the top. The kinetic energy has now largely converted to gravitational potential energy that can be released by freewheeling down the other side of the hill. Since the bicycle lost some of its energy to friction, it never regains all of its speed without additional pedaling, the energy is not destroyed, it has only been converted to another form by friction
14.
Photon
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A photon is an elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force. The photon has zero rest mass and is moving at the speed of light. Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles. For example, a photon may be refracted by a lens and exhibit wave interference with itself. The quanta in a light wave cannot be spatially localized, some defined physical parameters of a photon are listed. The modern concept of the photon was developed gradually by Albert Einstein in the early 20th century to explain experimental observations that did not fit the classical model of light. The benefit of the model was that it accounted for the frequency dependence of lights energy. The photon model accounted for observations, including the properties of black-body radiation. In that model, light was described by Maxwells equations, in 1926 the optical physicist Frithiof Wolfers and the chemist Gilbert N. Lewis coined the name photon for these particles. After Arthur H. Compton won the Nobel Prize in 1927 for his studies, most scientists accepted that light quanta have an independent existence. In the Standard Model of particle physics, photons and other particles are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of particles, such as charge, mass and it has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Recently, photons have been studied as elements of quantum computers, in 1900, the German physicist Max Planck was studying black-body radiation and suggested that the energy carried by electromagnetic waves could only be released in packets of energy. In his 1901 article in Annalen der Physik he called these packets energy elements, the word quanta was used before 1900 to mean particles or amounts of different quantities, including electricity. In 1905, Albert Einstein suggested that waves could only exist as discrete wave-packets. He called such a wave-packet the light quantum, the name photon derives from the Greek word for light, φῶς. Arthur Compton used photon in 1928, referring to Gilbert N. Lewis, the name was suggested initially as a unit related to the illumination of the eye and the resulting sensation of light and was used later in a physiological context. Although Wolferss and Lewiss theories were contradicted by many experiments and never accepted, in physics, a photon is usually denoted by the symbol γ
15.
Gamma ray
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Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon
16.
Radioactive contamination
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Such contamination presents a hazard because of the radioactive decay of the contaminants, which emit harmful ionising radiation such as alpha particles or beta particles, gamma rays or neutrons. It is important to be clear that the contamination gives rise to the hazard. Contamination may affect a person, a place, an animal, a spilled vial of radioactive material like uranyl nitrate may contaminate the floor and any rags used to wipe up the spill. Radioactive contamination is typically the result of a spill or accident during the production, or use of, radionuclides, less typically, nuclear fallout is the distribution of radioactive contamination by a nuclear explosion. The amount of material released in an accident is called the source term. Contamination may occur from radioactive gases, liquids or particles, for example, if a radionuclide used in nuclear medicine is spilled, the material could be spread by people as they walk around. Radioactive contamination may also be a result of certain processes. In cases that radioactive material cannot be contained, it may be diluted to safe concentrations, for a discussion of environmental contamination by alpha emitters please see actinides in the environment. Contamination does not include residual radioactive material remaining at a site after the completion of decommissioning, therefore, radioactive material in sealed and designated containers is not properly referred to as contamination, although the units of measurement might be the same. Containment is the way of preventing contamination being released into the environment or coming into contact or being ingested by humans. Being within the intended Containment differentiates radioactive material from radioactive contamination, when radioactive materials are concentrated to a detectable level outside a containment, the area affected is generally referred to as contaminated. There are a number of techniques for containing radioactive material so that it does not spread beyond the containment. In the case of liquids this is by the use of high integrity tanks or containers, where material is likely to become airborne, then extensive use is made of the glovebox, which is a common technique in hazardous laboratory and process operations in many industries. A variety of radionuclides occur naturally in the environment, elements like uranium and thorium, and their decay products, are present in rock and soil. Potassium-40, a nuclide, makes up a small percentage of all potassium and is present in the human body. Other nuclides, like carbon-14, which is present in all living organisms, are created by cosmic rays. These levels of radioactivity pose little danger but can confuse measurement, a particular problem is encountered with naturally generated radon gas which can affect instruments which are set to detect contamination close to normal background levels and can cause false alarms. Because of this skill is required by the operator of radiological survey equipment to differentiate between background radiation and the radiation emanates from contamination
17.
Stopping power (particle radiation)
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Its application is important in areas such as radiation protection and nuclear medicine. Both charged and uncharged particles lose energy while passing through matter, positive ions are considered in most cases below. The stopping power depends on the type and energy of the radiation and on the properties of the material it passes, since the production of an ion pair requires a fixed amount of energy, the density of ionization is proportional to the stopping power. The stopping power of the material is numerically equal to the loss of energy E per unit path length, the force usually increases toward the end of range and reaches a maximum, the Bragg peak, shortly before the energy drops to zero. The curve that describes the force as function of the depth is called the Bragg curve. This is of practical importance for radiation therapy. The equation above defines the linear stopping power which in the system is expressed in N but is usually indicated in other units like MeV/mm or similar. If a substance is compared in gaseous and solid form, then the linear stopping powers of the two states are very different just because of the different density, the mass stopping power then depends only very little on the density of the material. The picture shows how the power of 5.49 MeV alpha particles increases while the particle traverses air. This particular energy corresponds to that of the alpha radiation from naturally radioactive gas radon which is present in the air in minute amounts. The deposited energy can be obtained by integrating the stopping power over the path length of the ion while it moves in the material. Electronic stopping refers to the slowing down of a projectile ion due to the collisions between bound electrons in the medium and the ion moving through it. The term inelastic is used to signify that energy is lost during the process, linear electronic stopping power is identical to unrestricted linear energy transfer. Instead of energy transfer, some consider the electronic stopping power as momentum transfer between electron gas and energetic ion. This is consistent with the result of Bethe in the energy range. Instead, the stopping power is often given as a simple function of energy F e which is an average taken over all energy loss processes for different charge states. It can be determined to an accuracy of a few % in the energy range above several hundred keV per nucleon from theoretical treatments. At energies lower than about 100 keV per nucleon, it more difficult to determine the electronic stopping theoretically
18.
