| Sensor technology is the modern measurement and automation systems technology, the development of the universe from the bottom of the sea exploration, production process control of modern civilization to life, almost every sensor technology can not be separated, in many countries of the sensor technology Attaches great importance to developing countries such as Japan to the six-sensor technology as the core technology (computers, communications, lasers, semiconductors, superconductors and sensors.) The various types of sensors in the pressure sensor with small size, light weight, high sensitivity, stability, reliability and low cost, ease of integration of the advantages, can be used in pressure, altitude, acceleration, liquid flow, flow, pressure liquid level measurement And control. In addition, it is widely used in water conservancy, geology, meteorology, chemical, medical and health, and so on. The plane is due to the technical process of combining with three-dimensional processing, and easy to integrate, and so can be used to make blood pressure monitors, anemometer, the total water velocity, pressure gauge, said, as well as electronic alarm devices. Pressure sensors have become various types of sensor technology in the most mature and most stable performance, cost-effective for a class of sensors. Therefore, for engaging in modern measurement and automatic control of the professional and technical personnel to understand and are familiar with at home and abroad pressure sensor status quo and development trends.
A pressure sensor the course of development
Modern pressure sensors in semiconductor sensors for signs of the invention, and the development of semiconductor sensors can be divided into four phases [1]:
(1) of the invention stage (1945 - 1960): This is the main phase of the bipolar transistor in 1947 marked the invention. Since then, the characteristics of semiconductor materials to be more widely used. Smith (CS Smith) and the 1945 discovery of germanium and silicon piezoresistive effect [2], that is, when there are external force in the semiconductor materials, its apparent resistance to change. Based on this principle is a pressure sensor made of the film strain Visco resistance in the metal film, the signal strength is about to be translated into electrical signals to measure. This phase of the minimum size of about 1cm.
(2) technology development phase (1960 - 1970): With the proliferation of silicon technology development, technical personnel in the silicon (001) or (110) crystal plane of the crystal to choose a suitable direct response to the spread of resistance in the surface of the crystal, And then processed into the back of the concave form a thin flexible silicon membrane, known as the Silicon Cup [3]. This form of silicon sensors Cup with a small size, light weight, high sensitivity, good stability, low cost and ease of integration of the advantages of the realization of the metal - a total of silicon crystal, for commercial development possible.
(3) integrated processed commercialization stage (1970 - 1980): Silicon Cup in the proliferation of theories on the basis of the application of the anisotropy of the corrosion of silicon technology, their sensors Si-proliferation process with the opposite sex corrosion of the silicon-based technology , Automatic control can be developed into a silicon membrane thickness of silicon processing technology anisotropy [4], there are V-shaped slot law, the automatic stay strong boron law, anodizing law automatically suspended microprocessor control and automatic suspension of law. Could be due to a number of surface corrosion at the same time, thousands of silicon membrane pressure can produce at the same time, to achieve the integration of the factory model, to further reduce costs.
(4) micro-machining stage (1980 - today): The end of the century's emerging nanotechnology, micro-machining technology makes possible. Through micro-machining process can be controlled by computer processing structure of a type of pressure sensor, can control the degree of its lines in the micron level. Processing can take advantage of this technology, micro-etching of the ditch, article, film, making micro pressure sensor into the stage.
2 at home and abroad pressure sensor research
From a global perspective of the development of pressure sensors mainly in the following directions.
2.1 fiber-optic pressure sensor [5]
This is a class of research results more sensors, but the actual investment in the field is not too much. Its working principle is to use pressure-sensitive components of the role of deformation and strength of the reflected light of the relevant characteristics of the box and the silicon thin film composed of chromium patch folder structure in the middle of a silicon fiber tailgate, where pressure Light through the tailgate in the process of intensity will change this by detecting tiny changes, we will be able to measured the size of the pressure. This sensor has been applied and clinical medicine, used to measure the expansion of coronary artery with a balloon catheter pressure. Foreseeable that the pressure sensor in certain aspects of microsurgery have good prospects for development. At the same time, in the processing and health care, and also the rapid development of fiber-optic sensors.
2.2 capacitive pressure sensor vacuum [6]
E + H's capacitive pressure sensor is a substrate and the thickness of 0. 8 ~ 2. 8mm of alumina (Al2O3) pose during a self-welding brazing ring together. The ring has a role in isolation, no temperature compensation, can maintain long-term reliability of measurement accuracy and long-lasting. Capacitance measurement method using principles of one-on-chip capacitance changes in the CP-bit, CP change with changes in pressure, the diaphragm displacement and the relationship between the pressure is linear. Encounter overload, the patch attached to the substrate will not be destroyed, no load will immediately back to the original position without any lag, the volume overload can be 100%, even if the damage is not leaking any medium pollution. Therefore, with a wide range of applications.
