The influence of indoor air quality on people is very important. The use of sensors to detect air quality is a popular method. This paper introduces the application of sensors in air quality detection, analyzes the advantages and disadvantages of current gas sensors, and gas sensors. Development trends and prospects.
Air quality gas sensor indoor environmental pollution
First, the importance of air for people People can not do without oxygen every moment, and get oxygen by inhaling air. An adult needs to inhale 6500 liters of air per day to get enough oxygen. Therefore, the polluted air has a direct impact on human health. More than 90% of a person's life is spent indoors. It can be seen that the impact of indoor air quality on people is even more crucial.
Second, indoor environmental pollution background Today, human beings are facing "coal smoke pollution", "photochemical smog pollution", and then the emergence of "indoor air pollution"-based third environmental pollution. American experts have found that there are more than 500 kinds of volatile organic compounds in indoor air, including more than 20 kinds of carcinogens and more than 200 kinds of pathogenic viruses. The main hazards are: antimony, formaldehyde, benzene, ammonia and esters, trichloroethylene and so on. A large number of shocking facts have confirmed that indoor air pollution has become a "stealth killer" that endangers human health and has become a common concern of all countries in the world. According to statistics, nearly half of the world's people are in indoor air pollution, indoor environmental pollution has caused 35.7% of respiratory diseases, 22% of chronic lung disease and 15% of bronchitis, bronchitis and lung cancer.
III. Some ideas on the development of indoor air quality services 1. Investigate the basic situation of air quality in domestic households and offices. 2. Understand and introduce the introduction of indoor air quality testing equipment. 3. To carry out large-scale publicity activities, the meteorological department and the environmental protection department should jointly establish a management mechanism for indoor air quality problems. 4. Conduct special investigation and research on the regulations, technical standards, indoor pollution measurement methods and measuring instruments of the indoor environmental quality of the international environmental protection department.
Fourth, the powerful weapon of air detector - sensor detection technology is an indispensable important technical means for people to understand and transform the world. The sensor is an important tool for the acquisition, transmission and processing of information resources in scientific experiments and industrial production activities. Six sensors that play an important role in air quality testing are described below. 1. Metal oxide semiconductor sensor. The metal oxide semiconductor sensor utilizes the adsorption of the gas to be measured to change the conductivity of the semiconductor, and the alarm circuit is excited by the comparison of the current changes. Since the semiconductor sensor is greatly affected by the environment during measurement, the output line shape is unstable. Metal oxide semiconductor sensors, because of their very sensitive response, are widely used in the field of measuring gas micro-leakage. 2. Catalytic combustion sensor. The principle of catalytic combustion sensor is one of the most widely used principles for detecting combustible gas. It has the characteristics of good output signal shape, reliable index, low price and no cross interference with other non-combustible gases. The catalytic combustion sensor adopts the Wheatstone bridge principle. The induction resistance and the flammable gas in the environment are flamelessly burned. The temperature changes the resistance of the induction resistor, breaks the balance of the bridge, and outputs a stable current signal. The amplification, stabilization, and processing of the later circuits ultimately show reliable values. 3. Constant potential electrolytic sensor. The constant potential electrolytic sensor is one of the most widely used technologies in the field of measuring poisons. In this respect, foreign technology is leading, so most of these sensors rely on imports. Structure of a constant potential electrolytic gas sensor: a working electrode, a counter electrode and a reference electrode are mounted in a cylindrical cell made of plastic, and an electrolyte is filled between the electrodes, and a separator made of porous tetrafluoroethylene is Top package. The connection between the preamplifier and the sensor electrode applies a certain potential between the electrodes to put the sensor in operation. The gas and the working electrode in the electrolyte undergo oxidation or reduction reaction, and the equilibrium potential of the electrode changes in the reduction or oxidation reaction of the counter electrode, and the change value is proportional to the gas concentration. 4. Gavny battery type oxygen sensor. The structure of the Galvanic battery-type oxygen sensor: a polytetrafluoroethylene gas permeable membrane with a thickness of 10-30 μm, which is well permeable to oxygen, is placed on one side of the plastic container, and a precious metal (platinum, gold, silver) is adhered to the inside of the container. The cathode electrode forms an anode on the inside of the other side of the container or in the vacant portion of the container (a metal having a large ionization tendency such as lead or cadmium). Use potassium hydroxide. When oxygen passes through the electrolyte, it undergoes a redox reaction at the anode and cathode, ionizing the anode metal, and releasing electrons. The magnitude of the current is proportional to the amount of oxygen. Since the anode metal is consumed in the whole reaction, the sensor needs to be periodically replaced. At present, domestic technology has become increasingly mature, and it is entirely possible to localize such sensors 5. Infrared sensors. The infrared sensor utilizes the absorption principle of various elements for a specific wavelength, has good anti-toxicity, is responsive, and reacts to most hydrocarbons. However, the structure is complicated and the cost is high. 6. PID photo ionization gas sensor. The PID consists of a main part such as an ultraviolet lamp light source and an ion chamber. The positive and negative electrodes in the ion chamber form an electric field. The gas to be measured is ionized under the irradiation of the ultraviolet lamp to generate positive and negative ions, and a current is formed between the electrodes. signal. PID has the advantages of high sensitivity, no poisoning problem, safety and reliability.
V. In-depth analysis of the development status of gas detection instrumentation industry In recent years, with the rapid development of China's economy, the instrumentation industry has also developed rapidly. Since 2004, the production and sales have exceeded 100 billion yuan for the first time, and the industry has entered a fast lane. In 2006, the total output value of the industry exceeded 200 billion yuan; in 2007, the total output value of the instrumentation industry reached 307.8 billion yuan, with a growth rate of 28.5%; according to the statistics of the Instrument and Meter Industry Association, the total output value of the instrumentation industry in the first half of 2008 reached 175.59 billion yuan. The growth rate was 23.8% year-on-year, among which the growth rate of analytical instruments and environmental monitoring instruments was as high as 32%.
The advancement of science and technology has provided conditions for the development of the gas detection instrumentation industry. The promotion of market and government policies, the improvement of people's safety awareness, and the improvement of relevant laws and regulations are the core driving forces for the development of the gas detection industry. These promote the gas detection instrumentation. The industry is in a period of rapid industrial growth. From the perspective of technological development, according to the principle of using sensors, common gas detection instruments and meters have applicable gas and application fields, and new technologies and new products are becoming the mainstream of future gas detection instruments.
6. Prospects for future air quality testing With the continuous improvement of people's living standards and increasing emphasis on environmental protection, the detection of various toxic and harmful gases, the monitoring of air pollution, industrial waste gas and the quality of food and living environment Testing has placed higher demands on gas sensors. The successful application of new materials development technologies such as nanometer and thin film technology provides a good precondition for gas sensor integration and intelligence. Gas sensors will be developed on the basis of multi-disciplinary integrated technologies such as micromachine and microelectronics, computer technology, signal processing technology, sensing technology, fault diagnosis technology, and intelligent technology. The development of fully automatic digital intelligent gas sensors capable of simultaneously monitoring multiple gases will be an important research direction in this field.
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