United Kingdom
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The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or Britain, is a sovereign country in western Europe. Lying off the north-western coast of the European mainland, the United Kingdom includes the island of Great Britain, Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. The Irish Sea lies between Great Britain and Ireland, with an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world and the 11th-largest in Europe. It is also the 21st-most populous country, with an estimated 65.1 million inhabitants, together, this makes it the fourth-most densely populated country in the European Union. The United Kingdom is a monarchy with a parliamentary system of governance. The monarch is Queen Elizabeth II, who has reigned since 6 February 1952, other major urban areas in the United Kingdom include the regions of Birmingham, Leeds, Glasgow, Liverpool and Manchester. The United Kingdom consists of four countries—England, Scotland, Wales, the last three have devolved administrations, each with varying powers, based in their capitals, Edinburgh, Cardiff and Belfast, respectively. The relationships among the countries of the UK have changed over time, Wales was annexed by the Kingdom of England under the Laws in Wales Acts 1535 and 1542. A treaty between England and Scotland resulted in 1707 in a unified Kingdom of Great Britain, which merged in 1801 with the Kingdom of Ireland to form the United Kingdom of Great Britain and Ireland. Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain, there are fourteen British Overseas Territories. These are the remnants of the British Empire which, at its height in the 1920s, British influence can be observed in the language, culture and legal systems of many of its former colonies. The United Kingdom is a country and has the worlds fifth-largest economy by nominal GDP. The UK is considered to have an economy and is categorised as very high in the Human Development Index. It was the worlds first industrialised country and the worlds foremost power during the 19th, the UK remains a great power with considerable economic, cultural, military, scientific and political influence internationally. It is a nuclear weapons state and its military expenditure ranks fourth or fifth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946 and it has been a leading member state of the EU and its predecessor, the European Economic Community, since 1973. However, on 23 June 2016, a referendum on the UKs membership of the EU resulted in a decision to leave. The Acts of Union 1800 united the Kingdom of Great Britain, Scotland, Wales and Northern Ireland have devolved self-government
19.
Health and Safety Executive
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The Health and Safety Executive is a non-departmental public body of the United Kingdom with its headquarters in Liverpool, England. It is the responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare. Responsibility in Northern Ireland lies with the Health and Safety Executive for Northern Ireland, the HSE was created by the Health and Safety at Work etc. The HSE is sponsored by the Department for Work and Pensions, as part of its work HSE investigates industrial accidents, small and large, including major incidents such as the explosion and fire at Buncefield in 2005. Though it formerly reported to the Health and Safety Commission, on 1 April 2008, the Executives duties are to, Assist and encourage persons concerned with matters relevant to the operation of the objectives of the Health and Safety at Work etc. Make arrangements for and encourage research and publication, training and information in connection with its work. The Executive is further obliged to keep the Secretary of State informed of its plans and ensure alignment with the policies of the Secretary of State, the Secretary of State can give directions to the Executive. On 1 April 2006, the Executive ceased to have responsibility for railway safety, the Executive is responsible for the Employment Medical Advisory Service, which operates as part of its Field Operations Directorate. Local authorities are responsible for the enforcement of health and safety legislation in shops, offices and it was established in 1921 under the Safety in Mines Research Board to carry out large-scale tests related to mining hazards. In 1995 the HSL was formed, including the Buxton site, in 2004 the Sheffield activities moved to Buxton, and the University of Sheffield took over the Sheffield laboratory site. It now operates as an agency carrying out research and investigations for the HSE, other government agencies. HM Inspectorate of Mines is responsible for the implementation and inspection of safe working procedures within all UK mine workings. It is based in Sheffield, South Yorkshire, the Offshore Safety Division was established as a division within HSE in April 1991. This was in response to recommendations of the Cullen Inquiry into the Piper Alpha disaster on 6 July 1988, at the time of the disaster the Department of Energy was responsible for both production and offshore safety, this was perceived as entailing a conflict of interests. Dr Tony Barrell, Director of HSE’s Technology and Air Pollution Division was appointed Chief Executive of OSD, at the same time Ministerial oversight was transferred from the DEn to the Department of Employment. The Offshore Safety Act 1992 made the Mineral Workings Act 1971 and its subsidiary Regulations relevant statutory provisions of the Health and Safety at work etc, Act 1974. The OSD’s initial responsibilities included the establishment of the Safety Case Regulations, a review of existing safety legislation. OSD became part of the HSE’s new Hazardous Installations Directorate in 1999, the HSE currently administrates the Occupational Safety & Health Consultants Register, a central register of registered safety consultants within the United Kingdom and Northern Ireland
20.
