NTC thermist resistance heat time constant.Human Body Temperature Monitoring Sensor Factory

　　The heat time constant refers to the time that the thermistor temperature sensor costs 63.2%of the total difference between the initial and the final body temperature; when the temperature changes by the ladder function. In short, it represents the time required for a thermistor to return to 50%of its initial resistance.

　　When measuring the heat time constant, you need to apply a temperature change. However, if this change is too slow, it will be measured by the measurement environment, not the corresponding reaction based on the changes in thermal resistance. Therefore, it is necessary to use a change in instantaneous temperature as close as possible. That is the hot time constant of NTC thermistor. Usually use to indicate the hot time constant.

　　The following formulas are used to explain the hot time constant

　　Under zero power conditions, when the temperature occurs, the temperature of the thermistor resistance changes at 63.2%of the temperature difference between the beginning and end. Heat time constant τ is directly proportional to the thermal capacity C of the thermistor resistance, which is inversely proportional to its dispersing coefficient Δ, that is,

　　τ = C/Δ

　　s: Hot time constant (s).

　　C: Thermal capacity of NTC thermal resistance.

　　Δ: Disposal coefficient of NTC thermistor.

　　Measurement of hot time constant:

　　The most commonly used method for measuring the thermal time constant of NTC thermistor is to place the device in the static air at room temperature. Then apply enough power to make the temperature of the thermistor is much higher than the ambient temperature. Keep electricity until it achieves heat stability at high temperature. Then remove the power supply from the thermistor and trigger the timer at the same time. Continuously monitor the NTC thermistor, and stop stopped when the timer indicates that the NTC thermistor is cooled to 63.2%, indicating the temperature difference between the high temperature and the ambient temperature. The time indicates the heat time constant, usually in seconds.

　　Factors that affect the constant constant of the heat time constant:

　　The quality of thermistor

　　The shape of the thermistor (structure and volume)

　　Packaged materials for temperature sensor packaging

　　"Environment" —— gas or liquid thermistor resistance

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