Thermistor

Definition: Thermistor

Thermistor

Noun

1. A semiconductor device made of materials whose resistance varies as a function of temperature; can be used to compensate for temperature variation in other components of a circuit.

Specialty Definitions: Thermistor

Domain	Definitions
Aerospace	An electron device employing the temperature- dependent change of resistivity of a semiconductor. (references)
Electrical Engineering	A resistor whose resistance varies greatly with temperature, but which shows substantially ohmic behaviour at any given(internal)temperature. Source: European Union. (references)
Mining	An electrical resistor made of a material whose resistance varies sharply in a known manner with the temperature. Thermistors are commonly used for shipboard oceanographic temperature measurements because of their percentage response to unit temperature change and their greatsensitivity. (references)
Source: compiled by the editor from various references; see credits.

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Specialty Definition: Thermistor

(From Wikipedia, the free Encyclopedia)

A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature.

If we assume that the relationship between resistance and temperature is linear (i.e. we make a first-order approximation), then we can say that:

where

ΔR = change in resistance

ΔT = change in temperature

k = first-order temperature coefficient of resistance

Thermistors can be classified into two types depending on the sign of k. If k is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, or posistor. If k is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) thermistor. Resistors that are not thermistors are designed to have the smallest possible k, so that their resistance remains almost constant over a wide temperature range.

Steinhart Hart equation

In practice, the linear approximation (above) works only over a small temperature range. For accurate temperature measurements, the resistance/temperature curve of the device must be described in more detail. The Steinhart-Hart equation is a widely used third-order approximation:

where a, b and c are called the Steinhart-Hart parameters, and must be specified for each device. T is the temperature in kelvin and R is the resistance in ohms. To give resistance as a function of temperature, the above can be rearranged into:

where

and

Conduction model

Many NTC thermistors are made from a thin coil of semiconducting material such as a sintered metal oxide. They work because raising the temperature of a semiconductor increases the number of electrons able to move about and carry charge - it promotes them into the conducting band. The more charge carriers that are available, the more current a material can conduct. This is described in the formula:

i=nAve

Where i is current, n is the number of charge carriers, A is area of the material, v is voltage and e is the charge on an electron.

The current is measured using an ammeter. Over large changes in temperature, callibration is necessary. However, this is unnecessary if the right semiconductor is used, because over small changes in temperature the resistance of the material is linearly proportional to the temperature. There are many different semiconducting thermistors and their range goes from about 0.01 kelvin to 2000 kelvin (approx. 1700°C)

Applications

Thermistor is used in smart flash for cameras which will shut off for proper film exposure according to the light bounced back.
PTC thermistors can be used as current-limiting devices for circuit protection, as replacements for fuses. Current through the device causes a small amount of resistive heating. If the current is large enough to generate more heat than the device can lose to its surroundings, the device heats up, causing its resistance to increase, and therefore causing even more heating. This creates a self-reinforcing effect that drives the resistance upwards until the thermistor breaks the circuit.

References

I.S. Steinhart & S.R. Hart in "Deep Sea Research" vol. 15 p. 497 (1968) - in which the Steinhart-Hart equation was first published.

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Thermistor."

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Abbreviations & Acronyms: Thermistor

The following table is compiled from various sources, across various languages. When English abbreviations or acronyms come from a non-English source, this is noted.
Entry	Source	Expression	Field
Thermistor	English	Thermally sensitive resistor	Economics
Source: compiled by the editor, based on several corpora (additional references).

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Synonym: Thermistor

Synonym: thermal resistor (n). (additional references)

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Synonyms within Context: Thermistor

Context	Synonyms within Context (source: adapted from Roget's Thesaurus).
Measurement	Bathometer, galvanometer, heliometer, interferometer, odometer, ombrometer, pantometer, pluviometer, pneumatometer, pneumometer, radiometer, refractometer, respirometer, rheometer, spirometer, telemeter, udometer, vacuometer, variometer, viameter, thermometer, thermistor (heat), barometer (air), anemometer (wind), dynamometer, goniometer (angle) meter; landmark; (limit); balance, scale; (weight); marigraph, pneumatograph, stethograph; rain gauge, rain gage; voltmeter(volts), ammeter(amps); spectrophotometer (light absorbance); mass spectrophotometer(molecular mass); geiger counter, scintillation counter(radioactivity); pycnometer (liquid density); graduated cylinder, volumetric flask (volume); radar gun (velocity); radar (distance); side-looking radar (shape, topography); sonar (depth in water); light meter (light intensity); clock, watch, stopwatch, chronometer (time); anemometer (wind velocity); densitometer (color intensity).
Thermometer	Noun: thermometer, thermometrograph, mercury thermometer, alcohol thermometer, clinical thermometer, dry-bulb thermometer, wet-bulb thermometer, Anschutz thermometer, gas thermometer, telethermometer; color-changing temperature indicator; thermopile, thermoscope; pyrometer, calorimeter, bomb calorimeter; thermistor, thermocouple.
Source: adapted from Roget's Thesaurus.

