A Detailed Explanation of the Development, Technical Characteristics, Principles and Applications of Gas Sensors
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A Detailed Explanation of the Development, Technical Characteristics, Principles and Applications of Gas Sensors

Gas sensors have a wide range of applications and numerous types in our daily lives. From an automobile to a smart wristband, the sensors embedded in them all embody the crystallization of human wisdom.
Logical components, memory components and sensing components have long been the three core components of electronic systems side by side. The development from pressure measurement and mechanical measurement to electrical measurement has undergone numerous transformations, and now we have entered the sensor era—a historical evolution of electronic components. While the cloud concept has gained popularity and overshadowed some traditional components, sensor components have emerged as a dark horse and carved out a niche of their own.
A sensor is a detection device that can perceive the measured information and convert it into electrical signals or other required forms of output information in accordance with certain rules, so as to meet the requirements of information transmission, processing, storage, display, recording and control.
The national standard GB7665-87 defines a sensor as: "A device or apparatus that can sense a specified measured quantity and convert it into a usable signal in accordance with certain rules (mathematical function laws), usually composed of a sensitive element and a conversion element."
The China Internet of Things University-Enterprise Alliance holds that the existence and development of gas sensors have endowed objects with sensory capabilities such as touch, taste and smell, breathing life into them little by little. A sensor is defined in the New Webster's Dictionary as: "A device that receives power from one system and usually delivers it to another in a different form."
To obtain information from the outside world, humans must rely on their sensory organs. However, the functions of human sensory organs alone are far from sufficient in the study of natural phenomena and laws as well as in production activities. To adapt to this situation, sensors are indispensable. Therefore, it can be said that sensors are an extension of human's five sense organs, also known as the electronic five sense organs.
With the advent of new technologies, the world has entered the information age. In the process of utilizing information, the first thing to solve is to obtain accurate and reliable information, and sensors are the main way and means to acquire information in the natural and production fields.
In modern industrial production, especially in automated production processes, various sensors are used to monitor and control various parameters in the production process, ensuring that equipment operates in a normal or optimal state and products reach the highest quality standards. Therefore, it can be said that modern production would lose its foundation without a large number of high-quality sensors.
Sensors have long penetrated into an extremely wide range of fields such as industrial production, space exploration, marine detection, environmental protection, resource survey, medical diagnosis, bioengineering and even cultural relic protection. It is no exaggeration to say that almost every modern project, from the vast outer space to the boundless ocean, and even various complex engineering systems, is inseparable from various types of sensors.
It is evident that sensor technology plays an extremely prominent role in developing the economy and promoting social progress. Countries around the world attach great importance to the development of this field. It is believed that in the near future, sensor technology will achieve a leap forward and reach a new level commensurate with its important status.
A sensor is generally composed of four parts: a sensitive element, a conversion element, a conversion circuit and an auxiliary power supply, as shown in the figure below.
The sensitive element directly perceives the measured quantity and outputs a physical signal with a definite relationship to the measured quantity; the conversion element converts the physical signal output by the sensitive element into an electrical signal; the conversion circuit is responsible for amplifying and modulating the electrical signal output by the conversion element; the conversion element and the conversion circuit generally also need to be powered by an auxiliary power supply.

Technical Characteristics of Gas Sensors

China's sensor industry is in a critical stage of developing from traditional sensors to new-type sensors, which reflects the general development trend of new-type sensors toward miniaturization, multi-functionality, digitalization, intellectualization, systematization and networking. Sensor technology has undergone years of development, and its technological evolution can be roughly divided into three generations:
  1. Structural sensors, which sense and convert signals by virtue of changes in structural parameters.
  2. Solid-state sensors, developed in the 1970s. Composed of solid components such as semiconductors, dielectrics and magnetic materials, these sensors are manufactured by utilizing certain characteristics of materials. For example, thermocouple sensors, Hall sensors and photosensitive sensors are made by using the thermoelectric effect, Hall effect and photosensitive effect respectively.
  3. Intelligent sensors, the newly developed third generation of sensors, which are the product of the combination of microcomputer technology and detection technology, endowing sensors with a certain degree of artificial intelligence.