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
21.
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
22.
Geophone
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A geophone is a device that converts ground movement into voltage, which may be recorded at a recording station. The deviation of this voltage from the base line is called the seismic response and is analyzed for structure of the earth. The term geophone derives from the Greek word γῆ meaning earth, geophones have historically been passive analog devices and typically comprise a spring-mounted magnetic mass moving within a wire coil to generate an electrical signal. The response of a geophone is proportional to ground velocity. MEMS have a higher noise level than geophones and can only be used in strong motion or active seismic applications. The frequency response of a geophone is that of an oscillator, fully determined by corner frequency. Since the corner frequency is proportional to the root of the moving mass. It is possible to lower the corner electronically, at the price of higher noise. Although waves passing through the earth have a nature, geophones are normally constrained to respond to single dimension - usually the vertical. However, some require the full wave to be used. In analog devices, three moving coil elements are mounted in an arrangement within a single case. The majority of geophones are used in seismology to record the energy waves reflected by the subsurface geology. In this case the primary interest is in the motion of the Earths surface. However, not all the waves are upwards travelling, a strong, horizontally transmitted wave known as ground-roll also generates vertical motion that can obliterate the weaker vertical signals. By using large areal arrays tuned to the wavelength of the ground-roll the dominant noise signals can be attenuated, analog geophones are very sensitive devices which can respond to very distant tremors. These small signals can be drowned by larger signals from local sources and it is possible though to recover the small signals caused by large but distant events by correlating signals from several geophones deployed in an array. Signals which are registered only at one or few geophones can be attributed to unwanted, local events and it can be assumed that small signals that register uniformly at all geophones in an array can be attributed to a distant and therefore significant event. The sensitivity of passive geophones is typically 30 Volts/, so they are in general not a replacement for broadband seismometers, conversely, some applications of geophones are interested only in very local events
23.
Hydrophone
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A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change, such piezoelectric materials, or transducers, can convert a sound signal into an electrical signal since sound is a pressure wave. Some transducers can also serve as a projector, but not all have this capability, a hydrophone can listen to sound in air but will be less sensitive due to its design as having a good acoustic impedance match to water, which is a denser fluid than air. The earliest widely used design was the Fessenden oscillator, an electrodynamically driven clamped-edge circular plate transducer operating at 500,1000, ernest Rutherford, in England, led pioneer research in hydrophones using piezoelectric devices, and his only patent was for a hydrophone device. The acoustic impedance of piezoelectric materials facilitated their use as underwater transducers, the piezoelectric hydrophone was used late in World War I, by convoy escorts detecting U-boats, greatly impacting the effectiveness of submarines. From late in World War I until the introduction of active sonar, hydrophones were the method for submarines to detect targets while submerged. A small single cylindrical ceramic transducer can achieve near perfect omnidirectional reception and this type of hydrophone can be produced from a low-cost omnidirectional type, but must be used while stationary, as the reflector impedes its movement through water. A new way to direct is to use a body around the hydrophone. The array may be steered using a beamformer, most commonly, hydrophones are arranged in a line array but may be in two- or three-dimensional arrangements. These are capable of clearly recording extremely low frequency infrasound, including many unexplained ocean sounds, communication with submarines Underwater acoustics Sonar Reflection seismology Pike, John. How to build & use low-cost hydrophones, dOSITS—Hydrophone introduction at Discovery of Sound in the Sea orcasound. High Quality Hydrophones— High quality manufacturer of Hydrophones
24.
Microphone
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A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal. Several different types of microphone are in use, which employ different methods to convert the air pressure variations of a wave to an electrical signal. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced, in order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones, some of the first examples, from fifth century BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheatres. In 1665, the English physicist Robert Hooke was the first to experiment with an other than air with the invention of the lovers telephone made of stretched wire with a cup attached at each end. German inventor Johann Philipp Reis designed an early sound transmitter that used a strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the transmitter design in Scottish-American Alexander Graham Bells telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a poor sound quality. The first microphone that enabled proper voice telephony was the carbon microphone and this was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, the carbon microphone is the direct prototype of todays microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886 and this microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910. In 1916, E. C. Wente of Western Electric developed the next breakthrough with the first condenser microphone, in 1923, the first practical moving coil microphone was built. The Marconi Skykes or magnetophon, developed by Captain H. J. Round, was the standard for BBC studios in London and this was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the microphone was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson. Over the years these microphones were developed by companies, most notably RCA that made large advancements in pattern control. With television and film technology booming there was demand for high fidelity microphones, electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. During the second half of 20th century development advanced quickly with the Shure Brothers bringing out the SM58, digital was pioneered by Milab in 1999 with the DM-1001. The latest research developments include the use of optics, lasers and interferometers
25.
