The working principle of an ultrasonic sensor mainly involves three core processes: emission, propagation, and reception of ultrasonic waves. An ultrasonic sensor contains a piezoelectric crystal or magnetostrictive element. When current passes through these elements, mechanical vibrations are generated, thus producing ultrasonic waves. These ultrasonic waves are radiated outwards in the form of high-frequency sound waves (typically above 20kHz), and are reflected back to the receiver inside the sensor when they encounter an object. The applications of ultrasonic sensors are very extensive, including:
Car reversing radar: Detects obstacles behind the vehicle to help the driver reverse safely.
Automatic door sensors: Automatic doors in shopping malls, office buildings and other places use ultrasonic sensors to detect whether someone is approaching and then open the door automatically.
Industrial automation: In industrial production lines, it is used to detect the position, size, etc. of products and achieve automated control.
Robot navigation: Helps robots avoid obstacles and plan their paths.
Medical diagnostics: used to measure distances within the human body, such as the position and size of the fetus during prenatal checkups in pregnant women.
Environmental monitoring: Used for water quality monitoring, air quality monitoring, etc.
Ultrasonic sensors are characterized by non-contact detection, high precision, real-time performance, and wide environmental adaptability. They are virtually unaffected by environmental conditions such as light, dust, and fog, ensuring measurement accuracy. Furthermore, ultrasonic sensors feature temperature compensation, enabling them to maintain high-precision measurements over a wide temperature range.
Ultrasonic waves are mechanical waves with a vibration frequency higher than that of sound waves. They are characterized by high frequency, short wavelength, minimal diffraction, and, most importantly, good directionality, enabling them to propagate in a directional manner as rays. Several years ago, ultrasonic sensors were a backup option in the field of sensor technology. New technologies have made today's ultrasonic sensors extremely robust and durable with precise sensing capabilities. These enhanced characteristics have expanded into new application areas, completely surpassing the applications of traditional ultrasonic sensors.
Principles and performance indicators of ultrasonic sensors
Ultrasonic sensors are sensors developed using the properties of ultrasonic waves.
Ultrasound is a mechanical wave with a vibration frequency higher than that of sound waves. It is generated by the vibration of a transducer crystal under voltage excitation. It has the characteristics of high frequency, short wavelength, small diffraction, and especially good directionality, which allows it to propagate in a directional manner as a ray.
Ultrasound waves have a strong penetrating ability in liquids and solids, especially in solids that are opaque to sunlight, where they can penetrate to depths of tens of meters. When ultrasound waves encounter impurities or interfaces, they are significantly reflected, forming echoes. When they encounter moving objects, they produce the Doppler effect.
Therefore, ultrasonic testing is widely used in industry, national defense, biomedicine, and other fields. To use ultrasound as a testing method, it is necessary to generate and receive ultrasonic waves. The device that performs this function is an ultrasonic sensor, commonly referred to as an ultrasonic transducer or ultrasonic probe.
Ultrasonic sensors use the vibration of the pressure ceramic in the sensor head to generate high-frequency sound waves that are inaudible to the human ear for sensing. If these sound waves hit an object, the sensor can receive the reflected wave.
The sensor determines the distance to an object by measuring the wavelength of the sound wave and the time difference between emitting and receiving the returned sound wave. A sensor can be set to have both near and far distance settings via a button, and the sensor can detect the object regardless of which distance it is within.
Some ultrasonic sensors use separate transmitters and receivers. These through-beam or separate ultrasonic sensors are well-suited for detecting slow-moving objects, requiring rapid response, or operating in humid environments. Ultrasonic sensors are the preferred choice for detecting transparent objects, liquids, smooth, rough, glossy, and translucent surfaces, as well as irregularly shaped objects.
Ultrasonic sensors are not suitable for use in the following situations: outdoors, in extremely hot environments, inside pressurized containers, and they also cannot detect objects containing foam.
