What is NTC thermistor

NTC Negative Temperature Coefficient Thermistor Working Principle NTC is the abbreviation of Negative Temperature Coefficient, meaning negative temperature coefficient, referring to the negative temperature coefficient of semiconductor materials or components, the so-called NTC thermistor is the negative temperature coefficient thermistor. The so-called NTC thermistor is a negative temperature coefficient thermistor, which is made of metal oxides such as manganese, cobalt, nickel, and copper as the main material, and is manufactured using ceramic technology. These metal oxide materials are semiconducting in nature, as they are completely similar to semiconducting materials such as germanium and silicon in the way they conduct electricity. When the temperature is low, the number of carriers (electrons and holes) of these oxide materials is small, so its resistance value is high; as the temperature rises, the number of carriers increases, so the resistance value decreases. ntc thermistor in the range of 10O ~ 1000000 ohm at room temperature, temperature coefficient of -2%~-6.5%. ntc thermistor can be ntc thermistor is widely used in temperature measurement, temperature control, temperature compensation, etc. NTC thermistor can be widely used in temperature measurement, temperature control, temperature compensation, NTC thermistor can be widely used in temperature measurement, temperature control, temperature compensation, etc.　NTC Negative Temperature Coefficient Thermistor NTC (Negative Temperature Coeff1Cient) is a thermistor phenomenon and material with a negative temperature coefficient, with the temperature rise of the resistance decreased exponentially. The material is the use of manganese, copper, silicon, cobalt, iron, nickel, zinc and other two or more metal oxides for adequate mixing, molding, sintering and other processes made of semiconductor ceramics, can be made with a negative temperature coefficient (NTC) of the thermistor. Its resistivity and material constants with the material composition ratio, sintering atmosphere, sintering temperature and structure of different states and changes. Now also appeared to silicon carbide, tin selenide, tantalum nitride, etc. as the representative of the non-oxide system NTC thermistor materials.　NTC thermal semi-conducting ceramics are mostly spinel structure or other structure of the oxide ceramics, with a negative temperature coefficient, the resistance value can be approximated as follows: where RT, RT0 for the temperature T, T0 when the resistance value, Bn for the material constant. Ceramic grain itself due to temperature changes in resistivity changes, which is determined by the semiconductor properties.　NTC negative temperature coefficient thermistor history NTC thermistor development has gone through a long stage. 1834, scientists first discovered a negative temperature coefficient of silver sulfide characteristics. 1930, scientists found that cuprous oxide - copper oxide also has a negative temperature coefficient of performance, and will be successfully used in the temperature compensation circuit of aviation instruments. Subsequently, due to the continuous development of transistor technology, thermistor research has made significant progress. 1960 developed a NTC thermistor.　NTC negative temperature coefficient thermistor temperature range Its measurement range is generally -10 ~ +300 ℃, can also be done -200 ~ +10 ℃, and can even be used for +300 ~ +1200 ℃ environment for temperature measurement.　　Negative temperature coefficient thermistor thermometer accuracy can reach 0.1 ℃, temperature sensing time can be less than 10s. It is not only suitable for grain silo thermometer, but also can be applied to food storage, medicine and health, scientific planting, the ocean, deep wells, high altitude, glaciers and other aspects of temperature measurement.

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NTC Characteristic Curve[1]

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NTC Negative Temperature Coefficient Thermistor Terminology Zero-power Resistance RT (Ω) RT refers to the resistance value measured at a specified temperature T using a measurement power that causes negligible resistance value change relative to the total measurement error. at a specified temperature T.　The relationship between resistance value and temperature change is: RT = RN expB(1/T - 1/TN) RT : Resistance value of NTC thermistor at temperature T (K).　RN : NTC thermistor resistance at rated temperature TN (K).　T : Specified temperature (K).　B : Material constant of NTC thermistor, also called thermal exponent.　exp: Exponent based on a natural number e (e = 2.71828 ...).　This relationship is empirical and is only accurate within a limited range of rated temperatures TN or rated resistance values RN, since the material constant B is itself a function of temperature T. The material constant B is also a function of temperature T, which is a function of temperature.　Rated Zero Power Resistance R25 (Ω) According to the national standard, the rated zero power resistance is the resistance value of NTC thermistor measured at the reference temperature of 25 ℃, which is the nominal resistance value of NTC thermistor. This value is the nominal resistance value of the NTC thermistor, and is often referred to as the resistance value of the NTC thermistor.　Material Constant (Thermal Index) B Value (K) The B value is defined as: RT1: Zero power resistance at temperature T1 (K).　RT2: Zero power resistance value at temperature T2 (K).　T1, T2: Two specified temperatures (K).　For commonly used NTC thermistors, the B value ranges from 2000K to 6000K.　Temperature Coefficient of Zero Power Resistance (αT) The ratio of the relative change in the zero power resistance value of an NTC thermistor at a specified temperature to the value of the temperature change that caused the change.　αT : Temperature coefficient of zero power resistance at temperature T (K).　RT : Zero power resistance value at temperature T (K).　T : Temperature (T).　B: Material constant.　Dissipation coefficient (δ) The dissipation coefficient of an NTC thermistor is the ratio of the change in power dissipated in the resistor to the corresponding change in temperature of the resistor at a specified ambient temperature.　δ: Dissipation factor of NTC thermistor, (mW/ K).　Δ P : Power dissipated by the NTC thermistor (mW).　Δ T : Temperature change (K) of the resistor when the NTC thermistor consumes power (Δ P).　Thermal time constant (τ) The time required for the temperature of the thermistor to change by 63.2% of the difference between the first and last temperatures when the temperature changes suddenly under the condition of zero power, which is directly proportional to the heat capacity of the NTC thermistor and inversely proportional to its dissipation factor.　τ: Thermal time constant (S).　C: Thermal capacity of the NTC thermistor.　δ: Dissipation factor of NTC thermistor.　Rated power Pn Under the specified technical conditions, the power allowed to be consumed by the thermistor for long-term continuous operation. Under this power, the temperature of the resistor body itself does not exceed its maximum operating temperature.　Maximum Operating Temperature Tmax Under the specified technical conditions, the maximum temperature allowed for long-term continuous operation of the thermistor. I.e.: T0 - ambient temperature.　Measuring Power Pm The power consumed by a thermistor at a specified ambient temperature when the resistance value change caused by heating of the resistor body by the measuring current is negligible in relation to the total measuring error.　The general requirement of resistance value change is greater than 0.1%, then the measurement power Pm is: Resistance Temperature Characteristics The temperature characteristics of the NTC thermistor can be approximated by the following formula: Where: RT: Zero power resistance value at temperature T. A: Zero power resistance value at temperature T.　A: coefficient related to the physical properties and geometry of the thermistor material.　　B: B value.　T: temperature (k).　A more accurate expression is as follows: Where: RT: zero power resistance value of thermistor at temperature T.　T: is the absolute temperature value, K; A, B, C, D: are specific constants.　 Temperature Control Application Design Electronic thermometer, electronic calendar, electronic clock temperature display, electronic gifts; cooling and heating equipment, heating and thermostat appliances; automotive electronics temperature measurement and control circuit; temperature sensors, temperature meters; medical electronic equipment, electronic washing equipment; cell phone batteries and charging appliances.

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