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NTC Thermistor and Fire Alarm
2020/01/16 03:01:07


EXSENSE Electronic Technology Co., Ltd. uses advanced semiconductor processes technology, combines with independent intellectual property rights of NTC thermistor materials and processing technology, to ensure the reliability and stability of continuous production of thermistor. NTC thermistor researched, developed and produced by our company, because of its high precision, high sensitivity, cost effective, etc., which is widely used in smart home, office supplies, medical equipment, security equipment and other application fields.


Fire alarm plays a key role for the prevention of fires at homes, public places, reduce the loss of people's property. NTC thermistors also play an integral role in fire alarms - temperature monitoring. Today, EXSENSE Electronics introduce the operation of the fire alarm.


Fire alarm monitors the ambient temperature through the NTC thermistor and automatically sounds the alarm in the event of a fire. The thermistor is used because the resistance value of NTC thermistor varies with temperature. Compared with other components, it’s more sensitive to temperature. Fire alarms include power supplies, NTC thermistors, potentiometer, capacitor, transistor, resistor, diodes, and buzzer. Fire alarm operates according to the switching characteristic of transistor; Thermistor and resistor form the voltage divider network that drives the transistor. Because thermistor is sensitive to temperature, as the ambient temperature rises, the resistance value of the thermistor in the fire alarm decreases, and vice versa. Because the transistor is turned on by the voltage drop on the resistor, if the ambient temperature is in the normal range, the resistance value of the NTC thermistor will be larger, and the voltage of the thermistor will also be large according to Ohm's Law V=IR (the threshold voltage can be set by changing the potentiometer). In this case, the resistance voltage will be too low enough to turn on the transistor. As a result, as the ambient temperature gradually increases beyond the normal range, the resistance value of the NTC thermistor decreases and the pressure drop of the resistance increases, thus turning on the transistor. When the transistor is turned on, the buzzer starts and an alarm sounds. The diode is used in a fire alarm to ensure that one-way conduction. Capacitors are used to eliminate the transient of NTC thermistors.

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