With the development of wearable smart devices, especially medical wearable smart devices, MEMS sensors are mainly relied on to detect various information of the wearer's body. So what is a MEMS sensor?
MEMS, or Microelectro Mechanical Systems, is a multidisciplinary frontier research field developed by MEMS sensors based on microelectronics technology. After more than 40 years of development, it has become one of the major scientific and technological fields in the world. It involves many disciplines and technologies such as electronics, mechanics, materials, physics, chemistry, biology, medicine, etc., and has broad application prospects.
As of 2010, there are more than 600 units in the world engaged in the research and production of MEMS. Hundreds of products including micro pressure sensors, accelerometers, micro inkjet printheads, and digital micromirror monitors have been developed. Among them, MEMS sensors account for a considerable proportion.
MEMS sensors are new sensors manufactured using microelectronics and micromachining technology. Compared with traditional sensors, it has the characteristics of small size, light weight, low cost, low power consumption, high reliability, suitable for mass production, easy integration and intelligentization. At the same time, the feature size on the order of micrometers makes it possible to perform functions not possible with some conventional mechanical sensors.
His main application has three aspects:
1. Applied to medical care
MEMS sensor is applied to non-invasive fetal heart rate detection. It is a very technical job to detect fetal heart rate. Because the fetal heart rate is very fast, between 20 and 160 times per minute, with traditional stethoscope or even ultrasound Doppler with amplification. It is difficult to measure accurately with manual counting. The ultrasonic Doppler fetal heart rate monitor with digital display function is expensive and is only used in a few large hospitals, and cannot be popularized in small and medium-sized hospitals and in vast rural areas. In addition, the ultrasonic vibration wave acts on the fetus, which has a great adverse effect on the fetus. Although the detection dose is very low, it is also a damage detection category, and is not suitable for regular and repetitive examinations and household use.
Based on VTI's MEMS accelerometer, a non-invasive fetal heart rate detection method was developed to develop a simple, easy-to-learn, intuitive and accurate clinical diagnosis between the fetal heart stethoscope and the Doppler fetal monitor. Auxiliary instrument.
The fetal heart rate is converted into an analog voltage signal by an acceleration sensor, and the difference is amplified by an instrument amplifier for preamplification. Then, a series of intermediate signal processing such as filtering is performed, and the analog voltage signal is converted into a digital signal by an A/D converter. The optical isolation device is input to the single chip microcomputer for analysis and processing, and finally the processing result is output.
The fetal heart rate tester based on the MEMS accelerometer design can be used as a terminal to make a remote fetal heart rate monitoring system. The central signal collection and analysis monitoring host at the hospital side gives the automatic analysis result, and the doctor diagnoses the result. If there is any problem, the pregnant woman is notified to the hospital in time. This technology is beneficial for pregnant women to check the condition of the fetus at any time, which is conducive to the health of the fetus and pregnant women.
2. Applied in automotive electronics
MEMS pressure sensors are mainly used to measure airbag pressure, fuel pressure, engine oil pressure, intake line pressure and tire pressure. The sensor uses single crystal silicon as a material to form a force sensitive diaphragm in the middle of the material by MEMS technology, and then diffuses impurities on the diaphragm to form four strain resistors, and then connects the strain resistors into a Wheatstone bridge. Circuitry to achieve high sensitivity. Automotive MEMS pressure sensors are available in several common forms such as capacitive, piezoresistive, differential transformer, and surface acoustic wave. The principle of MEMS accelerometer is based on Newton's classical mechanics law. It is usually composed of suspension system and detection quality. The acceleration is detected by the offset of micro silicon mass. It is mainly used in automotive airbag systems, anti-skid systems, and car navigation. In addition to capacitive and piezoresistive systems, MEMS accelerometers include piezoelectric, tunneling current, resonant, and thermocouple types. Among them, the capacitive MEMS accelerometer has the characteristics of high sensitivity and minimal temperature influence, and is the mainstream product in MEMS micro accelerometer. The microgyroscope is an angular rate sensor, which is mainly used for GPS signal compensation and automobile chassis control systems for car navigation, mainly including vibrating type and rotor type. The most widely used is a vibrating gyroscope that senses the angular velocity by using the Coriolis effect generated by the vibration mass of single crystal silicon or polycrystalline silicon when it is rotated by the susceptor. For example, when the car is turning, the system measures the angular velocity through the gyroscope to indicate whether the rotation of the steering wheel is in place, and actively applies appropriate braking on the inner or outer wheels to prevent the car from getting out of the lane. Usually, it forms active control together with the low accelerometer. system.
MEMS sensor for use in automobiles
3. Applied to the motion tracking system
In the daily training of athletes, MEMS sensors can be used to measure 3D human motion, record each action, and the coaches analyze the results and compare them repeatedly to improve the athletes' performance. With the further development of MEMS technology, the price of MEMS sensors will also decrease, which can be widely used in the Volkswagen gym.
In terms of skiing, pressure sensors, accelerometers, gyroscopes and GPS in 3D motion tracking allow users to obtain extremely accurate viewing capabilities. In addition to providing snowboard movement data, they can also record the user's position and distance. The same is true for surfing. The 3D motion tracking installed on the surfboard records information such as sea level, speed, surfing time, paddle distance, water temperature and calories burned.
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