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Thermistor
A thermistor is a semiconductor type of resistor in which the resistance is strongly dependent on temperature. The word ''thermistor'' is a portmanteau of ''thermal'' and ''resistor''. The varying resistance with temperature allows these devices to be used as temperature sensors, or to control current as a function of temperature. Some thermistors have decreasing resistance with temperature, while other types have increasing resistance with temperature. This allows them to be used for limiting current to cold circuits, e.g. for inrush current protection, or for limiting current to hot circuits, e.g. to prevent thermal runaway. Thermistors are categorized based on their conduction models. ''Negative-temperature-coefficient'' (NTC) thermistors have ''less'' resistance at ''higher'' temperatures, while ''positive-temperature-coefficient'' (PTC) thermistors have ''more'' resistance at ''higher'' temperatures. NTC thermistors are widely used as inrush current limiters and temperature ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inrush Current Limiter
An inrush current limiter is a component used to limit inrush current to avoid gradual damage to components and avoid blowing fuses or tripping circuit breakers. Negative temperature coefficient (NTC) thermistors and fixed resistors are often used to limit inrush current. NTC thermistors can be used as inrush-current limiting devices in power supply circuits when added in series with the circuit being protected. They present a higher resistance initially, which prevents large currents from flowing at turn-on. As current continues to flow, NTC thermistors heat up, allowing higher current flow during normal operation. NTC thermistors are usually much larger than measurement-type thermistors and are purposely designed for power applications. Thermistor An NTC thermistor's resistance is low at high temperatures. When the circuit is closed, the thermistor's resistance limits the initial current. After some time, current flow heats the thermistor, and its resistance changes to a lower ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inrush Current
Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform. Power converters also often have inrush currents much higher than their steady-state currents, due to the charging current of the input capacitance. The selection of over-current-protection devices such as fuses and circuit breakers is made more complicated when high inrush currents must be tolerated. The over-current protection must react quickly to overload or short-circuit faults but must not interrupt the circuit when the (usually harmless) inrush current flows. Capacitors A discharged or partially charged capacitor appears as a short circuit to the source when the source voltage is higher than the potential of the capacitor. A fully discharged capacitor will tak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steinhart–Hart Equation
The Steinhart–Hart equation is a model relating the varying electrical resistance of a semiconductor to its varying temperatures. The equation is : \frac = A + B \ln R + C (\ln R)^3, where : T is the temperature (in kelvins), : R is the resistance at T (in ohms), : A, B, and C are the Steinhart–Hart coefficients, which are characteristics specific to the bulk semiconductor material over a given temperature range of interest. Application When applying a thermistor device to measure temperature, the equation relates a measured resistance to the device temperature, or vice versa. Finding temperature from resistance and characteristics The equation model converts the resistance actually measured in a thermistor to its theoretical bulk temperature, with a closer approximation to actual temperature than simpler models, and valid over the entire working temperature range of the sensor. Steinhart–Hart coefficients for specific commercial devices are ordinarily reported by thermist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-regulating Heater
A positive-temperature-coefficient heating element (PTC heating element), or self-regulating heater, is an electrical resistance heater whose resistance increases significantly with temperature. The name ''self-regulating heater'' comes from the tendency of such heating elements to maintain a constant temperature when supplied by a given voltage. PTC heating elements are a type of thermistor. Properties PTC heating elements have large positive temperature coefficients of resistance, which means if a constant voltage is applied, the element produces a large amount of heat when its temperature is low, and a smaller amount of heat when its temperature is high. In comparison, most electrical heating elements also have positive temperature coefficients, but those coefficients are so small that the elements produce approximately the same amount of heat regardless of temperature. Self-regulating Some PTC heating elements are designed to have a sharp change in resistance at a part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperature Coefficient
