NTC resistance heat time constant definition and calculation formula.Radar Microwave Induction Sensor Switch

　　NTC thermal resistance is a semiconductor ceramic component made of transition metal oxides as the main raw material. It has a very large negative temperature coefficient. The resistance value changes with the heating of the ambient or due to the current temperature or it produces self -heating. That is, at a certain measurement power, the resistance value drops rapidly as the temperature rises. Using this feature, the NTC thermistor can be determined by measuring its resistance to determine the corresponding temperature to achieve the purpose of detecting and controlling the temperature.

　　The definition of hot time constant:

　　The hot time constant refers to the time that it takes a heat -sensitive resistor temperature sensor under the condition of zero to change the original and the final temperature of 63.2%of the total; when the temperature varies from a step -jump function. How long does it take to restore the initial resistance value of 50%of thermal resistance.

　　When measuring the heat time constant, you need to apply a temperature change. However, if this change is too slow, you will only be measured by the measurement of the environment, not the reaction of the change of thermal resistance. Therefore, it is important to use an instantaneous temperature change as much as possible.

　　The heat time constant is directly proportional to the thermal capacity of NTC thermistor, which is inversely proportional to its dispersal coefficient.

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