Material constant of the thermistor

The material constant of the thermistor, that is, the thermistor chip (a kind of semiconducting ceramic), after being sintered at a high temperature, forms a material having a certain resistivity, and each formulation and sintering temperature has only one B value, so the material is a material. constant. The B value can be calculated by measuring the resistance values at 25 degrees Celsius and 50 degrees Celsius (or 85 degrees Celsius). The B value is positively correlated with the product temperature coefficient of resistance, that is, the larger the B value, the larger the temperature coefficient of resistance.

The temperature coefficient refers to the rate of change of the resistance value for every 1 degree increase in temperature. The B value can be converted into the temperature coefficient of resistance by the following formula: temperature coefficient of resistance = B value / T^2 (T is the point temperature value to be converted). The B value of the NTC thermistor is generally between 2000K and 6000K. It cannot be said simply that the larger the B value, the better or the smaller, the better. It depends on where it is used. In general, as a product for temperature measurement, temperature compensation, and suppression of surge resistance, the B value is better under the same conditions. Because the product with a large B value changes its resistance value more with the change of temperature, that is to say, it is more sensitive.

Thermistors are semiconductor devices fabricated using the temperature-dependent characteristics of the resistivity of semiconductor materials. The thermistor time constant τ is a parameter describing the thermal inertia of the thermistor. It is defined as the time required for the temperature change of the thermistor to reach 63% of the difference between the temperature of the thermistor and the ambient temperature. The time constants of the thermistors vary widely.