Sensors are evolving with the times, and their accuracy is constantly improving, leading to their increasingly widespread application in daily life. To enhance understanding of sensors, this article will introduce the characteristics and development of gas sensors. If you are interested in sensors, please continue reading.
I. Characteristics of Gas Sensors
1. Stability
Stability refers to the stability of a sensor's basic response throughout its operating time, depending on zero-point drift and range drift. Zero-point drift refers to the change in the sensor's output response during the entire operating time when the target gas is absent. Range drift refers to the change in the sensor's output response when continuously exposed to the target gas, manifested as a decrease in the sensor's output signal during the operating 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, and it primarily depends on the technology used in the sensor structure. Most gas sensors are designed using biochemical, electrochemical, physical, and optical principles. The first consideration is selecting a sensitive technology that is sufficiently sensitive to detect the percentage of the target gas's threshold value (TLV) or lower explosive limit (LEL).
3. Selectivity
Selectivity, also known as cross-sensitivity, 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 crucial in applications tracking multiple gases because cross-sensitivity reduces measurement repeatability and reliability; an ideal sensor should possess both high sensitivity and high selectivity.
4. Corrosion resistance
Corrosion resistance refers to the sensor's ability to withstand exposure to high volume fractions of target gas. In the event of a significant gas leak, the probe should be able to withstand 10 to 20 times the desired gas volume fraction. Upon returning to normal operating conditions, sensor drift and zero-point correction values should be as small as possible.
The fundamental characteristics of gas sensors, such as sensitivity, selectivity, and stability, are primarily determined by the selection of materials. Choosing appropriate materials and developing new materials are crucial for optimizing the sensitivity of gas sensors.
II. Development of Gas Sensors
(I) Focusing 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 C, C2H5OH, and CO. This research mainly focuses on two directions:
1. This involves using chemical modification methods to dope, modify, and surface-modify existing gas-sensitive membrane materials, and improving and optimizing the film formation process to enhance the stability and selectivity of gas sensors;
2. The research and development of new gas-sensitive membrane materials, such as composite and hybrid semiconductor gas-sensitive materials and polymer gas-sensitive materials, aims to enable these new materials to exhibit high sensitivity, high selectivity, and high stability to different gases. Organic polymer sensitive materials have become a research hotspot due to their advantages, including abundant material availability, low cost, simple film-forming process, easy compatibility with other technologies, and operation at room temperature.
(II) Development of Novel Gas Sensors
By utilizing traditional operating principles and certain novel effects, and prioritizing the use of crystalline materials (silicon, quartz, ceramics, etc.), advanced processing techniques, and microstructure design, novel sensors and sensor systems are being developed. Examples include the development and application of optical waveguide gas sensors, polymer surface acoustic wave sensors, and quartz resonant gas sensors, as well as research on microbial gas sensors and biomimetic gas sensors. With the application of new materials, processes, and technologies, the performance of gas sensors is becoming increasingly sophisticated, enabling miniaturization, microsizing, and multifunctionality with advantages such as long-term stability, ease of use, and low cost.
(III) Intelligent Gas Sensors
With the continuous improvement of people's living standards and increasing emphasis on environmental protection, higher demands are being placed on gas sensors for detecting various toxic and harmful gases, monitoring air pollution and industrial waste gases, and testing the quality of food and living environments. The successful application of new materials technologies such as nanotechnology and thin-film technology has provided excellent preconditions for the integration and intelligentization of gas sensors. Gas sensors will develop based on the comprehensive application of multidisciplinary technologies such as micromechanics and microelectronics, computer technology, signal processing technology, sensing technology, fault diagnosis technology, and intelligent technology. Developing fully automatic digital intelligent gas sensors capable of simultaneously monitoring multiple gases will be an important research direction in this field.
