A gas sensor is a sensor device that detects the presence of a specific gas in a certain range or continuously measures the gas composition. However, it is a very common way to monitor pollution in the industrial and living environment by using gas sensors.

Gas sensors are currently widely used in coal mines, chemical industry, agriculture, municipal administration, medical treatment and other aspects that require protection, and are often used to detect flammable, combustible and toxic gases, or to detect oxygen consumption. In some power companies and manufacturing industries, gas sensors are also commonly used to quantitatively detect the concentration of various components in the flue gas to determine harmful gas emissions and combustion conditions.

First, the characteristics of the gas sensor

1. Sensitivity

The sensitivity of a gas sensor refers to the ratio of the change in sensor output to the measured change.

2. Corrosion resistance

The corrosion resistance of a gas sensor refers to the ability of the sensor to be exposed to a high volume fraction of target gas. When encountering a large amount of toxic gas, the monitoring probe of the sensor will be corroded by the toxic gas. It is required that when the gas sensor faces such a large amount of toxic gas, when it returns to normal working conditions, the use error of the sensor is more likely to be low. If there is a large amount of gas leakage, the sensor probe can withstand the gas volume within 20 times. In a normal working environment, the drift positive correction value of the sensor should be as small as possible.

Second, the classification of gas sensors

Gas sensors can be divided into different types according to different detection standards.

Classified by testing standards

1. According to the different types of detected gases, it is divided into combustible gas sensors, toxic gas sensors, harmful gas sensors, and so on.

2. According to the installation and use method of the gas sensor, it can be divided into portable sensors and fixed sensors.

3. According to the method of obtaining the monitored gas, the sensors can be divided into diffusion sensors and suction sensors.

4. According to the detection principle of gas sensors, the gas sensors are divided into thermal sensors, electrochemical sensors, magnetic gas sensors, optical lift sensors and semiconductor gas sensors, gas chromatography sensors and so on.

Thirdly. Commonly used gas detection methods

At this stage, the most frequently used sensors are divided into semiconductor gas sensors and electrochemical sensors.

1. Semiconductor gas sensor

Semiconductor gas sensors can detect flammable gases with a relatively high concentration, and can also detect toxic and harmful gases with a relatively high PPM level. The advantages of this type of sensor are mainly high sensitivity and fast response, but at the same time it has the shortcomings of small measurable range and easy to be affected by the environment.

2. Electrochemical gas sensor

At present, the more common and mature sensor type for detecting toxic and harmful gases in chemical pollution is the electrochemical sensor. Although electrochemical gas sensors are susceptible to interference, they are greatly affected by changes in air temperature. However, due to its high sensitivity and high stability, this type of sensor can be used in the measurement of sulfuric acid, air separation and boiler combustion, and is therefore widely used.

Fourth, the types of gas sensor monitoring

1. Toxic gases include methane, hydrogen sulfide, carbon monoxide, carbon dioxide, hydrogen cyanide, etc. These gases can cause harm to the internal organs of the human body through the respiratory organs, and also inhibit the oxygen exchange ability of the internal tissues or cells of the human body, causing the body tissues Asphyxiating poisoning occurs due to lack of oxygen, so it is also called asphyxiant gas.

2. Corrosive gases are generally disinfection gases such as chlorine, ozone gas, chlorine dioxide gas, etc., when they are leaking, they will corrode the human respiratory system and cause poisoning.

3. When the flammable and explosive gas mixes with the air to a certain ratio, it will cause burning or even explosion when it encounters an open flame, which will cause harm. Such as methane, hydrogen, etc.