Sensors in environmental detection can be divided into gas sensors and liquid sensors, this is my sensor detection technology paper for everyone, just for reference!
Sensor Detection Technology Paper IAn attempt to describe the application of sensor technology in environmental detection
Abstract: Sensors in environmental detection can be divided into gas sensors and liquid sensors, of which gas sensors are mainly detected nitrogen oxides and sulfur-containing oxides; liquid sensors are mainly detected in the heavy metal ions, polycyclic aromatic hydrocarbons, pesticides, and biological sources of class. This paper describes the application of sensor technology in environmental detection.
Keywords: gas sensor, liquid sensor, environmental detection
Classification number: O659 Literature identification code: A Article number:
As people pay more attention to the quality of the environment, in the actual environmental testing, people usually need to be able to carry, but also can be enough to achieve a variety of to be measured by continuous dynamic monitoring of the instruments and analytical equipment. The new sensor technology is able to meet these needs.
Sensor technology consists of two main parts: the part that can react with the object to be measured and the signal converter part. The role of the signal converter is to react with the object to be measured after the changes through the electrical or optical signal representation. According to the different detection methods, we divide the sensors into optical sensors and electrochemical sensors; according to the different reaction principles, they are divided into immunosensors, enzyme biosensors, chemical sensors; according to the different detection objects, they are divided into liquid sensors and gas sensors.
1 gas sensors
Gas sensors can detect indoor air quality, especially polluted houses or hallways; can also detect pollutants in the atmospheric environment, such as sulfur-containing oxides, nitrogen oxides, and so on, the detection process quickly and easily.
Take nitrogen-containing oxides (NOx) as an example. Automobile exhaust is the main source of NOx, but with the development of the times, the domestic consumption level increases, the emissions of automobile exhaust is rising year by year. Direct detection of NOx-containing emissions from automobile exhaust and factory exhaust is performed by metal oxide semiconductors. Such as Dutta designed sensors, using platinum as the electrode, yttrium oxide and zirconium oxide as the oxygen ion converter, installed in the gas discharge port, can detect the content of 10-4 ~ 10-3 NO. Sulfur-containing oxides are the main substances that cause acid rain, but also the current focus of the environmental testing program, because the content of the atmospheric environment is lower than 10-6, the need for a higher sensitivity sensor. For example, surface acoustic wave devices with high detection sensitivity.
Starke et al. used a diameter of 8 ~ 16nm of tin oxide, indium oxide, tungsten oxide nanoparticles made of nanoparticle sensors, the lower limit of detection of NO and NO2 can reach 10-8, to improve the specific surface area of the reaction, to increase the sensitivity of the reaction, and the operating temperature is greatly reduced than conventional sensors, reducing energy consumption.
2 liquid sensors
In the actual environmental testing, liquid sensors are mostly used in water testing. Because of the wide range of pollutants in the water environment, liquid sensors are more widely used and important than gas sensors. In addition to a small number of natural pollutants in the water, most of the pollutants are man-made dumping of inorganic and organic matter. Among the inorganic substances, heavy metal ions are the key test objects; organic pollutants include pesticides, hormone metabolites, polycyclic aromatic hydrocarbons and other substances. Excessive excess of these pollutants can seriously affect the health and safety of all organisms.
2.1 Detection of heavy metal ions
The main sources of heavy metal ions in extracted waters include wastewater discharged by mining, metallurgy, printing and dyeing enterprises. These production wastewater is often mixed with a variety of wastewater, containing a wide range of heavy metal ions, common mercury, manganese, lead, cadmium, chromium and so on. Heavy metal ions will constantly undergo changes in form and transfer between different phases, and if not disposed of properly, secondary pollution is easily formed. Heavy metal ions ingested by organisms from the environment, through the food chain, are gradually enriched in higher organisms, eventually leading to poisoning of the organisms. Therefore, if the metal ions in fish for human consumption exceed the standard, it will have serious impact on human beings, so the detection of heavy metal ions is particularly important.
Burge et al. have invented a sensor that can utilize 1,2,2 biphenylcarbazide and a spectrophotometer, which can detect if the concentration of the heavy metal chromium in groundwater exceeds the standard.
