How does the self-inductive hand dryer work

November 20, 2018

The hand dryer is a sanitary appliance for quickly drying hands. It is available in both automatic and manual. Mainly used in hotels, restaurants, medical food, public facilities, office buildings, personal homes and other places. The common hand dryers used in daily life generally adopt the automatic induction method. When the hands are close, the heating device is activated to dry the hands. The use of automatic sensing is more convenient and hygienic, and can avoid cross-infection, especially suitable for occasions with high requirements for sanitary conditions.

Hand Dryer

The automatic induction of self-inductive hand dryers is mainly based on the principle of infrared heat radiation. The heat of the human hand is detected by an infrared sensor to control the opening and closing of the heating device. Since all objects with temperatures above absolute zero emit infrared radiation, and the thermal effects of infrared radiation are more pronounced than other radiations, infrared radiation is often preferred to measure temperature.

When the human hand is close to the position where the infrared sensor of the hand dryer is directly opposite, the infrared radiation emitted by the human hand is absorbed by it, resulting in a corresponding change in its physical characteristics. The general infrared temperature sensor uses a thermistor inside. For an infrared sensor composed of a thermistor with different temperature coefficients, the resistance increases or decreases when the temperature rises. Finally, this change is converted into a voltage change by an external measuring circuit. When the control system detects this voltage change, the heating device is activated; when the human hand leaves, the voltage returns to the original value, and the control system turns off the heating device. In order to achieve a simple power saving effect.

The GE ZTP-148SR thermopile infrared sensor is used for non-contact measurement of the surface temperature of the object. The ZTP-148SR includes a thermal sensing section, an IR filter, and a thermostat for temperature compensation in a hermetic TO-46 package. At the same time, GE also offers a variety of filters to achieve the best performance in a variety of applications.

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