According to the national standard GB7665-87, a sensor is a device or apparatus that can sense a specified measured quantity and convert it into an available output signal. Gas sensors, as an important branch, specifically refer to devices that detect gas components and concentrations. The classification is based on the detection target and is independent of the detection method. It should be noted that gas flow sensors do not fall into this category, but thermal conductivity gas analyzers, due to their core function being gas detection, still belong to gas sensors.
Since the 1970s, gas sensors have developed into a major system in the field of sensors, belonging to chemical sensors. Currently, the mainstream gas sensors in the market are divided into 7 categories, with the following core characteristics:
The core principle is to utilize the characteristic that the electrical conductivity of metal oxide semiconductor materials changes with the environmental gas components at a specific temperature. A typical example is an alcohol sensor, which is prepared by using the characteristic that the resistance of tin dioxide decreases dramatically when encountering alcohol.
They have a wide range of applications, can detect various gases such as methane, alcohol, and carbon monoxide, and are suitable for both civilian and industrial detection. The advantage is low cost. The disadvantages are poor stability, weak selectivity, and inaccurate output parameters, which are not suitable for high-precision measurement scenarios.
This sensor was invented in Japan and the main suppliers are Japan, China, and South Korea. The United States is not yet a mainstream. Domestic products, due to early policy and information factors, have inferior performance compared to Japan. They are expected to achieve breakthroughs through the market and private capital in the future.
The core structure is to prepare a catalyst layer on the surface of a platinum resistor, and combustible gases on its surface through catalytic combustion, causing the resistance to change with the concentration, thereby detecting the gas concentration.
The advantage is accurate measurement, fast response, long lifespan, and direct relevance to environmental explosion hazards. They dominate in the safety detection field and mainly detect combustible gases.
The disadvantage is that there is no selectivity within the range of combustible gases, and there is an explosion risk when working with a spark, and they are prone to poisoning by organic vapor elements.
It was invented by the United Kingdom, and the main suppliers are China, Japan, and the United Kingdom. China is the largest user and has mastered the production technology, and it is the mainstream manufacturing base for this type of sensor.
Based on the characteristic of gas thermal conductivity, they can distinguish gas components with significant thermal conductivity differences, and belong to old products. They are mainly used for hydrogen, carbon dioxide, and high-concentration methane detection, and have a narrow application range.
There are manufacturers worldwide, and the product quality varies little, with no significant technical barriers.
They detect through the electrochemical activity of combustible and toxic gases. They are divided into 4 types:
They determine the type and concentration of gases by detecting the characteristic absorption peaks of infrared in the gas, and are miniaturized through MEMS technology, without mechanical components and requiring no maintenance.
They are mainly used for carbon dioxide and methane detection, and the suppliers are concentrated in Europe. There is still a gap in this field in China.
They are prepared using the characteristic that oxygen can be attracted by a strong magnetic field, only detecting oxygen, with strong selectivity and minimal interference.
It is an old industrial product, and there are manufacturers worldwide. In recent years, it has gradually evolved into a pure sensor form.
PID detectors are more suitable to be classified as detection instruments because they cannot be maintained without maintenance; optical fiber sensors have developed rapidly and have great potential. It should be noted that some merchants exaggerate performance and confuse classifications, which is not conducive to user selection.