In addition to detection by chemical reactions, the use of special biological substances can also be convenient and sensitive to detect heavy metal ions. For example, there is a protein in E. coli that can bind nickel ions, and some people have inserted a fluorescent group near the nickel ion binding site of this protein. when the protein binds nickel ions, the fluorescent group will be quenched, and since the intensity of the fluorescence is inversely proportional to the concentration of nickel ions, thus realizing quantitative detection of nickel ions, and the detection range has not been 10-8~10-2 mol/L. The method of the day can also be applied to the detection of Cu2 +, Co2+, Fe2+ and Cd2+ among several ions. They also incorporated microfluidic technology, which can detect Pb2+ at concentrations below 100 nmol/L by consuming only a few tens of nanoliters of the volume of liquid to be tested.Matsunaga's group immobilized TPPS in a porous silica matrix, and the color of the TPPS gradually shifted from orange to green as the concentration of Hg2+ changed in response to changes in the environment in the presence of Hg2+.The The detection limit of the sensor was 17.5 nmol/L, and the interfering ions Ni2+ and Zn2+ were removed by adding silica-aluminate.
The use of sensor technology can not only accurately determine the concentration of the substance to be measured, but also due to the miniaturization of the sensor technology characteristics, but also through the coupling of sensors, a number of indicators of the detection.Lau et al. designed a light-emitting diode principle based on the sensor can be detected at the same time as the Cd2+ and Pb2+, the detection limit of the sensor of the Cd2+ and Pb2+, respectively, for 10-6 and 10-8.
2.2 Detection of Pesticide Residues
Pesticides are a special class of chemicals, which, while controlling agricultural and forestry pests and diseases, can also cause serious harm to humans and animals. China is a large agricultural country, and the amount of pesticides used each year is quite huge, so it is necessary to monitor them. Triazine herbicides can be easily detected by using cobalt-benzenedimethylene blue dye and galvanometer without deoxygenation, and the lower limit of direct detection is 50 Lg/L, and the limit of detection can reach 200 ng/L if the sample is concentrated by pre-treatment.
Rapid detection of pesticides can be carried out by using infrared spectral sensors with optical fibers. After coating the inner wall of the optical fiber with aerosol material modified by non-polar organic matter, the signal dissipation effect of water molecules in the optical fiber can be significantly improved, and the organophosphorus insecticides in solution can be extracted for spectral analysis. The detection limit of such sensors for organic solvents such as benzene, toluene and xylene can be as high as 10-8~8*10-8.
2.3 Detection of polycyclic aromatic hydrocarbons (PAHs)
PAHs are another large group of hazardous pollutants that are carcinogenic, but are used or produced in many industrial processes. The very low levels of PAHs in water, typically in the 10-9 range, require the use of highly sensitive detection sensors, and Schechter's group invented a fiber-optic optical fluorescence sensor. In the direct detection process, to be tested in the sample there may also be some such as dirt such as interference substances, will reduce the detection signal value, if the polymer membrane will first be non-polar PAH enrichment, and then on the membrane of the material for fluorescence detection, so as to solve the problem of signal interference, reported that this by the membrane after the enrichment of the sensor technology, the detection of pyrene can be up to 6 * 10-11, anthracenes Stanley et al. used a quartz crystal microbalance as a sensor and fixed a single molecule membrane of anthracene-carbonate on the surface of the chip, and the detection limit could reach 2*10-9.
Based on the principle of immunoassay, molecular blotting is used to print antibody molecules on the sensor surface that are able to bind different substances to be tested, so that the detection of a wide range of different substances can be realized. The micro-contact printing technology developed in recent years can also be applied to this field, so that the size of the prepared sensor can be more miniaturized.
2.4 Biological Pollutants
In addition to the above inorganic and organic synthetic pollutants, there are also a number of potentially polluting molecules of biological origin. Hormones and their metabolites often cause abnormalities in the growth, development and reproduction of living organisms, and the research team led by Gauglitz used a total internal reflection fluorescent biosensor and testosterone antibodies to instantly detect testosterone directly in the river, with a limit of detection of 0.2 ng/L. The technique requires no sample pretreatment and can be used in natural water bodies in different regions. In addition, pathogenic bacteria and viruses are also detected. The presence of certain specific strains of bacteria in a water body can indicate that the water body has been contaminated in some way, and the presence of these organisms can be easily detected using the sensor technology, and the selectivity is very high, for example, plant viruses can be detected quickly from tobacco leaves. Tobacco mosaic virus, the use of QCM can be directly detected in the number of yeast cells.
