Gas detector semiconductor type
　　
It is manufactured using the principle that the conductivity of some metal oxide semiconductor materials changes with the composition of the ambient gas at a certain temperature. For example, an alcohol sensor is prepared based on the principle that when tin dioxide encounters alcohol gas at high temperatures, its resistance will sharply decrease.
　　
Advantages: Semiconductor gas sensors can be effectively used for detecting many gases such as methane, ethane, propane, butane, alcohol, formaldehyde, carbon monoxide, carbon dioxide, ethylene, acetylene, vinyl chloride, styrene, acrylic acid, etc. Especially, this type of sensor is low-cost and suitable for the needs of civilian gas detection. The following semiconductor gas sensors are successful: methane (natural gas, biogas), alcohol, carbon monoxide (city gas), hydrogen sulfide, ammonia (including amines and hydrazine). High quality sensors can meet the needs of industrial testing. Industrial Scientific, American gas sensor
　　
Disadvantages: Poor stability and significant environmental impact; Especially, the selectivity of each sensor is not *, and the output parameters cannot be determined. Therefore, it is not suitable for places that require accurate measurement.
　　
Gas detector combustion type
　　
This type of sensor is prepared with a high-temperature resistant catalyst layer on the surface of a platinum resistor. At a certain temperature, combustible gases catalyze combustion on its surface. Combustion is a function of the concentration of combustible gases as the temperature of the platinum resistor increases and the resistance changes.
　　
Advantages: Catalytic combustion gas sensors selectively detect flammable gases: the sensor has no response to anything that cannot be burned. Catalytic combustion gas sensors have accurate measurement, fast response, and long lifespan. The output of sensors is directly related to the explosion hazard of the environment and is a dominant type of sensor in the field of safety detection.
　　
Disadvantage: No selectivity within the flammable gas range. Working in a dark environment poses a risk of ignition and explosion. Most organic elements have a toxic effect on sensors.
　　
Gas detector thermal conductivity pool type
　　
Each gas has its own specific thermal conductivity, and when there is a significant difference in thermal conductivity between two or more gases, a thermal conductivity element can be used to distinguish the content of one component. This type of sensor has been widely used for detecting hydrogen, carbon dioxide, and high concentration methane. This gas sensor has a narrow application range and many limiting factors.
　　
Gas detector electrochemical type
　　
A significant portion of its flammable, toxic, and harmful gases have electrochemical activity and can be electrochemically oxidized or reduced. By utilizing these reactions, gas composition can be distinguished and gas concentration can be detected. Electrochemical gas sensors are divided into many subcategories:
　　
(1) The principle of the original battery type gas sensor (also known as the Cavani battery type gas sensor, fuel cell type gas sensor, or spontaneous battery type gas sensor) is the same as the dry battery we use, except that the carbon manganese electrode of the battery is replaced by a gas electrode
　　
That's it. Taking an oxygen sensor as an example, oxygen is reduced at the cathode, and electrons flow through an ammeter to the anode, where lead metal is oxidized. The magnitude of the current is directly related to the concentration of oxygen. This type of sensor can effectively detect oxygen, sulfur dioxide, chlorine gas, etc.
　　
(2) Constant potential electrolytic cell type gas sensor, which is very effective for detecting reducing gases. Its principle is different from the original battery type sensor, and its electrochemical reaction occurs under the force of current. It is a true Coulomb analysis sensor. This type of sensor has been successfully used in the detection of gases such as carbon monoxide, hydrogen sulfide, hydrogen, ammonia, hydrazine, etc. It is currently the mainstream sensor for detecting toxic and harmful gases.
　　
(3) The concentration battery type gas sensor, with electrochemically active gas on both sides of the electrochemical cell, will spontaneously form a concentration electromotive force, and the magnitude of the electromotive force is related to the concentration of the gas. Successful examples of such sensors are oxygen sensors for automobiles and solid electrolyte type carbon dioxide sensors.
　　
(4) Extreme current gas sensor is a type of sensor that measures oxygen concentration. It uses the principle that the extreme current in the electrochemical cell is related to the carrier concentration to prepare an oxygen (gas) concentration sensor, which is used for oxygen detection in automobiles and oxygen concentration detection in molten steel.
　　
Gas detector infrared
　　
Most gases have characteristic absorption peaks in the mid infrared region. By detecting the absorption situation of the characteristic absorption peak position, the concentration of a certain gas can be determined.
　　
This type of sensor used to be a large analytical instrument, but in recent years, with the development of the sensor industry based on MEMS technology, the volume of this sensor has decreased from a giant of 10 liters and 45 kilograms to around 2 milliliters (thumb size). The use of infrared detectors that do not require modulation of the light source enables the instrument to have no mechanical moving parts and achieve maintenance free operation. Infrared gas sensors can effectively distinguish the types of gases and accurately measure gas concentrations. This sensor has been successfully used for the detection of carbon dioxide and methane.
　　
Nanjing Huanan Intelligent Technology Co., Ltd. is a high-tech enterprise that integrates the research and development, production, and sales of intelligent instruments and meters. The company's development direction is to achieve remote monitoring of traditional detection and analysis instruments through the Internet of Things.
　　
Since its establishment, the company has completed the development and testing of remote monitoring systems for chemical testing instruments, remote monitoring systems for oil fume detection, and wireless local monitoring systems for pesticide detection in grain and tobacco depots, which have been recognized by society and relevant personnel.