Development of new sensor technologies
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Preface: A sensor is a device that converts physical quantities, chemical quantities, and biomass into electrical signals. The output signal has different forms, such as voltage, current, frequency, pulse, etc. It can meet the requirements of information transmission, processing, recording, display, and control. It is an indispensable element in automatic detection systems and automatic control systems. If the computer is compared to the brain, then the sensor is equivalent to facial features. The sensor can correctly sense the measured value and convert it into the corresponding output, which plays a decisive role in the quality of the system. The higher the degree of automation, the higher the sensor requirements of the system.
In today's information age, the information industry includes information acquisition, transmission, and processing, namely sensing technology, communication technology, and computer technology. With the rapid development of ultra-large-scale integrated circuits, modern computer technology and communication technology have been fully developed. Not only do they require more and more precision, reliability, response speed, and the amount of information to be acquired, but they also require low cost. Easy to use. Obviously, traditional sensors have gradually been eliminated because their functions, characteristics, volume, and cost have been difficult to meet. Many developed countries in the world are accelerating the research and development of new sensor technologies and have made great breakthroughs. Nowadays, the development of new sensor technologies mainly includes the following aspects:
First, discovering and utilizing new phenomena using physical phenomena, chemical reactions, and biological effects as the principle of sensors. Therefore, it has been found that new phenomena and new effects are important tasks in the development of sensor technology and are the basis for the research and development of new types of sensors.
Japan Sharp Corporation uses superconductivity technology to develop a successful high-temperature superconducting magnetic sensor, which is a major breakthrough in sensor technology. Its sensitivity is high, second only to superconducting quantum interference devices. Its manufacturing process is far simpler than superconducting quantum interference devices. Can be used for magnetic imaging technology, has a wide range of promotional value.
When the antibody and the antigen meet and combine on the surface of the electrode, the potential of the electrode is changed, and an immunosensor can be produced by using this phenomenon. Immunosensors made with this antibody can check for the presence of this antigen in a living organism. If you use hepatitis virus antibodies to check whether someone has hepatitis, play a fast and accurate role. The University of California has developed such sensors.
Second, the use of new materials Sensor materials is an important basis for sensor technology, due to advances in material science, people can create a variety of new sensors. For example, a temperature sensor made of a polymer film; optical fiber can be made into a variety of pressure, flow, temperature, displacement and other sensors; made of ceramic pressure sensor.
Polymers absorb and release water molecules in proportion to the relative humidity of the surrounding environment. The polymer dielectric constant is small, and water molecules can increase the dielectric constant of the polymer. The polymer electrolyte is made into a capacitor, and the relative humidity is determined by measuring the change in capacitance. Using this principle, a plasma polymerized polystyrene film temperature sensor is made, which has the following characteristics:
â—† Wide range of moisture measurement;
◆ wide temperature range, up to -400 °C ~ +1500 °C;
â—† Fast response, less than 1S;
â—† Small size, can be used for measuring humidity in a small space;
â—† The temperature coefficient is small.
The ceramic capacitive pressure sensor is a dry pressure sensor without intermediate fluid. Adopting advanced ceramic technology and thick-film electronic technology, its technical performance is stable. The annual drift is less than 0.1% FS. The temperature drift is less than ±0.15%/10K, and the anti-overload is strong, which can reach hundreds of times of the range. The measuring range can be from 0 to 60 MPa. German E+H company and American Kavlio company's products are in the leading position.
The application of optical fiber is a major breakthrough in sensing materials, and it was first used in optical communication technology. In the use of optical communication, it is found that when the environmental conditions such as temperature, pressure, electric field, and magnetic field change, the intensity, phase, frequency, polarization, etc. of the optical fiber transmitted by the optical fiber are changed, and the change in the amount of the optical wave is measured, and it is known that these optical wave quantities are changed. The temperature, pressure, electric field, magnetic field and other physical quantities can be used to develop optical fiber sensors. Compared with traditional sensors, fiber-optic sensors have many characteristics: high sensitivity, simple structure, small size, corrosion resistance, good electrical insulation, flexible optical path, and easy implementation of telemetry. Optical fiber sensor Japan is at an advanced level. Such as IdecIzumi company and Sunx company. The combination of fiber-optic sensor and integrated optical path technology accelerates the development of fiber-optic sensor technology. The integrated optical circuit device replaces the original optical component and the passive optical device, so that the optical fiber sensor has high bandwidth, low signal processing voltage, high reliability, and low cost.
