Abstract: Acceleration sensor is a kind of equipment to measure acceleration force by sensing acceleration and converting it into electrical signal. Acceleration sensor has a wide range of functions and has been widely used in many fields, such as automobile safety, intelligent products, game control and so on. So what is the working principle of the acceleration sensor? Different kinds of acceleration sensors have different working principles. Let's take a closer look at them. 1. What is the working principle of the acceleration sensor?

Most acceleration sensors work on the principle of piezoelectric effect. The so-called piezoelectric effect is that "the external force exerted on the heteropolar crystal without symmetry center will not only deform the crystal, but also change the polarization state of the crystal and establish an electric field inside the crystal." The phenomenon that this medium is polarized by mechanical force is called positive piezoelectric effect.

Generally speaking, the acceleration sensor uses the crystal deformation caused by its internal acceleration. Because this deformation will generate voltage, as long as the relationship between the generated voltage and the applied acceleration is calculated, the acceleration can be converted into voltage output. Of course, there are many methods to make acceleration sensors, such as piezoresistive technology, capacitance effect, thermal bubble effect, light effect, etc., but the most basic principle is that a medium is deformed due to acceleration, and this deformation is measured and converted into voltage output through related circuits. Each technology has its own opportunities and problems.

Second, the classification of acceleration sensors

1, piezoelectric type

Piezoelectric accelerometer is also called piezoelectric accelerometer. It also belongs to inertial sensor. The principle of piezoelectric accelerometer is to use the piezoelectric effect of piezoelectric ceramics or time-sensitive crystals. When the accelerometer vibrates, the force exerted by the mass on the piezoelectric element will also change. When the measured vibration frequency is much lower than the natural frequency of the accelerometer, the change of force is directly proportional to the measured acceleration.

2, piezoresistive type

Based on the world-leading MEMS silicon micromachining technology, piezoresistive acceleration sensor has the characteristics of small volume and low power consumption, and is easy to be integrated into various analog and digital circuits, and is widely used in automobile crash experiments, test instruments, equipment vibration monitoring and other fields.

3. Capacitance

Capacitive acceleration sensor is a variable polar distance capacitive sensor based on capacitance principle. Capacitive accelerometer/capacitive accelerometer is a common acceleration sensor. It is irreplaceable in some fields, such as airbags, mobile phones and mobile devices. Capacitive accelerometer/capacitive accelerometer adopts MEMS technology, which becomes economical in mass production, thus ensuring lower cost.

4. Servo type

Servo acceleration sensor is a closed-loop test system with good dynamic performance, large dynamic range and good linearity. Its working principle is that the vibration system of the sensor consists of an "m-k" system, which is the same as the general accelerometer, except that the mass M is connected with an electromagnetic coil. When there is acceleration input on the base, the mass deviates from the equilibrium position, which is detected by the displacement sensor, amplified by the servo amplifier and converted into current output. The current flows through the electromagnetic coil, which produces electromagnetic restoring force in the magnetic field of the permanent magnet, trying to keep the mass in its original equilibrium position in the instrument housing. The feedback function enhances the anti-interference ability, improves the measurement accuracy and expands the measurement range. Servo acceleration measurement technology is widely used in inertial navigation and inertial guidance systems, as well as in high-precision vibration measurement and calibration.

Third, the role of acceleration sensor

The function of the acceleration sensor is to measure the acceleration and get the acceleration value. Several common application scenarios of acceleration sensors are as follows.

1, game control

The acceleration sensor can detect the change of tilt angle, so it is very simple to control the object in the game by tilting the handheld device back and forth.

2. Earthquake detection

Geophone is a special sensor for geological exploration and engineering survey. It is a sensor that converts ground vibration into electrical signals. It can convert the ground vibration caused by seismic waves into electrical signals, which are converted into binary data by A/D converter for data organization, storage and operation.

3. Car accident alarm

With the rapid development of automobile industry, automobile has become one of the main means of transportation for people to travel, but the number of casualties caused by traffic accidents is also very huge. In the modern information age, using high technology to save people's lives will be one of the main research topics. The car accident alarm system based on acceleration is based on this design concept, and it is believed that the popularization of this system will bring more safety to the automobile industry.

4, pedometer function

The acceleration sensor can detect AC signals and the vibration of objects. When people walk, they will generate certain regular vibration, and the acceleration sensor can detect the zero-crossing point of the vibration, so as to calculate the number of steps people walk or run, and then calculate the displacement of people moving. And the heat consumption can be calculated by a certain formula.

5. Attitude detection of equipment or terminal

Acceleration sensors and gyroscopes are usually called inertial sensors, which are often used in various devices or terminals to realize attitude detection and motion detection, so they are very suitable for people who play somatosensory games. The acceleration sensor can use gravity acceleration to detect the inclination angle of the equipment, but it will be affected by motion acceleration, which makes the inclination angle measurement inaccurate, so gyroscope and magnetic sensor are usually used to compensate. At the same time, when the magnetic sensor measures the orientation, it also uses the geomagnetic field. When the current in the system changes or there is magnetic conductive material around it, and the equipment tilts, the measured azimuth angle is also inaccurate. At this time, acceleration sensors (tilt sensors) and gyroscopes are needed to compensate.

In addition to the above, acceleration sensors are also widely used in many fields, such as handle vibration and shaking, automobile brake start detection, engineering vibration measurement, geological exploration, vibration testing and analysis, safety vibration reconnaissance and so on.