Seismometer
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Seismometers are instruments that measure motion of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, the seismometer was invented by the Chinese polymath Zhang Heng in AD132 during the Han dynasty. The first Western description of a comes from the French physicist and priest Jean de Hautefeuille in 1703. The modern seismometer was developed in the 19th century by John Milne, James Alfred Ewing, seismograph is another Greek term from seismós and γράφω, gráphō, to draw. The concerning technical discipline is called seismometry, a branch of seismology, a simple seismometer that is sensitive to up-down motions of the earth can be understood by visualizing a weight hanging on a spring. The spring and weight are suspended from a frame that moves along with the earthʼs surface, as the earth moves, the relative motion between the weight and the earth provides a measure of the vertical ground motion. Any movement of the moves the frame. The mass tends not to move because of its inertia, early seismometers used optical levers or mechanical linkages to amplify the small motions involved, recording on soot-covered paper or photographic paper. In some systems, the mass is held nearly motionless relative to the frame by a negative feedback loop. The motion of the relative to the frame is measured. The voltage needed to produce this force is the output of the seismometer, in other systems the weight is allowed to move, and its motion produces a voltage in a coil attached to the mass and moving through the magnetic field of a magnet attached to the frame. This design is used in the geophones used in seismic surveys for oil. Professional seismic observatories usually have instruments measuring three axes, north-south, east-west, and the vertical, if only one axis is measured, this is usually the vertical because it is less noisy and gives better records of some seismic waves. The foundation of a station is critical. A professional station is mounted on bedrock. The best mountings may be in deep boreholes, which avoid thermal effects, ground noise and tilting from weather, other instruments are often mounted in insulated enclosures on small buried piers of unreinforced concrete. Reinforcing rods and aggregates would distort the pier as the temperature changes, a site is always surveyed for ground noise with a temporary installation before pouring the pier and laying conduit. Originally, European seismographs were placed in an area after a destructive earthquake
26.
Blind spot monitor
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The blind spot monitor is a vehicle-based sensor device that detects other vehicles located to the driver’s side and rear. Warnings can be visual, audible, vibrating, or tactile, however, blind spot monitors are an option that may do more than monitor the sides and rear of the vehicle. They may also include Cross Traffic Alert, which alerts drivers backing out of a parking space when traffic is approaching from the sides, if side view mirrors are properly adjusted on a car, there is no blind spot on the sides. Platzer received a patent for his blind spot monitor, and it has incorporated into various products associated with Ford Motor Company. The blind zone mirror has been touted as an elegant and relatively inexpensive solution to this recognized problem, Volvo BLIS is an acronym for Blind Spot Information System, a system of protection developed by Volvo. Volvos previous parent, Ford Motor Company, has adapted the system to its Ford, Lincoln. Mazda Mazda was the first Japanese automaker to offer a blind spot monitor and it was initially introduced on the 2008 Mazda CX-9 Grand Touring and remained limited to only that highest trim level through the 2012 model year. For 2013, BSM was standard on both the CX-9 Touring and Grand Touring models, Mazda also added BSM to the redesigned 2009 Mazda 6. Blind spot monitoring was standard equipment on the 6i and 6s Grand Touring trim levels, and was an available option on some lower trim levels. Mazda has since expanded the availability of BSM, having added it to the feature list of the Mazda3, CX-5, MX-5 Miata, Ford Ford uses the acronym BLIS for its blind spot detection. The system is both in drive and neutral transmission gears, and is turned off when in reverse or park gears. On Ford products, the system was first introduced in the spring of 2009, on the 2010 Ford Fusion and Fusion Hybrid,2010 Mercury Milan and Milan Hybrid, Mitsubishi Mitsubishi offers a Blind Spot Warning on the Pajero Sport launched in 2016. Toyota Toyota Motors Safety Sense package, which includes Blind Spot Monitoring, among other features, is standard equipment in multiple models sold in the U. S, in 2010, the Nissan Fuga/Infiniti M for the first time offered counter steering capabilities to keep the vehicle from colliding. Those capabilities have been adopted by competitors, such as Toyota, youTube Ford How-to video, BLIS with Cross-Traffic Alert Google patent search of Blind spot monitoring system The danger of blind zones The area behind your vehicle can be a killing zone
27.
Crankshaft position sensor
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A crank sensor is an electronic device used in an internal combustion engine, both petrol and diesel, to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control the fuel injection or the ignition system timing, before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on petrol engines. This method is used to synchronise a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also used as the primary source for the measurement of engine speed in revolutions per minute. Common mounting locations include the main crank pulley, the flywheel and this sensor is the 2nd most important sensor in modern-day engines after the camshaft position sensor. When it fails, there is a probability the engine will not start, there are three main types of sensor commonly in use. The Hall Effect sensor, Optical sensor or the Inductive sensor, some engines, such as GMs Premium V family, use crank position sensors which read a reluctor ring integral to the harmonic balancer. This is a more accurate method of determining the position of the crankshaft. The functional objective for the position sensor is to determine the position and/or rotational speed of the crank. Engine Control Units use the information transmitted by the sensor to control such as ignition timing. In a diesel the sensor will control the fuel injection, the sensor output may also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four stroke engine. Sometimes, the sensor may become burnt or worn out - or just die of old age at high mileage, one likely cause of crankshaft position sensor failure is exposure to extreme heat. Others are vibration causing a wire to fracture or corrosion on the pins of harness connectors, many modern crankshaft sensors are sealed units and therefore will not be damaged by water or other fluids. When it goes wrong, it stops transmitting the signal contains the vital data for the ignition. A bad crank position sensor can worsen the way the engine idles, if the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires. Acceleration might be hesitant, and abnormal shaking during engine idle might occur, in the worst case the car may not start. The first sign of crankshaft failure, usually, is the refusal of the engine to start when hot. Another type of sensor is used on bicycles to monitor the position of the crankset
28.