Third, micro-machining technology Semiconductor technology processing methods include oxidation, photolithography, diffusion, deposition, planar electronic process, anisotropic etching and evaporation, sputtering film, etc., these have been introduced to the sensor manufacturing. As a result, various new types of sensors have been produced, such as the use of semiconductor technology to fabricate silicon microsensors, the use of thin-film processes to fabricate fast-responding gas- and moisture-sensitive sensors, and the use of sputtered-film technology to fabricate pressure sensors.
Yokogawa Japan uses anisotropic etching technology for high-precision three-dimensional processing, making an all-silicon resonant pressure sensor. The core part is composed of two resonant beams fabricated on the pressure sensitive silicon diaphragm and the silicon diaphragm. The frequency difference of the two resonant beams corresponds to different pressures. The pressure is measured by the frequency difference method, which can eliminate errors caused by factors such as ambient temperature. . When the ambient temperature changes, the frequency and amplitude of the two resonant beams change in the same way. After the two frequencies are different, the same amount of change can cancel each other out. Its measurement accuracy is up to 0.01%FS.
US SiliconMicrostructure Inc. (SMI) has developed a series of low-cost silicon micro-pressure sensors with linearity in the range of 0.1% to 0.65%, with a minimum full-scale range of 0.15 psi (1KPa). It is made of silicon and has unique characteristics. The three-dimensional structure, light micro machining, and multiple etching made the Wheatstone bridge on the silicon diaphragm. When the force is applied to the top of the silicon wafer, it deforms, and the resistance generates a piezoresistive effect and loses the bridge balance. Electric signals proportional to pressure. Silicon microsensors such as this are cutting-edge technologies for the development of today's sensors. Its basic feature is that the volume of sensitive components is in the order of micrometers, which is tens or hundreds of percent of conventional sensors. It plays an important role in industrial control, aerospace, and biomedicine, such as the use of aircraft to reduce aircraft weight and reduce energy. Another feature is that it can be measured sensitively and can be made into a blood pressure sensor.
The CYJ series sputtering film pressure sensor developed by the Beijing Institute of Measurement and Control Technology, China National Aviation Corporation, is a metal strain gauge processed by ion sputtering technology. It overcomes the disadvantages of non-metal strain gauges susceptible to temperature and has high stability. It is applicable to all kinds of occasions, and has a wide range of measured media. It also overcomes the disadvantages of low precision, large hysteresis, and creep caused by traditional adhesive tapes. It has the characteristics of high precision, high reliability, and small size. It is widely used in aviation. , petroleum, chemical, medical and other fields.
IV. Integrated Sensors The advantages of integrated sensors are that they cannot be achieved by traditional sensors. It is not just a simple sensor. It integrates the components in the auxiliary circuit and the sensing element on one chip at the same time, making it calibrated, compensated, and self-contained. Diagnostic and network communication functions, which can reduce costs, increase production, the United States LUCAS, Novasensor developed the blood pressure sensor, can produce 10,000 per week.
V. Intelligent Sensor The intelligent sensor is a microprocessor-based sensor, which is a combination of a microcomputer and a sensor. It combines detection, judgment, and information processing functions. Compared with traditional sensors, it has many features:
â—† With judgment and information processing functions, the measurement value can be corrected and error compensated, thus improving the measurement accuracy;
â—†Multi-sensor multi-parameter measurement can be realized;
â—† Self-diagnosis and self-calibration function to improve reliability;
â—† Measurement data can be accessed and used conveniently;
â—† Data communication interface, able to communicate directly with the microcomputer.
The sensor, signal conditioning circuit, and MCU are integrated on one chip to form an ultra-large-scale integrated advanced smart sensor. The United States HONYWELL ST-3000 smart sensor, the chip size is only 3 × 4 × 2mm3, the use of semiconductor technology, made in the same chip CPU, EPROM, static pressure, pressure, temperature and other three kinds of sensitive components.
Research and development of intelligent sensors, the United States is in a leading position. NASA called this sensor a Smart Sensor when developing spacecraft. This type of sensor is very important in spacecraft. China's research and development in this area is still lagging behind, mainly because of the limited level of technology of semiconductor integrated circuits in China.
The development of sensors is changing with each passing day. Especially since humans have entered the information age with a high degree of industrialization, sensor technology has been updated to newer technologies. The developed countries of the United States, Japan, and other developed countries have the fastest development of sensor technologies. Because of the weak foundation in China, there is a big gap between sensor technology and these developed countries. Therefore, we should increase investment in the research and development of sensor technology, shorten the gap between China's sensor technology and foreign countries, and promote the development of China's instrumentation industry and self-sufficiency technology.