3 Conclusions and Prospects
At present, sensor technology has begun to be applied to the emergency detection of various environmental monitoring organizations, but there are many limitations in the practical application, such as in the detection of certain hazardous substances in the atmosphere, because the content is often lower than the sensor's minimum detection limit, and therefore in the process of practical application, it is necessary to carry out a concentration of the gas, which makes the Sensors are not easy to achieve miniaturization, or the need to resort to higher sensitivity sensors; Similarly, in the field water detection, there will often be water to be measured contains a variety of complex interfering components of the situation, can not be compared with the standardized conditions of the laboratory; in some of the analytical technology based on the principle of membrane separation sensors, the service life of the membrane tends to be shorter, and frequent replacement of the price of new membranes is more expensive, and thus remains
These are the most important factors in the development of a new technology.
Nevertheless, with the continuous development and improvement of sensor technology, it is still expected to be applied to the future of the factory enterprise exhaust, sewage discharge on-site direct detection and dynamic unmanned monitoring of the field environment, and the results can be consistent with the results of the laboratory conventional instrumentation, which will greatly accelerate the pace of environmental monitoring and management.
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Sensor Detection Technology Thesis IISensor and Automatic Detection Technology Teaching Reform Discussion
Abstract: Sensor and automatic detection technology is an important backbone of the electrical information specialty professional courses. The traditional teaching method focuses on the teaching of theoretical knowledge, but ignores the training of the application level. In order to address this problem, we try to analyze the teaching purpose, teaching content, teaching form, teaching effect and other aspects of the teaching program reform of the course to discuss, put forward a set of skills and theoretical knowledge combined, effective teaching program.
Keywords: sensor and automatic detection technology; teaching content; teaching mode; engineering thinking
? Sensors and automatic detection technology? Is an important backbone of the electrical information specialties, is a compulsory course, but also a comprehensive technology involving electrical and electronic technology, sensor technology, photoelectric detection technology, control technology, computer technology, data processing technology, precision mechanical design technology and many other basic theories and technologies, modern detection systems are usually set of optical, mechanical, electrical in one, a combination of hardware and software.
? Sensors and automatic detection technology? Course in the 1980s began in China's general colleges and universities at the undergraduate level and graduate level. This course focuses on the teaching of the theory of sensors and automatic detection technology, heavy knowledge, light skills; teachers also lack of communication between the teaching resources can not be fully utilized, the teaching effect is not ideal, students are not interested in learning.
I. Problems found in the teaching process and the need for reform analysis
The author taught in independent colleges? Sensors and automatic detection technology? Course has been four years, the beginning of the teaching plan and syllabus along the research universities, as research universities are to cultivate research-oriented talents, and independent colleges are to cultivate application-oriented talents, there are large differences in the objectives of talent cultivation, in the process of gradual in-depth discovery of the traditional program is not quite in line with the college to cultivate the positioning of application-oriented talents, the existence of the following aspects of the problem.
1. Heavy theory, light practice
The course is an applied course, which also has a lot of theoretical knowledge, mathematical derivation, and the traditional research-based teaching methods are generally based on theoretical teaching, in the classroom to explain the principles of sensors, mathematical formulae derivation, compared to the application of sensors is usually just a simple introduction through an example, resulting in the end of the majority of the Students only roughly know the structure of the sensor, but do not know how to use, where to use.
2. Teaching mode single
The course is traditionally based on the teaching mode of lecture, the ready-made conclusions, formulas and theorems to tell students, students can not take the initiative to think and explore, the process of boring, leading to the students produce an aversion to learning. At the same time, the disconnection between theoretical teaching and practical training, practical teaching is also a serious problem.