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Crosswords: Thermistor

Specialty definitions using "thermistor": final resistance ♦ positive-temperature-coefficient thermistor final resistance, PTC thermistor final resistance ♦ temperature profile recorder. (references)

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Non-Fiction Usage: Thermistor

Subject	Topic	Quote
Health		Primary among these sensors are the abdominal strain gauge, inductance plethysmograph, and nasal thermistor. (references)
Source: compiled by the editor from ICON Group International, Inc.; see credits.

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Usage Frequency: Thermistor

"Thermistor" is generally used as a noun (singular) -- approximately 100.00% of the time. "Thermistor" is used about 3 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted)

Parts of Speech	Percent	Usage per 100 Million Words	Rank in English
Noun (singular)	100%	3	202,518

Source: compiled by the editor from several corpora; see credits.

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Expression: Thermistor

Expression using "thermistor": PTC thermistor final resistance. Additional references.
Source: compiled by the editor from various references; see credits.

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Frequency of Internet Keywords: Thermistor

The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com.

Expression	Frequency per Day
thermistor	223
ntc thermistor	14
ptc thermistor	7
thermistor sensor	7
thermistor probe	6
circuit thermistor	6
quality thermistor	4
thermistor manufacturer	3
fenwal thermistor	2
120 ptc thermistor	2
medical probe thermistor	2
datasheet thermistor	2
circuit design thermistor	2
Source: compiled by the editor from various references; see credits.

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Modern Translations: Thermistor

Language		Translations for "thermistor"; alternative meanings/domain in parentheses.
Chinese		热敏�"�阻. (various references)

Danish		termistor, varmemodstand, halvledermodstandstermometer (semiconductor resistance thermometer). (various references)

Dutch		thermoweerstand, thermistor, weerstandsthermometer met halfgeleider (semiconductor resistance thermometer). (various references)

Finnish		termistori. (various references)

French		thermomètre � semi-conducteurs ou thermistances (semiconductor resistance thermometer), thermistor, thermistance. (various references)

German		Thermistor (termistor, thermal resistor), temperaturgesteuerter Widerstand, Heissleiter (termistor, thermal resistor), Heißleiter, Halbleiterwiderstandsthermometer (semiconductor resistance thermometer). (various references)

Greek		θερμόμετρο με ημιαγωγούς (semiconductor resistance thermometer), θερμική αντίσταση, θερμοστάτης (thermostat, water regulator), θερμίστορ. (various references)

Italian		thermistance, termoresistenza, termometro a semiconduttori (semiconductor resistance thermometer), termistore, termistenza. (various references)

Japanese Kanji		サーボ機構 (cermet, cum, cycasin, cycle, cyclic, cycling, cycling course, cyclist, psi, psychics, salmon, salmon pink, science, science fiction, scientific, scientist, scientology, Searle, semen, servomechanism, sialon, sirloin, sirloin steak, sperm, thermal printer, thermoconcrete, thermoelement, thermometer, thermostat, thiabendazole). (various references)

Japanese Katakana		サーミスター . (various references)

Pig Latin		ermistorthay

Portuguese		termistor, termómetro de semi-condutores (semiconductor resistance thermometer). (various references)

Russian		терморезистор. (various references)

Spanish		termistor (semiconductor resistance thermometer), termistancia, resistencia térmica (semiconductor resistance thermometer). (various references)

Swedish		termistor. (various references)
Source: compiled by the editor from various translation references.

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Derivations: Thermistor

Derivations
	Words beginning with "thermistor": thermistors. (additional references)
Source: compiled by the editor, based on several corpora (additional references).

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Anagrams: Thermistor

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "e-h-i-m-o-r-r-s-t-t"
	-1 letter: remittors.
	-2 letters: heritors, isotherm, mortiser, mothiest, omitters, remittor, stormier, theorist, thirster, thorites.
	-3 letters: erotism, heriots, heritor, hermits, heroism, hitters, hoister, homiest, horsier, metrist, mithers, moister, mortise, mothers, mothier, omitter, retorts, retrims, rhetors, rioters, ritters, roister, rotters, shorter, shortie, smother, stertor, termors, territs, thermos, thorite, tithers, tremors, trimers, trisome.
	-4 letters: heriot, hermit, hirers, hitter, homers.
	Words containing the letters "e-h-i-m-o-r-r-s-t-t"
	+1 letter: thermistors.
	+3 letters: thermometries, thermotropism, trimethoprims.
	+4 letters: aromatherapist, petrochemistry, thermotropisms.
	+5 letters: anthropometries, aromatherapists, stereochemistry, thermochemistry.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.