Characteristics and future trends of gas sensors
Release time：
24 Feb,2022
Summary
Gas Sensor
I. Main Characteristics
Gas sensors are a major category of chemical sensors. From working principles and characteristic analysis to measurement techniques, from materials used to manufacturing processes, from detection objects to application fields, independent classification standards can be formed, giving rise to numerous and complex classification systems. Especially regarding classification standards, there is currently no unified standard, making it quite difficult to perform strict systematic classification.
1. Stability
Stability refers to the stability of the basic response of the sensor throughout its working time, depending on zero-point drift and range drift. Zero-point drift refers to the change in the sensor's output response over the entire working time in the absence of the target gas. Range drift refers to the change in the output response of the sensor continuously placed in the target gas, manifested as a decrease in the sensor's output signal over the working time. Ideally, a sensor should have a zero-point drift of less than 10% per year under continuous operating conditions.
2. Sensitivity
Sensitivity refers to the ratio of the change in sensor output to the change in the measured input, mainly depending on the technology used in the sensor structure. The design principles of most gas sensors employ biochemical, electrochemical, physical, and optical methods. The first consideration is to choose a sensitive technology that has sufficient sensitivity to detect the percentage of the threshold limit value (TLV) or lower explosive limit (LEL) of the target gas.
3. Selectivity
Selectivity is also known as cross-sensitivity. It can be determined by measuring the sensor response produced by a certain concentration of interfering gas. This response is equivalent to the sensor response produced by a certain concentration of the target gas. This characteristic is very important in applications tracking multiple gases, as cross-sensitivity reduces the reproducibility and reliability of measurements. An ideal sensor should have high sensitivity and high selectivity.
4. Corrosion Resistance
Corrosion resistance refers to the sensor's ability to withstand exposure to high volume fraction target gases. In the event of a large gas leak, the probe should be able to withstand 10 to 20 times the expected gas volume fraction. Upon returning to normal operating conditions, sensor drift and zero-point correction values should be as small as possible. The basic characteristics of gas sensors, namely sensitivity, selectivity, and stability, are mainly determined by the choice of materials. Selecting appropriate materials and developing new materials allows for optimizing the sensitive characteristics of gas sensors.
II. Future Trends
1. Focus on the research and development of new gas-sensitive materials and manufacturing processes
Research on gas sensor materials shows that metal oxide semiconductor materials such as ZnO, SiO2, and Fe2O3 have matured, especially in the detection of gases such as CO, C2H5OH, and CO. This work mainly focuses on two directions:
One is to use chemical modification methods to perform doping, modification, and surface modification on existing gas-sensitive membrane materials, and to improve and optimize the film-forming process to improve the stability and selectivity of gas sensors; the other is to develop new gas-sensitive membrane materials, such as composite and mixed semiconductor gas-sensitive materials and polymer gas-sensitive materials, so that these new materials have high sensitivity, high selectivity, and high stability for different gases. Due to the advantages of abundant materials, low cost, simple film-forming process, easy compatibility with other technologies, and operation at room temperature, organic polymer sensitive materials have become a research hotspot.
2. Development of new gas sensors
Using traditional working principles and some new effects, prioritizing crystalline materials (silicon, quartz, ceramics, etc.), and employing advanced processing techniques and microstructure design, new sensors and sensor systems are being developed, such as optical waveguide gas sensors, the development and use of polymer surface acoustic wave and quartz crystal resonator gas sensors, and the research of microbial gas sensors and biomimetic gas sensors. With the application of new materials, new processes, and new technologies, the performance of gas sensors is becoming more perfect, making miniaturization, microminiaturization, and multi-functionalization of sensors have advantages such as good long-term stability, ease of use, and low cost.
3. Intelligent gas sensors
With the continuous improvement of people's living standards and increasing attention to environmental protection, the detection of various toxic and harmful gases, the monitoring of air pollution and industrial waste gas, and the detection of food and residential environment quality have put forward higher requirements for gas sensors. The successful application of new material development technologies such as nano and thin film technologies has provided good prerequisites for the integration and intelligence of gas sensors.
Gas sensors will be developed based on the comprehensive application of multidisciplinary technologies such as micro-mechanical and microelectronic technology, 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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