2.3 high temperature pressure sensor
New type of semiconductor material silicon carbide (SiC) single crystal made of the emergence of high-temperature sensor production possible. Rober. S. Okojie reported a test run up to 500 ¡æ the ¦Á (6H) SiC pressure sensor. The results show that the input voltage of 5V, the measured pressure for 6. 9MPa conditions, 23500 ¡æ at the time of full-scale Output for 44. 66 ~ 20. 03mV, full-range line for the degree of 20.17 percent, to slow 0.17 percent. At 500 ¡æ under the conditions of operation 10h, the performance will remain basically unchanged, and 100 ¡æ in the 500 ¡æ response of the two temperature coefficient (TCGF), were 20. 19% / ¡æ and - 0. 11% / ¡æ. The main priority of this sensor
Is the PN junction leakage current is very small, not hot match, as well as temperature variations do not have a plastic, bulk processing. Ziermann, Rene reported on the use of single crystal n-type ¦Â-SiC material made of pressure sensors, pressure sensors that temperature up to 573K, radiation-resistant. At room temperature, the pressure sensor with a sensitivity of 20. 2muV / VKPa.
2.4 silicon micro-machined sensor
Micro-machining technology in the improvement of today's silicon micro-mechanical sensors in the automobile industry more and more. With micro-mechanical sensors getting smaller and smaller in size, degree of line can be 1 ~ 2mm, can be placed in the body's vital organs in data collection. Hachol, Andrzej; dziuban, Jan Bochenek, a report can be used to measure the eye tonometer, the patch with a diameter of 1mm. 60mmHg, for intraocular pressure, static output 40mV, a high sensitivity factor.
2.5 self-test function of the pressure sensor
In order to reduce the cost of debugging and running, Dirk De Bruyker and others reported on a self-test function piezoresistive, capacitance sensor two-component, and its function in self-test is based on the principle of heat-driven, the sensor size 1. 2mm ¡Á 3mm ¡Á 0. 5mm, applicable to the biomedical field [7].
2.6 multi-axis force sensor
The six-axis force sensor research and application of multi-axis force sensor is a hot research now, only the United States, Japan and a few other countries can produce. China's Beijing Institute of Technology in tracking the development of foreign countries on the basis of the groundbreaking and have developed a combination of piezoelectric layer optical array of soft touch, the array density 2438tactels / cm2, power sensitive 1g, very flexible structure, able to grasp And to identify and hold an egg ball is now used for robot sorting items [8].
3 pressure sensors trend of development
Countries in the world today, the pressure sensor in the field is very wide, almost penetrated into all walks of life, can be summed up in the following trends:
(1) of the small market for small pressure sensor growing demand for such small sensors can work in extreme conditions, and only a small maintenance and repair work, the impact on the surrounding environment is also very small, Can be placed in the human body in all the vital organs in the collection of information does not affect people's normal life. Information platform such as the United States is the main function of the study and dissemination of environmental protection regulations and measures to implement information and technology, providing manufacturers with a lot of important information, such as:-EU directives and related laws and regulations; - national laws and regulations of the importing country, in particular with the EU's laws and regulations The differences between; - importer of WEEE recycling system; - with the WEEE and RoHS related standards and testing methods; - conformity assessment requirements of the importing country; - importing countries of the Organization of the attitude of industry and implementation of requirements; - dangerous substances to replace the technical line and dynamic ; - In line with the requirements of the materials, components and parts, such as databases;
(2) evaluation of the testing platform
The main function is to detect the platform to carry out testing and evaluation of dangerous substances, for the manufacturer to provide testing, evaluation and training services for manufacturers of self-declaration in line with the provision of technical support. Through the evaluation of the testing platform of saving the building and into the implementation of the directive to improve the professional standards of service. Proposed ways to integrate social resources, by the intermediary agencies, manufacturers, and for the support of the Government to build, operate independently. Entran range of production companies for 2 ~ 500PSI sensor with a diameter of only 1. 27mm, can be placed in the body's blood vessels without causing disruption to the flow of blood have a big impact.
(2) integrated pressure sensor has been an increasing number of measurements and other sensors used to form integrated measurement and control systems. Integrated System in factory automation and process control can improve the speed and efficiency of the operation.
(3) due to the integration of intelligent, integrated circuits can be added in a number of microprocessors, making the sensor with automatic compensation, communication, self-diagnosis and judge the logic functions.
(4) a wide range of pressure sensor is the other trends from the machinery industry to expand to other areas, such as: automotive components, medical equipment, energy and environmental control systems.
(5) standardization of the design and manufacture of sensors has been a certain industry standards. If the ISO international quality system; the United States AN2SI, ASTM standards, Russia's §¤OCT, Japan's J IS standard.
4 Conclusion
With the silicon, micro-machining technology, super-integrated circuit technology and materials with the properties of the progress made in the pressure transducer of optical fiber sensor production, high temperature piezoelectric and piezoresistive silicon sensor node applications possible, in bio-medical , In areas such as micro-mechanical, pressure sensors have broad application prospects. |