3. Teaching experiment arrangement is unreasonable
The traditional experimental course arrangement, the proportion of validation experiments as high as 80%, comprehensive design experiments are very few, the lack of practical training, practical links. However, the training of applied talents should be based on practical teaching as the core, focusing on cultivating students' engineering thinking and practical ability, hands-on ability, in order to achieve the technical level and ability of the enterprise requirements at the time of graduation, so that students can adapt to the workplace as soon as possible after graduation.
Second, suitable for independent colleges and universities to cultivate applied talents of the teaching program reform
The traditional sensors and automatic detection technology courses focus on theory, light practice, a single mode of teaching, teaching experiments to verify the experiments are mainly, this program is able to cultivate research talents, but can not cultivate qualified applied talents. In the teaching process, the author studied, and repeated practice, summed up the following aspects can be reformed.
1. Optimize the teaching content, focus on engineering thinking
This course is a very important content is the principle of various types of sensors, the traditional teaching to make clear the ins and outs of which, and I believe that for the training of applied talents, fully teach the basic concepts, basic principles and basic methods can be involved in the large amount of mathematical formulas can be selected to explain the important, the other can be used as students' self-study content. The other can be used as the students' self-study content, so that students can study on their own after class. At the same time should focus on explaining the sensor engineering applications; on the other hand, it should be combined with the latest practical engineering explanations. This will stimulate students' interest in learning, and cultivate students' applied engineering learning thinking.
2. Reform teaching methods, change the teaching mode
Traditional teaching is ? The traditional teaching is the "indoctrination" method. The author believes that the application of engineering case teaching, the implementation of heuristic, discussion, research and other teaching methods combined with practice, play the main position of students in teaching activities.
3. Combined with the actual engineering, combined with other courses
The teaching process should be extracted from different industries typical engineering applications, streamlined as an example to explain. When teaching, we should cultivate the students' system view, so that students understand that this is not an independent course, but with the principles of automatic control, intelligent control theory and other courses are integrated to achieve a coherent learning effect.
4. Experimental reform
Experimental teaching is mainly to improve students' hands-on ability, the ability to analyze and solve problems, and deepen students' perceptual understanding of theories and concepts in classroom teaching. In the past, most of the experimental content of the course for the principle, verification of experiments, students are prone to feel boring, no learning enthusiasm, few students to think independently and find problems, the experimental effect is extremely unsatisfactory. In order to change this pattern of education, the author will adjust the experimental content from the traditional verification experiments to design and development experiments. In the experimental teaching according to the objective conditions in the appropriate reduction of verification experiments on the basis of an increase in pioneering experimental projects as well as the design of comprehensive experiments.
5. Reform teaching evaluation methods, improve classroom teaching efficiency
Efficient learning results feedback mechanism is a necessary means to promote the growth of teaching and learning, the course is currently through the course work for learning results feedback, can be used in each chapter to arrange a design-type questions, so that students more extensive access to information, and in a certain breadth of knowledge on the basis of in-depth analysis of the topic of The content used, and then from a deeper level of analysis to solve the problem, in order to achieve a combination of depth and breadth of the effect.
This paper addresses the traditional research university program of sensors and automatic detection technology, puts forward three aspects of the problem, and according to four years of teaching accumulation, in the teaching content, teaching mode, experimental links, teaching evaluation and feedback, etc. several aspects of the discussion and analysis and puts forward a set of reform methods and measures. This program is based on practical engineering applications as the core, focusing on the application of sensors in the teaching content of the explanation to raise the issue, analyze the problem, solve the problem as the main line to mobilize the students' learning enthusiasm and initiative, to train students' engineering thinking and ability to pay attention to the experimental aspects of the design, comprehensive experiments instead of validation experiments to train the students to make the abstract knowledge concrete, to train the students' practical application ability, the hands-on ability and innovation ability. The experimental link is emphasized.
References:
[1] Wu Jianping, Gan Yuan. Sensor? Research on experimental teaching of the course[J]. Journal of Chengdu University of Technology.
[2]Cao Liangyu, Zhao Tangchun. Sensor technology and its application. A preliminary study of curriculum reform[J]. China Modern Educational Equipment.
[3]Li Yuhua, Hu Xuemei. Sensors and Applications. Exploration of course teaching reform Ⅱ technology and market.