Curb feeler
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Curb feelers or curb finders are springs or wires installed on a vehicle which act as whiskers to alert drivers when they are at the right distance from the curb while parking. The devices are fitted low on the body, close to the wheels, as the vehicle approaches the curb, the protruding feelers scrape against the curb, making a noise and alerting the driver in time to avoid damaging the wheels or hubcaps. The feelers are manufactured to be flexible and do not easily break, curb feelers are still used on some hot rods when a 1950s look is wanted. They are especially popular for cars with tires, which easily lose their white coating when scraped against the curb. Sometimes curb feelers are found only on the side of the car. Sometimes they are added next to the front wheels. Some curb feelers have a wire or spring, while others have two to increase the area that can be protected. Any particular car may have just one curb feeler installed or more if attached near the front and rear, as well as on both sides of the vehicle. Buses are sometimes fitted with curb feelers, which can assist the driver in ensuring that the bus is close enough to the curb to allow passengers to step to and from the curb easily. This will give a warning nudge to anyone in the danger area, the belting is stiff enough to hold its shape but flexible enough to give if it runs into a miner or vice versa. The flexibility also allows this curb feeler to drag against the rib or be smacked by a car with little or no damage. A little spray from a can of paint will make the belt a visual warning device as well. One or two on each corner will help or put as many as you want, curb feelers based on optical technology are designed to function the same way but work in the proximity of an obstruction rather than having to come into physical contact with it. As described by one United States patent, An electronic curb feeler system uses two pairs of optical sensor units to detect an object located near the front end of a vehicle during parking. Devices such as this, and simpler electronic devices similar to the original wire curb feelers used on cars, are used in the design of various mobile robotic devices, one robotics company that does work for the United States Department of Defense uses laser-assisted curb feeler technology
29.
Defect detector
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A defect detector is a device used on railroads to detect axle and signal problems in passing trains. The detectors are normally integrated into the tracks and often include sensors to detect different kinds of problems that could occur. The use of defect detectors has since spread to other overseas railroads, to detect hotboxes, i. e. overheating bearings, they would look for oil smoke during the day or a red glow at night. As early as the 1940s, automatic defect detectors were installed to improve upon the manual process, the detectors would transmit their data via wired links to remote read-outs in stations, offices or interlocking towers. A stylus-and-cylinder gauge would record a reading for every axle, if a journal were too hot, or if some other defect were detected, early line-side defect detectors were typically housed in concrete bungalows, roughly every 10–20 miles. The crew stationed at the rear of the train would observe this light and, if a defect were indicated, the first computerized detectors used fixed-display boards. These had a numeric display and a number of indicator lights relating to the nature of defects. A number would be displayed in lights on the board after the train had cleared the detector, the number 000 meant there were no defects, any other number warned of a defect at the corresponding axle. If several were detected, small white lights on the top and bottom could also be displayed to inform the crews of multiple problems. Nevertheless, the conductor was still required to go into the bungalow, seaboard Air Line was the first railroad to install talking defect detectors. Beginning in the 1960s, their crews could hear the results of hotbox and dragging-equipment checks spoken over their radios in the engine cab. Over the years, as the use of this technology accelerated, for example, computerized, talking detectors allowed crews to interact with the detector using a touch tone function on their radios to recall the latest defect report. This eliminated any need for crews to walk to the location to confirm the radio reading. Sometimes the locations ambient temperature and train speed are also noted by the mechanical voice, crews can use their touch-tone hand radios to get the detector to repeat error messages. Defect detectors that are equipped with such a voice are often called talking detectors by railfans. To this day some rail lines, mostly passenger routes with a high traffic density, maintain centralized readout. This is due to the large and confusing volume of traffic a talking detector would generate. When an error signal is received a dispatcher or operator will contact the train via radio manually transmitting the error message, today defect detectors are often incorporated in monitoring platforms that are primarily used by railroads to more closely monitor the status of their trains
30.
Hall effect sensor
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A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall effect sensors are used for proximity switching, positioning, speed detection, in its simplest form, the sensor operates as an analog transducer, directly returning a voltage. With a known magnetic field, its distance from the Hall plate can be determined, using groups of sensors, the relative position of the magnet can be deduced. Frequently, a Hall sensor is combined with threshold detection so that it acts as and is called a switch and they can also be used in computer keyboards applications that require ultra-high reliability. Hall sensors are used to time the speed of wheels and shafts, such as for internal combustion engine ignition timing, tachometers. They are used in brushless DC electric motors to detect the position of the permanent magnet, in the pictured wheel with two equally spaced magnets, the voltage from the sensor will peak twice for each revolution. This arrangement is used to regulate the speed of disk drives. A Hall probe contains a compound semiconductor crystal such as indium antimonide, mounted on an aluminum backing plate. The plane of the crystal is perpendicular to the probe handle, connecting leads from the crystal are brought down through the handle to the circuit box. When the Hall probe is held so that the field lines are passing at right angles through the sensor of the probe. A current is passed through the crystal which, when placed in a field has a Hall effect voltage developed across it. The Hall effect is seen when a conductor is passed through a magnetic field. The natural electron drift of the charge causes the magnetic field to apply a Lorentz force to these charge carriers. The result is what is seen as a separation, with a buildup of either positive or negative charges on the bottom or on the top of the plate. The crystal measures 5 mm square, the probe handle, being made of a non-ferrous material, has no disturbing effect on the field. A Hall probe should be calibrated against a value of magnetic field strength. For a solenoid the Hall probe is placed in the center, when a beam of charged particles passes through a magnetic field, forces act on the particles and the beam is deflected from a straight path. The flow of electrons through a conductor is known as a beam of charged carriers, when a conductor is placed in a magnetic field perpendicular to the direction of the electrons, they will be deflected from a straight path
31.
