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With the widespread use of smartphones, people have noticed that when making or receiving calls, the phone screen automatically turns off when the face approaches the screen and turns back on, unlocking itself when the face moves away by a certain distance. This feature primarily prevents accidental screen touches caused by the face during calls. A key component enabling this function is the distance sensor. In fact, distance sensors have extensive applications—not only in smartphones but also in aerospace, industrial manufacturing, and daily life. This article will provide you with a detailed introduction to distance sensors.
Distance sensors broadly refer to any sensor capable of measuring distance. Specifically, they include:
Sensors that measure distance based on the time-of-flight principle.
Sensors that generate signals in response to changes in distance.
Distance sensors emit energy waves that reflect off objects. By calculating the time it takes for the emitted wave to reflect back, the sensor determines the distance to the object.
Currently, distance sensors are commonly classified by the type of energy wave they emit, including ultrasonic distance sensors, laser distance sensors, infrared distance sensors, and 24 GHz radar sensors.
Ultrasonic Distance Sensors
Ultrasonic distance sensors use ultrasonic waves as the energy source to measure distance. They are widely used due to their speed, convenience, simple calculation, and real-time control capability. Their measurement accuracy meets industrial requirements, making them popular in mobile robot development.
Ultrasound is a mechanical wave with a frequency higher than audible sound, generated by piezoelectric elements vibrating under electrical excitation. It features high frequency, short wavelength, minimal diffraction, excellent directionality, and propagates in a focused beam. Ultrasonic waves have strong penetration ability through liquids and solids, especially opaque solids, penetrating up to several tens of meters. When encountering impurities or interfaces, ultrasound reflects strongly, producing echo signals. Moving objects cause Doppler effects.
Therefore, ultrasonic detection is widely used in industries such as defense and biomedical fields. Devices that generate and receive ultrasound to measure distance are ultrasonic distance sensors.
Laser Distance Sensors
Laser distance sensors use lasers as the light source. They can be divided into continuous-wave and pulsed laser types. Solid-state lasers like ruby and Nd:glass are used for pulsed laser ranging, while gas lasers such as helium-neon, argon-ion, and krypton-cadmium operate in continuous output mode for phase laser ranging.
Due to lasers' monochromaticity and strong directionality, combined with semiconductor electronic circuit integration, laser distance meters can operate day and night, achieve high accuracy, reduce weight and power consumption, and measure distances to distant targets such as artificial satellites and the moon.
Infrared Distance Sensors
Infrared distance sensors feature paired infrared emitters and receivers. The LDM301 infrared distance sensor emits an infrared beam that reflects off a target object. The reflected signal is received, and the time difference between emission and reception is processed by a CCD-based image processor to calculate the distance.
This method works on natural surfaces and reflective plates. Infrared distance sensors offer long-range measurement and high-frequency response, making them suitable for harsh industrial environments.
24 GHz Radar Sensors
24 GHz radar sensors convert microwave echo signals into electrical signals. They serve as core components in radar speedometers, water level gauges, automotive adaptive cruise control (ACC) systems, and automatic door sensors.
By emitting and receiving microwaves around 24.125 GHz, they detect object presence, movement speed, static distance, and angle. Using planar microstrip antenna technology, these sensors are compact, highly integrated, and highly sensitive.
Today's industrial solutions are becoming smarter and more convenient. To meet these demands, industrial systems must incorporate various types of sensors. Distance sensors act as the antennas of industrial networks, enabling measurement, detection, feedback, and control functions. As a professional distance sensors company, BST offers reed sensors, Hall sensors, and inductive sensors with excellent performance, suitable for applications such as proximity sensing, flow measurement, and liquid level detection.
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