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A thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors. The word is a portmanteau of ''thermal'' and ''resistor''. Thermistors are widely used as inrush current limiter, temperature sensors (NTC type typically), self-resetting overcurrent protectors, and self-regulating heating elements. Thermistors differ from resistance temperature detectors (RTDs) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a greater precision within a limited temperature range, typically −90 °C to 130 °C.〔("NTC Thermistors" ). Micro-chip Technologies. 2010.〕 ==Basic operation== Assuming, as a first-order approximation, that the relationship between resistance and temperature is linear, then: : where :, change in resistance :, change in temperature :, first-order temperature coefficient of resistance Thermistors can be classified into two types, depending on the classification of ''''. If '''' is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, or posistor. If '''' 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 a '''' as close to 0 as possible, so that their resistance remains nearly constant over a wide temperature range. Instead of the temperature coefficient ''k'', sometimes the ''temperature coefficient of resistance'' (alpha sub T) is used. It is defined as〔(Thermistor Terminology ). U.S. Sensor〕 : This coefficient should not be confused with the parameter below. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「thermistor」の詳細全文を読む スポンサード リンク
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