Mass flow sensor
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A mass flow sensor is used to find out the mass flow rate of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the control unit to balance. Air changes its density as it expands and contracts with temperature and pressure, there are two common types of mass airflow sensors in use on automotive engines. These are the meter and the hot wire. Neither design employs technology that measures air mass directly, however, with additional sensors and inputs, an engines ECU can determine the mass flowrate of intake air. Both approaches are used almost exclusively on electronic fuel injection engines, both sensor designs output a 0. 0–5. Vehicles prior to 1996 could have MAF without an IAT, an example is 1994 Infiniti Q45. When a MAF sensor is used in conjunction with an oxygen sensor, the VAF sensor measures the air flow into the engine with a spring-loaded air vane attached to a variable resistor. The vane moves in proportion to the airflow, many VAF sensors have an air-fuel adjustment screw, which opens or closes a small air passage on the side of the VAF sensor. This screw controls the air-fuel mixture by letting a metered amount of air flow past the air flap, by turning the screw clockwise the mixture is enriched and counterclockwise the mixture is leaned. The vane moves because of the force of the air flow against it, it does not measure volume or mass directly. The drag force depends on air density, air velocity and the shape of the vane, some VAF sensors include an additional intake air temperature sensor to allow the engines ECU to calculate the density of the air, and the fuel delivery accordingly. In some manufacturers fuel pump control was part on the VAF internal wiring. A hot wire mass airflow sensor determines the mass of air flowing into the air intake system. The theory of operation of the hot wire mass airflow sensor is similar to that of the hot wire anemometer. This is achieved by heating a wire suspended in the air stream, like a toaster wire. The wires electrical resistance increases as the temperature increases, which varies the electrical current flowing through the circuit. When air flows past the wire, the wire cools, decreasing its resistance, as more current flows, the wire’s temperature increases until the resistance reaches equilibrium again
32.
Omniview technology
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Omniview technology is a vehicle parking assistant technology that became available in vehicle electronic products since around 2005. It is designed to help drivers in parking a vehicle in small space, early vehicle parking assistant products use radar or a single rear-view camera to get information about obstacles around, and provide drivers with sound alarm or rear-view video. There are some drawbacks about such products, the alarm is not intuitive, however, omniview technology overcomes these problems and has seen increasing applications since about 2005. In a common system, there are four wide-field cameras, one in the front of the vehicle, one in the back of the vehicle, one in the left rear view mirror. The four cameras cover the area around vehicle. The system synthesizes a bird view image in front of the vehicle by distortion correction, projection transformation, the images shown below are input and output of a common omniview product. Omniview suppliers Mobileye Israel Fujitsu Japan Percherry China
33.
Oxygen sensor
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An oxygen sensor is an electronic device that measures the proportion of oxygen in the gas or liquid being analysed. It was developed by Robert Bosch GmbH during the late 1960s under the supervision of Dr. Günter Bauman. The original sensing element is made with a thimble-shaped zirconia ceramic coated on both the exhaust and reference sides with a layer of platinum and comes in both heated and unheated forms. The planar-style sensor entered the market in 1990, and significantly reduced the mass of the sensing element as well as incorporating the heater within the ceramic structure. This resulted in a sensor that started sooner and responded faster, divers also use a similar device to measure the partial pressure of oxygen in their breathing gas. Scientists use oxygen sensors to measure respiration or production of oxygen, oxygen sensors are used in oxygen analyzers which find a lot of use in medical applications such as anesthesia monitors, respirators and oxygen concentrators. Oxygen sensors are used in hypoxic air fire prevention systems to monitor continuously the oxygen concentration inside the protected volumes. There are many different ways of measuring oxygen and these include such as zirconia, electrochemical, infrared, ultrasonic. Each method has its own advantages and disadvantages, automotive oxygen sensors, colloquially known as O2 sensors, make modern electronic fuel injection and emission control possible. They help determine, in time, if the air–fuel ratio of a combustion engine is rich or lean. Closed loop feedback-controlled fuel injection varies the fuel injector output according to sensor data rather than operating with a predetermined fuel map. In addition to enabling electronic fuel injection to work efficiently, this emissions control technique can reduce the amounts of both unburnt fuel and oxides of nitrogen entering the atmosphere. Volvo was the first automobile manufacturer to employ this technology in the late 1970s, the sensor does not actually measure oxygen concentration, but rather the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in air. Rich mixture causes an oxygen demand and this demand causes a voltage to build up, due to transportation of oxygen ions through the sensor layer. Lean mixture causes low voltage, since there is an oxygen excess, modern spark-ignited combustion engines use oxygen sensors and catalytic converters in order to reduce exhaust emissions. The ECU attempts to maintain, on average, a certain air–fuel ratio by interpreting the information it gains from the oxygen sensor. The primary goal is a compromise between power, fuel economy, and emissions, and in most cases is achieved by an air-fuel ratio close to stoichiometric, for spark-ignition engines, the three types of emissions modern systems are concerned with are, hydrocarbons, carbon monoxide and NOx. Tampering with or modifying the signal that the sensor sends to the engine computer can be detrimental to emissions control
34.