Ultrasonic sensors are mainly composed of piezoelectric crystals and can both emit and receive ultrasonic waves. Low-power ultrasonic probes are mostly used for detection. They come in many different structures, including straight probes (longitudinal waves), angled probes (transverse waves), surface wave probes (surface waves), Lamb wave probes (Lamb waves), and dual probes (one probe reflects and the other receives), etc.
The core of an ultrasonic probe is a piezoelectric crystal encased in a plastic or metal jacket. Many materials can be used to make the crystal. The size, diameter, and thickness of the crystal also vary, therefore the performance of each probe is different, and its performance must be understood before use.
An ultrasonic sensor is a sensor that converts ultrasonic signals into other energy signals (usually electrical signals). Ultrasonic waves are mechanical waves with vibration frequencies higher than 20kHz. They are characterized by high frequency, short wavelength, minimal diffraction, and, most importantly, good directionality, enabling them to propagate directionally as rays. Ultrasonic waves have a strong penetrating power through liquids and solids, especially in solids that are opaque to sunlight. When ultrasonic waves encounter impurities or interfaces, they produce significant reflections, forming reflected echoes. When they encounter moving objects, they produce the Doppler effect. Ultrasonic sensors are widely used in industry, defense, and biomedicine. Commonly used ultrasonic sensors consist of piezoelectric crystals and can both emit and receive ultrasonic waves. Low-power ultrasonic probes are mostly used for detection. They come in many different structures, including straight probes (longitudinal waves), angled probes (transverse waves), surface wave probes (surface waves), Lamb wave probes (Lamb waves), and dual probes (one probe emits, one probe receives), etc.
The working principle of an ultrasonic sensor mainly involves three core processes: the emission, propagation, and reception of ultrasonic waves. The following is a detailed explanation:
1. Launch process
Principle: An ultrasonic sensor contains a piezoelectric crystal or magnetostrictive element. When an electric current passes through these elements, mechanical vibrations are generated, which in turn produce ultrasonic waves. These ultrasonic waves are radiated outward in the form of high-frequency sound waves (typically above 20 kHz, beyond the range of human hearing).
Materials: The main materials of ultrasonic sensors include piezoelectric crystals (such as lead zirconate titanate PZT) and nickel-iron-aluminum alloys. These materials have electrostrictive or magnetostrictive properties, which can convert electrical energy into mechanical energy, thereby generating ultrasonic waves.
2. The propagation process
Medium: The emitted ultrasonic waves propagate through a medium (such as air, water, etc.). Their propagation speed is affected by the characteristics of the medium (such as temperature, pressure, and humidity). For example, the propagation speed in air is approximately 340 m/s, while in water it can reach as high as 1500 m/s.
Characteristics: During propagation, ultrasound waves undergo reflection, refraction, and absorption when encountering different media. In particular, significant reflected echoes are produced when ultrasound waves encounter impurities, interfaces, or moving objects.
3. Receiving process
Principle: An ultrasonic sensor has a piezoelectric ceramic element mounted on its housing. When an ultrasonic wave encounters the object being measured and is reflected back, this element receives the reflected wave and generates a tiny vibration. Subsequently, the vibration energy is converted into an electrical signal by the piezoelectric ceramic element.
Signal processing: The converted electrical signal is amplified by an amplifier circuit, ultimately resulting in a voltage signal proportional to the characteristics of the measured object (such as distance, size, etc.). This signal can be further processed and analyzed to obtain detailed information about the measured object.
Summarize
Ultrasonic sensors work by emitting ultrasonic signals, allowing them to propagate through a medium, and receiving the reflected signals to detect objects. By processing parameters such as the intensity and timing of the reflected signals, information such as the object's position, distance, and shape can be determined. Due to their non-contact, wear-free detection method, high precision, fast response, and strong anti-interference capabilities, ultrasonic sensors are widely used in various fields such as industrial inspection, medical diagnosis, and security monitoring.
