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The detection of gas concentration relies on gas detection transmitters, with sensors being their core component. Based on different detection principles, these sensors are mainly classified into metal oxide semiconductor sensors, catalytic combustion sensors, potentiometric electrolytic gas sensors, Galvanic cell oxygen sensors, infrared sensors, PID photoionization sensors, etc. The principles and characteristics of each type of sensor are briefly explained below. Metal oxide semiconductor sensors utilize the adsorption of the gas being measured to change the conductivity of the semiconductor; by comparing changes in current, an alarm circuit is activated. Since semiconductor sensors are highly affected by the environment during measurement, their output linearity is unstable. Metal oxide semiconductor sensors are widely used today for detecting minor gas leaks, thanks to their high sensitivity. Catalytic combustion sensors: The principle behind catalytic combustion sensors is one of the most widely used methods for detecting combustible gases. These sensors feature a linear output signal, high reliability, low cost, and no cross-interference with other non-combustible gases. Catalytic combustion sensors utilize the Wheatstone bridge principle; the sensing resistor undergoes flameless combustion with combustible gases in the environment, which causes a change in the resistance value of the sensing resistor and disrupts the balance of the bridge. This results in the generation of a stable current signal, which is then amplified, stabilized, and processed by subsequent circuitry to ultimately produce reliable numerical values. Potentiostatic electrolytic gas sensors: Potentiostatic electrolytic sensors are currently the most widely used technology for detecting toxins in field applications. Foreign countries lead in this area, which is why such sensors are mostly imported. Structure of the potentiostatic electrolytic gas sensor: Inside a plastic tubular cell, a working electrode, a counter electrode, and a reference electrode are installed; an electrolyte fills the space between these electrodes, and a diaphragm made of porous tetrafluoroethylene seals the top of the cell. The connection between the preamplifier and the sensor electrodes applies a certain potential between them, putting the sensor into operation. The gas undergoes oxidation or reduction reactions at the working electrode in the electrolyte, and oxidation or reduction reactions occur at the counter electrode; as a result, the equilibrium potential of the electrodes changes, with the magnitude of this change being proportional to the gas concentration. Structure of the diaphragm-type Galvanic cell oxygen sensor: On one side of the plastic container, there is a polytetrafluoroethylene gas-permeable membrane with a thickness of 10–30 μm, which allows oxygen to pass through easily. On the inner side of this container, a noble metal electrode (such as platinum, gold, or silver) is attached closely. The anode is formed on the inner side of the other side of the container or in the remaining space within the container; it is made of metals with a high tendency to ionize, such as lead or cadmium. Use potassium hydroxide. As oxygen passes through the electrolyte, redox reactions occur at the anode and cathode, causing the metal at the anode to ionize and releasing electrons. The magnitude of the current is proportional to the amount of oxygen present. Since the metal at the anode is consumed in this process, the sensor needs to be replaced regularly. Currently, domestic technology has become increasingly mature, allowing such sensors to be fully produced domestically. Infrared sensors utilize the principle of absorption by various elements at specific wavelengths; they have good resistance to poisoning, are highly sensitive, and can detect most hydrocarbons. But it has a complex structure and high costs. The PID photoionization gas sensor consists of main components such as an ultraviolet light source and an ion chamber. The ion chamber has positive and negative electrodes that create an electric field; when the gas to be measured is exposed to the ultraviolet light, it gets ionized, producing positive and negative ions. This results in the formation of an electric current between the electrodes, which is then amplified to generate a signal. PID has advantages such as high sensitivity, no poisoning issues, and safety and reliability.