Parking sensor
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Parking sensors are proximity sensors for road vehicles designed to alert the driver to obstacles while parking. These systems use either electromagnetic or ultrasonic sensors, the sensors emit acoustic pulses, with a control unit measuring the return interval of each reflected signal and calculating object distances. Systems may also include visual aids, such as LED or LCD readouts to indicate object distance, a vehicle may include a vehicle pictogram on the cars infotainment screen, with a representation of the nearby objects as coloured blocks. Rear sensors may be activated when reverse gear is selected and deactivated as soon as any other gear is selected, front sensors may be activated manually and deactivated automatically when the vehicle reaches a pre-determined speed — to avoid subsequent nuisance warnings. Objects with flat surfaces angled from the vertical may deflect return sound waves away from the sensors, the Parking Sensor, originally called, ReverseAid, was a spin-off from the Sonic Pathfinder, an Electronic Guidance Device for the Blind. Both devices were invented in the late 1970s by Tony Heyes while working at the Blind Mobility Research Unit at Nottingham University in the UK, after patenting the device in 1983 Heyes offered it to Jaguar Cars in Coventry. After test driving the prototype on Heyess car they very politely told him that, real people would not want a thing like this. Heyes teamed up with a manufacturer and some 150 units were made and fitted to petrol tankers, trucks. Very few were fitted to private cars since few people wanted to drill holes in their cars, the electromagnetic parking sensor was re-invented and patented in 1992 by Mauro Del Signore. Electromagnetic sensors rely on the vehicle moving slowly and smoothly towards the object to be avoided, once detected, the obstacle, if the vehicle momentarily stops on its approach, the sensor continues to give signal of presence of the obstacle. If the vehicle then resumes its manoeuvre the alarm signal becomes more and more impressive as the obstacle approaches, now they also come equipped with a camera to go with the sensor. By 2018 the US is requiring back up camera with sensors on all cars, Blind spot monitors are an option that may include more than monitoring the sides of the vehicle. It can include Cross Traffic Alert, which alerts drivers backing out of a parking space when traffic is approaching from the sides, already in the 1970s German inventor Rainer Buchmann developed parking sensors
35.
Radar gun
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A radar speed gun is a device used to measure the speed of moving objects. A radar speed gun is a Doppler radar unit that may be hand-held, vehicle-mounted or static. The radar speed gun was invented by John L. Barker Sr. and Ben Midlock, originally, Automatic Signal was approached by Grumman Aircraft Corporation to solve the specific problem of terrestrial landing gear damage on the now-legendary PBY Catalina amphibious aircraft. Barker and Midlock cobbled a Doppler radar unit from coffee cans soldered shut to make microwave resonators, the unit was installed at the end of the runway, and aimed directly upward to measure the sink rate of landing PBYs. After the war, Barker and Midlock tested radar on the Merritt Parkway, in 1947, the system was tested by the Connecticut State Police in Glastonbury, Connecticut, initially for traffic surveys and issuing warnings to drivers for excessive speed. Starting in February 1949, the police began to issue speeding tickets based on the speed recorded by the radar device. In 1948, radar was used in Garden City, New York. Speed guns use Doppler radar to perform speed measurements, Radar speed guns, like other types of radar, consist of a radio transmitter and receiver. They send out a signal in a narrow beam, then receive the same signal back after it bounces off the target object. From that difference, the radar speed gun can calculate the speed of the object from which the waves have been bounced. After the returning waves are received, a signal with a equal to this difference is created by mixing the received radio signal with a little of the transmitted signal. Since this type of speed gun measures the difference in speed between a target and the gun itself, the gun must be stationary in order to give a correct reading. Instead of comparing the frequency of the signal reflected from the target with the transmitted signal, the frequency difference between these two signals gives the true speed of the target vehicle. Modern radar speed guns normally operate at X, K, Ka, Radar guns that operate using the X band frequency range are becoming less common because they produce a strong and easily detectable beam. Also, most automatic doors utilize radio waves in the X band range, as a result, K band and Ka band are most commonly used by police agencies. For these reasons, hand-held radar typically includes an on-off trigger, Radar detectors are illegal in some areas. Traffic radar comes in many models, hand-held units are mostly battery powered, and for the most part are used as stationary speed enforcement tools. Stationary radar can be mounted in vehicles and may have one or two antennae
36.
