Introduction of NTC thermistor parameters.Photoresistance Vendor.SMD Thermistor company

　　【Nominal resistance value】

　　The nominal resistance value is the resistance value of the NTC thermistor design, which is often marked on the surface of the thermistor. The nominal resistance value refers to the zero-power resistance value when the reference temperature is 25°C, so it is also called the resistance value R25.

　　【rated power】

　　Rated power refers to the dissipated power allowed by the thermistor under long-term continuous load under the atmospheric conditions of ambient temperature of 25°C, relative humidity of 45% to 80% and atmospheric pressure of 0.87 to 1.07Pa.

　　【B value range】

　　The B value range (K) is the thermal index of a negative temperature coefficient thermistor and reflects the change in resistance between two temperatures. It is defined as the ratio of the difference between the natural logarithms of zero-power resistance values at two temperatures and the difference between the reciprocals of this temperature. The B value can be calculated by the following formula, that is, in the formula, R1 and R2 are the resistance values (Ω) at the absolute temperatures T1 and T2 respectively.

　　【Zero power resistance value】

　　The resistance value of the thermistor is measured at a specified temperature, and the resistance value measured when the resistance value change caused by the internal heating of the resistor can be ignored relative to the total measurement error.

　　【Dissipation coefficient δ(mW/℃)】

　　The dissipation factor is the ratio of the power dissipated by the thermistor to the change in ambient temperature, i.e.

　　In the formula, W is the power consumed by the thermistor (mW); T is the temperature at thermal equilibrium (°C); T0 is the ambient temperature (°C); I is the current through the thermistor when the temperature is T (A ); R is the resistance value (Ω) of the thermistor when the temperature is T.

　　【Time constant τ(s)】

　　The time constant τ(s) refers to the time required for the thermistor resistance to change by 63.2% when the ambient temperature changes from one specific temperature to another specific temperature in the zero power state.

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