Wireless Sensor Networks

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Wireless Sensor Networks

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The NTC thermistor (NTC is the abbreviation of Negative Temperature Coefficient) produced by our company is a high-density semiconductor ceramic component made of high-purity metal oxides such as Mn, Co, Ni, Fe, etc. sintered at high temperature. Its basic characteristics are that its resistance value decreases with increasing temperature, it does not generate signals itself, and its negative temperature coefficient is between -2 and -6%/℃. In recent years, NTC thermistors have been widely used in various temperature measurement and control and temperature compensation. They are becoming more and more mature in the fields of large and small household appliances, communication products, power tools, medical instruments, office automation equipment, etc., and are expanding to wider, broader, deeper and higher fields. NTC thermistors have shown their strong vitality and importance in the electronic, electrical and electromechanical manufacturing industries. KPD/MF58 Glass-sealed series NTC thermistor KPD/MF5A Epoxy-sealed series NTC thermistor KPD/SMD chip series NTC thermistor KPD/MF5K Thin film series NTC thermistor KPD/HAS Special sensor for small appliances KPD/BS Special sensor for battery pack Main technical parameters (1) Zero power resistance RT (Ω) RT refers to the resistance value measured at a specified temperature T, using a measurement power that causes a change in resistance that is negligible relative to the total measurement error. The relationship between resistance value and temperature change is: RT = RN expB(1/T – 1/TN) RT: NTC thermistor resistance 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 index. exp: exponent with natural number e as base (e = 2.71828 ...). This relationship is an empirical formula and has a certain accuracy only within a limited range of rated temperature TN or rated resistance RN, because the material constant B itself is also a function of temperature T. (2) Rated zero-power resistance R25 (Ω) According to the national standard, the rated zero-power resistance is the resistance R25 measured by the NTC thermistor at the reference temperature of 25 °C. This resistance value is the nominal resistance value of the NTC thermistor. The resistance value of the NTC thermistor usually refers to this value. (3) Material constant (thermal index) B value (K) The B value is defined as: RT1: zero-power resistance value 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 range is generally between 2000K and 6000K. (4) Zero-power resistance temperature coefficient (αT) The ratio of the relative change in the zero-power resistance value of the NTC thermistor at a specified temperature to the temperature change value that causes the change. αT: Zero-power resistance temperature coefficient at temperature T (K). RT: Zero-power resistance value at temperature T (K). T: Temperature (T). B: Material constant. (5) Dissipation factor (δ) At a specified ambient temperature, the dissipation factor of the NTC thermistor is the ratio of the change in power dissipated in the resistor to the corresponding temperature change of the resistor body. δ: NTC thermistor dissipation factor, (mW/K). △P: Power consumed by the NTC thermistor (mW). △T: The corresponding temperature change of the resistor body when the NTC thermistor consumes power △P (K). (6) Thermal time constant (τ) Under zero power conditions, when the temperature suddenly changes, the time required for the temperature of the thermistor to change by 63.2% of the difference between the initial and final temperatures. The thermal time constant is proportional to the heat capacity of the NTC thermistor and inversely proportional to its dissipation coefficient. τ: Thermal time constant (S). C: Heat capacity of the NTC thermistor. δ: Dissipation coefficient of the NTC thermistor. (7) Rated power Pn Under the specified technical conditions, the power that the thermistor is allowed to consume for long-term continuous operation. At this power, the temperature of the resistor body itself does not exceed its maximum operating temperature. (8) Maximum operating temperature Tmax Under the specified technical conditions, the maximum temperature that the thermistor can be allowed to operate continuously for a long time. That is: T0-ambient temperature. (9) Measurement power Pm Under the specified ambient temperature, the power consumed by the thermistor when the resistance change caused by the heating of the resistor body by the measurement current can be ignored relative to the total measurement error. Generally, the resistance change is required to be greater than 0.1%. Then the measured power Pm is: (10) Resistance-temperature characteristics The temperature characteristics of NTC thermistors can be approximately expressed by the following formula: Where: RT: zero-power resistance value at temperature T. A: coefficient related to the physical properties and geometric dimensions of the thermistor material. B: B value. T: temperature (k). A more precise expression is: Where: RT: zero-power resistance value of the thermistor at temperature T. T: absolute temperature value, K; A, B, C, D: specific constants.　　　

lorant

Quite good.