Basic characteristics of resistance of NTC thermistor.NSP Type Power Thermistor

　　The resistance-temperature characteristic of the thermistor can be approximated by the following formula: R=R0exp{B(1/T-1/T0)}: R: resistance value at temperature T (K), Ro: temperature T0, ( K) resistance value, B:B value, *T(K)=t(ºC)+273.15. In fact, the B value of the thermistor is not constant, and its variation varies depending on the material composition, up to a maximum of 5K/°C. Therefore, when formula 1 is applied in a large temperature range, there will be a certain error between the measured value and the actual value. Here, when the B value in Equation 1 is calculated as a function of temperature as shown in Equation 2, the error from the measured value can be reduced, and it can be considered to be approximately equal.

　　BT=CT2+DT+E, in the above formula, C, D, E are constants. In addition, the fluctuation of the B value due to different production conditions will cause the constant E to change, but the constants C and D remain unchanged. Therefore, when discussing the fluctuation amount of the B value, only the constant E can be considered. Calculation of constants C, D, E, constants C, D, E can be obtained from 4 points (temperature, resistance value) data (T0, R0). (T1, R1). (T2, R2) and (T3, R3), Calculated by formulas 3-6. First, obtain B1, B2, and B3 from the resistance values of T0, T1, T2, and T3 from pattern 3, and then substitute them into the following patterns.

　　Example of resistance value calculation: According to the resistance-temperature characteristic table, find the resistance value of 5(kΩ) at 25°C and the resistance value of the thermistor with a B value deviation of 50(K) at 10°C～30°C . Step (1) According to the resistance-temperature characteristic table, find the constants C, D and E. To=25+273.15T1=10+273.15T2=20+273.15T3=30+273.15 (2) Substitute BT=CT2+DT+E+50 to find BT. (3) Substitute the value into R=5exp {(BT1/T-1/298.15)} to find R. *T: 10+273.15～30+273.15.

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