Gas sensor classification and principle

Gas sensor overview:

Gas sensors are classified based on detection targets. Any sensor used to detect gas composition and concentration can be called a gas sensor. Because of the complexity of gas components, it is difficult to classify gas sensors very accurately. In terms of detection objects, the measurement objects of gas sensors include oxygen sensors (commonly used paramagnetic type, zirconia type), flammable and explosive gas sensors (commonly used catalytic combustion type, infrared, thermal conductivity, semiconductor type), toxic gas sensors (Generally using electrochemistry, metal semiconductor, photo ionization, flame ionization type), harmful gas sensors (often using infrared, ultraviolet, etc.) and organic volatile gas sensors, etc. According to different detection principles, mainstream gas sensors can be divided into semiconductor Category, catalytic combustion category, electrochemistry category, optical category, solid electrolyte category, etc.

Classification according to detection principle:

1. Semiconductor gas sensor

Semiconductor gas sensors appeared relatively early and are widely used in combustible gas leak detection and alarm devices in homes and factories. They are suitable for the detection of methane, liquefied gas, hydrogen and other gases. The advantages are high cost performance and simple design and manufacturing process; the shortcomings of semiconductor gas sensors are also very obvious. They are easily interfered by background gas and temperature, have large power consumption, poor stability and poor linearity during operation.

2. Catalytic gas sensor

This gas sensor is also suitable for the detection of methane, liquefied gas, hydrogen and other gases. Different from semiconductor gas sensors, catalytic combustion sensors use high-temperature resistant platinum layers to contact combustible gases and burn on their surfaces to detect the presence of combustible gases. Its advantages are accurate measurement, fast response, and long life; its disadvantages are that it is not selective for flammable gases, and there is a risk of ignition and explosion when working under dark fire.

3. Electrochemical gas sensor

Due to its early development time and high maturity, electrochemical technology has a high market share (nearly 60%). Countries such as the United Kingdom and Germany have established core positions in this field. There are two main types of gas sensors: subdivision sensors. The first potentiostatic electrolytic sensor is mainly used to detect toxic gases. The second type of galvanic cell gas sensor is mainly used to detect oxygen and has extremely high sensitivity.

Electrochemical gas sensors have the advantages of small size, low power consumption, and high sensitivity. However, they also have problems such as susceptibility to interference, short service life, and stability.

4. Optical gas sensor

There are three main types of optical sensors: Infrared gas sensor, photoreactive gas sensor, and optical fiber temperature sensor. The principle is to transmit signals through gas sensitivity and spectral response changes, and have high sensitivity to SO2, CO, CO2, NOx and other gases.

Due to the late development of the technology, the technical difficulty is high, but the measurement accuracy, anti-interference, service life and stability have been enhanced. The field has broad application prospects.

5. Solid electrolyte gas sensor

A solid electrolyte gas sensor is a chemical battery using an ionic conductor as the electrolyte. Through the cooperation of the electrolyte and the diaphragm, when gas is detected, a potential difference is generated in the electrolyte, and the gas information is converted into an electrical signal and output. Due to its high conductivity, good sensitivity and selectivity, this sensor has been widely used and has entered almost every field such as petrochemicals, environmental protection, and mining, second only to semiconductor gas sensors.