Sensor detection principle of gas detection alarm

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Sensor detection principle of gas detection alarmThe concentration of gas detection depends on the gas detection transmitter. Sensors are its core components. According to different detection principles, it is mainly divided into metal oxide semiconductor sensors, catalytic combustion sensors, constant potential electrolytic gas sensors, gas sensors, etc. Varney battery oxygen sensor, infrared sensor, PID photoionization sensor, etc. Below is a brief summary of the principles and characteristics of various sensors.

A. Metal oxide semiconductor sensor

Metal oxide semiconductor sensors use the adsorption effect of the measured gas to change the conductivity of the semiconductor, and activate the alarm circuit by comparing the current changes. Due to the significant environmental impact during the measurement process of semiconductor sensors, the output linearity is unstable. Metal oxide semiconductor sensors are highly sensitive and are therefore widely used in the field of gas leak measurement.

B. Catalytic combustion sensor

The principle of catalytic combustion sensor is one of the most widely used principles for detecting combustible gases. It has the characteristics of good output signal linearity, reliable indicators, low price, and no cross interference with other non combustible gases. The catalytic combustion sensor adopts the Wheatstone bridge principle, where the sensing resistor and combustible gases in the environment undergo flameless combustion, causing the temperature to change the resistance value of the sensing resistor, breaking the balance of the bridge and outputting a stable current signal. The amplification, stabilization, and processing of the later circuit ultimately display reliable values.

c. Constant potential electrolytic gas sensor

Constant potential electrolytic sensor is currently the most widely used technology in the field of drug detection. In this regard, foreign technology is in a position, so most of these sensors rely on imports. The structure of a constant potential electrolytic gas sensor: In a cylindrical battery made of plastic, a working electrode, a counter electrode, and a reference electrode are installed, and an electrolyte is filled between the electrodes. The diaphragm is made of porous tetrafluoroethylene. *Package. The connection between the preamplifier and the sensor electrode applies a certain potential between the electrodes to keep the sensor in working condition. The gas in the electrolyte undergoes oxidation or reduction reactions with the working electrode, and then undergoes reduction or oxidation reactions with the counter electrode. The equilibrium potential of the electrode changes, and the change value is proportional to the gas concentration.

d. Gavari battery oxygen sensor

Structure of diaphragm type gastrointestinal oxygen sensor: Install a 10-30 μ m thick PTFE breathable membrane with good oxygen permeability on one side of the plastic container, with precious metal (platinum) tightly attached to the inside of the container The cathode is made of materials such as gold or silver, and the anode is formed on the other side of the container or in the empty part of the container (metals with a high tendency to ionize with lead or cadmium). Use potassium hydroxide. When oxygen passes through the electrolyte, an oxidation-reduction reaction occurs between the anode and cathode, causing the anode metal to ionize and release electrons. The current is proportional to the amount of oxygen. Due to the consumption of anode metal throughout the entire reaction process, sensors need to be replaced regularly. At present, domestic technology is becoming increasingly mature, and this type of sensor can be produced domestically.

e. Infrared sensor

Infrared sensors utilize the absorption principle of various elements at a certain wavelength, with good anti toxicity and sensitive response, and can react to most hydrocarbons. But the structure is complex and the cost is high.

f. PID photoionization gas sensor

PID consists of main components such as ultraviolet light source and ion chamber. There are positive and negative electrodes inside the ion chamber, forming an electric field. Under the irradiation of ultraviolet lamp, the measured gas is ionized to produce positive and negative ions, forming an electric current between the electrodes. The amplified output signal. PID has the advantages of high sensitivity, no toxicity issues, and reliability.