A temperature coefficient describes the relative change of a physical property that is associated with a given change in temperature. For a property ''R'' that changes when the temperature changes by ''dT'', the temperature coefficient α is defined by the following equation: :\frac = \alpha\,dT Here α has the dimension of an inverse temperature and can be expressed e.g. in 1/K or K−1. If the temperature coefficient itself does not vary too much with temperature and \alpha\Delta T \ll 1, a linear approximation will be useful in estimating the value ''R'' of a property at a temperature ''T'', given its value ''R''0 at a reference temperature ''T''0: :R(T) = R(T_0)(1 + \alpha\Delta T), where Δ''T'' is the difference between ''T'' and ''T''0. For strongly temperature-dependent α, this approximation is only useful for small temperature differences Δ''T''. Temperature coefficients are specified for various applications, including electric and magnetic properties of materials a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm (), while electrical conductance is measured in siemens (S) (formerly called the 'mho' and then represented by ). The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance and low conductance, while objects made of electrical conductors like metals tend to have very low resistance and high conductance. This relationship is quantified by resistivity or conductivity. The nature of a material is not the only factor in resistance and conductance, however; it also depends on the size and shape of an object because these properties are extensive rather than in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resistance Thermometer
Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other constructions are also used. The RTD wire is a pure material, typically platinum (Pt), nickel (Ni), or copper (Cu). The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature. As RTD elements are fragile, they are often housed in protective probes. RTDs, which have higher accuracy and repeatability, are slowly replacing thermocouples in industrial applications below 600 °Celsius, C. Resistance/temperature relationship of metals Common RTD sensing elements for biomedical application constructed of platinum (Pt), nickel (Ni), or copper (Cu) have a repeatability, repeatable, resistance versus temperature relationship (''R'' vs ''T'') and operating temperature range. The ''R'' vs ''T'' re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resistor
A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat may be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity. Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds and forms. Resisto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NTC Bead
NTC may refer to: Education * Fort Irwin National Training Center, US Army training * Luther W. New Jr. Theological College, Dehradun, India * National Taitung Junior College, a college in Taitung County, Taiwan * National Technology Council (Pakistan) * National Teachers College, Philippines * National Trade Certificate Foundation, Mauritius * Nazarene Theological College (England) * New Teacher Center, US * Northcentral Technical College, US * Northfleet Technology College, UK * The Nautical Training Corps, UK Government * National Telecommunications Commission, Philippines * National Tracing Center, US firearms tracing facility * National Transitional Council (Congo) * National Transitional Council, Libya, August 2011–August 2012 * National Transport Commission, Australia * White House National Trade Council, established by US President Trump Telecommunications * Nepal Telecom * NTC Televisión, Colombia Other uses * Football South Australia National Training Ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nickel(III) Oxide
Nickel (III) oxide is the inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ... with the formula Ni2O3. It is not well characterized, and is sometimes referred to as black nickel oxide. Traces of Ni2O3 on nickel surfaces have been mentioned. Nickel (III) oxide has been studied theoretically since the early 1930s, supporting its unstable nature at standard temperatures. A nanostructured pure phase of the material was synthesized and stabilized for the first time in 2015 from the reaction of nickel(II) nitrate with sodium hypochlorite and characterized using powder X-ray diffraction and electron microscopy. References Inorganic compounds Catalysts Electrochemistry Transition metal oxides Nickel compounds Non-stoichiometric compounds Sesquioxides {{el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Failed NTC Thermistor
Failure is the social concept of not meeting a desirable or intended objective, and is usually viewed as the opposite of success. The criteria for failure depends on context, and may be relative to a particular observer or belief system. One person might consider a failure what another person considers a success, particularly in cases of direct competition or a zero-sum game. Similarly, the degree of success or failure in a situation may be differently viewed by distinct observers or participants, such that a situation that one considers to be a failure, another might consider to be a success, a qualified success or a neutral situation. It may also be difficult or impossible to ascertain whether a situation meets criteria for failure or success due to ambiguous or ill-defined definition of those criteria. Finding useful and effective criteria or heuristics to judge the success or failure of a situation may itself be a significant task. Sociology Cultural historian Scott San ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
