Thermistors are highly favored in the field of temperature sensing and circuit compensation due to their significant resistance temperature characteristics. The core parameter B value (material constant) accurately describes the law of resistance changing with temperature, and is the cornerstone of selection and circuit design. It is crucial to master a reliable method for calculating the B value of thermistors.
Understanding the physical meaning of B value is the foundation of calculation. It essentially reflects the average energy activation energy of thermistor materials within a specific temperature range, measured in Kelvin (K). The larger the B value, the more sensitive the resistance is to temperature changes. This is a key indicator for evaluating the performance of thermistors.
The core formula for calculating the B value of a thermistor is derived based on its resistance temperature characteristic equation (simplified version of Steinhart Hart equation)
B = [T1 * T2 / (T2 – T1)] * ln(R1 / R2)
Among them, T1 and T2 are absolute temperatures (in K, converted to Celsius temperature+273.15), and R1 and R2 are the resistance values measured by the thermistor at temperatures T1 and T2, respectively. This formula is the core tool for calculating B values.
The actual B value measurement method usually follows the following steps:
1. Select two characteristic temperature points (such as 25 ° C and 50 ° C or 85 ° C), accurately measure the ambient temperature and convert it into T1 and T2.
2. In a constant temperature environment, use a precision bridge or multimeter to accurately measure the resistance values R1 and R2 of the thermistor at T1 and T2.
3. Substitute T1, T2, R1, and R2 into the above formula for calculating the B value accurately.
To improve the reliability of the results, measurements can be taken at multiple temperature points and the least squares method can be used to fit and obtain a more accurate B value. A standardized measurement method is a prerequisite for accurate results.
By mastering the calculation method of thermistor B value, engineers can scientifically select components with suitable B values based on the temperature range and accuracy requirements of the target application, and optimize the performance of temperature detection or compensation circuits. The precise calculation method is directly related to the reliability and accuracy of the final application, and is the core technical link for the successful application of thermistors.
