science and technology limited company for you to share:Detection principle of several gas sensors

Contains the following gas sensors:
Metal Oxide Semiconductor Sensor
catalytic combustion gas sensor
constant potential electrolytic gas sensor
Gavani battery type oxygen sensor
Infrared Sensor
PID light ion gas sensor

The concentration of the detected gas depends on the gas detection transmitter, and the sensor is its core part. According to the different detection principles, it is mainly divided into metal oxide semiconductor sensors, catalytic combustion sensors, constant potential electrolytic gas sensors, Gavani battery oxygen sensors, infrared sensors, PID photoionization sensors, etc. The following briefly describes the principles and characteristics of various sensors.

metal oxide semiconductor sensor

The metal oxide semiconductor sensor uses the adsorption of the measured gas to change the conductivity of the semiconductor, and excites the alarm circuit by comparing the current changes. Because the semiconductor sensor is greatly affected by the environment, the output linear is unstable. Metal oxide semiconductor sensor, because of its very sensitive response, it is widely used in the field of measuring gas micro-leakage phenomenon.

catalytic combustion type sensor

The principle of catalytic combustion sensor is one of the widely used principles for detecting combustible gases. It has the characteristics of good output signal line shape, reliable index, low price, and no cross interference with other non-combustible gases. The catalytic combustion sensor adopts the Wheatstone bridge principle. The sensing resistor and the combustible gas in the environment burn without flame, so that the temperature changes the resistance of the sensing resistor, breaks the bridge balance, and makes it output a stable current signal. The amplification, stabilization and processing of the circuit finally display a reliable value.

constant potential electrolytic gas sensor

The constant potential electrolytic sensor is a kind of technology widely used in the field of measuring poison at present. In this respect, foreign technology is ahead, so most of these sensors rely on imports. The structure of the constant potential electrolytic gas sensor: in a cylindrical cell made of plastic, the working electrode, the counter electrode and the reference electrode are installed, and the electrolyte is filled between the electrodes. The diaphragm made of porous tetrafluoroethylene is packaged on the top. The preamplifier is connected to the sensor electrodes, and a certain potential is applied between the electrodes to make the sensor in a working state. The gas and the working electrode in the electrolyte are oxidized or reduced, and the electrode is reduced or oxidized, and the equilibrium potential of the electrode changes, and the change value is proportional to the gas concentration.

Gavani battery type oxygen sensor

The structure of the diaphragm Gavani battery oxygen sensor: a polytetrafluoroethylene breathable film with a thickness of 10 ~ 30μm and good oxygen permeability is installed on one side of the plastic container, a cathode electrode of precious metal (platinum, gold, silver, etc.) is tightly adhered to the inside of the container, and an anode (metal with high plasma tendency of lead and cadmium) is formed on the inside of the other side of the container or the spare part of the container. With potassium hydroxide. When oxygen passes through the electrolyte, an oxidation-reduction reaction occurs at the cathode and anode, ionizing the anode metal and releasing electrons. The size of the current is proportional to the amount of oxygen. As the anode metal is consumed in the whole reaction, the sensor needs to be replaced regularly. At present, the domestic technology has become increasingly mature, can be localized such sensors.

infrared sensor

The infrared sensor uses the absorption principle of various elements to a specific wavelength, has good anti-poisoning, sensitive response, and reacts to most hydrocarbons. But the structure is complex and the cost is high.

PID Photoionization Gas Sensor

PID is composed of ultraviolet light source and ion chamber and other major parts, in the ion chamber has positive and negative electrodes, the formation of electric field, the gas to be measured in the ultraviolet lamp irradiation, ionization, the generation of positive and negative ions, the formation of current between the electrodes, the amplified output signal. PID has the advantages of high sensitivity, no poisoning problems, safety and reliability.

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