Speedometer
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A speedometer or a speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to vehicles, they started to be available as options in the 1900s. Speedometers for other vehicles have specific names and use other means of sensing speed, for a boat, this is a pit log. For an aircraft, this is an airspeed indicator, charles Babbage is credited with creating an early type of a speedometer, which were usually fitted to locomotives. The electric speedometer was invented by the Croatian Josip Belušić in 1888, originally patented by Otto Schultze on October 7,1902, it uses a rotating flexible cable usually driven by gearing linked to the output of the vehicles transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel, when the car or motorcycle is in motion, a speedometer gear assembly turns a speedometer cable, which then turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with an aluminum cup attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the magnetic field produces eddy currents in the cup. The effect is that the magnet exerts a torque on the cup, dragging it, the pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet, thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the currents on the cup is balanced by the opposing torque of the spring. At a given speed the pointer will remain motionless and pointing to the number on the speedometers dial. The return spring is calibrated such that a given speed of the cable corresponds to a specific speed indication on the speedometer. The sensor is typically a set of one or more magnets mounted on the shaft or differential crownwheel. As the part in question turns, the magnets or teeth pass beneath the sensor, alternatively, in more recent designs, some manufactures rely on pulses coming from the ABS wheel sensors. Most modern electronic speedometers have the additional ability over the current type to show the vehicle speed when moving in reverse gear. A computer converts the pulses to a speed and displays this speed on an electronically controlled, another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the cars wheel or transmission. The watch mechanism endeavors to push the speedometer pointer toward zero, the position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms
37.
Throttle position sensor
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A throttle position sensor is a sensor used to monitor the throttle position of a vehicle. The sensor is located on the butterfly spindle/shaft so that it can directly monitor the position of the throttle. More advanced forms of the sensor are used, for example an extra closed throttle position sensor may be employed to indicate that the throttle is completely closed. Related to the TPS are accelerator pedal sensors, which include a wide open throttle sensor. Modern day sensors are non contact type and these modern non contact TPS include Hall effect sensors, Inductive sensors, magnetoresistive and others. When the magnet/inductive loop mounted on the spindle which is rotated from the lower mechanical stop to WOT, the change in the magnetic field is sensed by the sensor and the voltage generated is given as the input to the ECU. Normally a two pole rare earth magnet is used for the TPS due to their high Curie temperatures required in the vehicle environment. The magnet may be of type, ring type, rectangular or segment type. The magnet is defined to have a magnetic field that does not vary significantly with time or temperature. In case of failure of the TPS operation the CHECK ENGINE light remains illuminated even if there is no problem or error in the ECU and it cannot be corrected by clearing ECU errors by running diagnostic software. In order to rectify the malfunction the TPS needs to be replaced by a new one
38.
Tire-pressure monitoring system
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A tire-pressure monitoring system is an electronic system designed to monitor the air pressure inside the pneumatic tires on various types of vehicles. TPMS report real-time tire-pressure information to the driver of the vehicle, either via a gauge, TPMS can be divided into two different types – direct and indirect. TPMS are provided both at an OEM level as well as an aftermarket solution, the target of a TPMS is avoiding traffic accidents, poor fuel economy, and increased tire wear due to under-inflated tires through early recognition of a hazardous state of the tires. Some claim the efficiency gains are negligible, the first passenger vehicle to adopt TPM was the Porsche 959 in 1986, using a hollow spoke wheel system developed by PSK. In 1996 Renault used the Michelin PAX system for the Scenic, the following year, Renault launched the Laguna II, the first high volume mid-size passenger vehicle in the world to be equipped with TPM as a standard feature. In the United States, TPM was introduced by General Motors for the 1991 model year for the Corvette in conjunction with Goodyear run-flat tires. The system uses sensors in the wheels and a display which can show tire pressure at any wheel. It has been standard on Corvettes ever since, the Firestone recall in the late 1990s, pushed the United States Congress to legislate the TREAD Act. The Act mandated the use of a suitable TPMS technology in all motor vehicles. This act affects all light motor vehicles sold after September 1,2007, phase-in started in October 2005 at 20%, and reached 100% for models produced after September 2007. In the United States, as of 2008 and the European Union, as of November 1,2012, from November 1,2014, all new passenger cars sold in the European Union must be equipped with a TPMS. For N1 vehicles, TPMS are not mandatory, but if a TPMS is fitted, on January 1,2013 for new models and on June 30,2014 for existing models. Japan is expected to adopt European Union legislation approximately one year after European Union implementation, further countries to make TPMS mandatory include Russia, Indonesia, the Philippines, Israel, Malaysia and Turkey. After the TREAD Act was passed, many companies responded to the opportunity by releasing TPMS products using battery-powered radio transmitter wheel modules. The introduction of run-flat tires and emergency spare tires by several tire, with run-flat tires, the driver will most likely not notice that a tire is running flat, hence the so-called run-flat warning systems were introduced. These are most often first generation, purely roll-radius based iTPMS, the iTPMS market has progressed as well. Indirect TPMS are able to detect under-inflation through combined use of roll radius and spectrum analysis, with this breakthrough, meeting the legal requirements is possible also with iTPMS. Indirect TPMS do not use physical pressure sensors but measure air pressures by monitoring individual wheel rotational speeds, first generation iTPMS systems are based on the principle that under-inflated tires have a slightly smaller diameter than a correctly inflated one
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