Industrial gas sensors

With the development of the petrochemical industry, the types and application ranges of flammable, explosive and toxic gases have increased. Once these gases leak during production, transportation, and use, they will cause poisoning, fire or even explosion accidents, seriously endangering people’s lives and property safety. Due to the diffusivity of the gas itself, after a leak occurs, the gas will diffuse along the ground surface under the action of external wind force and internal concentration gradient, forming a combustion, explosion or poisoning danger zone at the accident site, and expanding the hazard area.

Industrial gas sensors types

Foreign countries began to research and develop gas sensors in the 1930s. In the past, Industrial gas sensors were mainly used for the detection and alarm of coal gas, liquefied petroleum gas, natural gas and gas in mines. Currently, the types of gases that need to be detected have expanded from the original reducing gases (H2, C4H10, CH4) to toxic gases ( CO, NO2, H2S, NO, NH3, PH3), etc.

There are many types of industrial gas sensors. According to the gas-sensitive materials used and gas-sensing characteristics, they can be divided into semiconductor type, solid electrolyte type, electrochemical type, contact combustion type, polymer type, etc.

SemiconductorIndustrial gas sensor

This sensor mainly uses semiconductor gas-sensitive materials. Since the advent of semiconductor metal oxide gas sensors in 1962, they have been widely used due to their advantages such as high sensitivity and fast response. They have now become one of the most produced and widely used sensors in the world. According to the different ways of detecting gas-sensitive characteristic quantities, it is divided into two types: resistive type and non-resistive type.

1.The resistive semiconductor gas sensor works by detecting changes in the gas sensor as the gas content changes. Metal oxide ceramic gas-sensitive materials are mainly used. With the research and development of new materials such as composite metal oxides and mixed metal oxides in recent years, the characteristics and application range of this gas sensor have been greatly improved.

2.Non-resistive semiconductor gas sensors work based on the principle that the current or voltage of the gas sensor changes with the gas content. There are mainly MOS diode type, junction diode type, and field effect tube type gas sensors. Most of the detected gases are flammable gases such as hydrogen and silane.

Solid electrolyte Industrial gas sensor

Solid electrolyte gas sensors use solid electrolyte gas sensing materials as gas sensing elements. The principle is that the gas-sensitive material generates ions when passing through the gas, thereby forming an electromotive force, and the electromotive force is measured to measure the gas concentration. Due to its high conductivity, good sensitivity and selectivity, this sensor has been widely used and has entered almost every field such as petrochemical, environmental protection, mining, etc., second only to metal oxide semiconductor gas sensors.

Contact combustion type industrial gas sensor

It can be divided into two types: direct contact combustion type and catalytic contact combustion type. Its working principle is: when the gas-sensitive material is energized, the flammable gas oxidizes and burns or oxidizes and burns under the action of a catalyst. The heat generated heats the electric heating wire, thereby changing its resistance value. The resistance change is measured to measure the gas concentration. This sensor can only measure combustible gases and is insensitive to non-flammable gases. For example, sensors made by coating active catalysts Rh and Pd on Pt wire have broad-spectrum characteristics and can detect various combustible gases. Contact combustion gas sensors are very stable at ambient temperature and can detect most flammable gases at the lower explosion limit. They are widely used in petrochemical plants, shipyards, mine tunnels, bathrooms, kitchens, etc. to detect flammable gases. Monitoring and alarming.

Polymer Industrial gas sensor

Industrial gas sensors using polymer gas-sensitive materials have developed greatly in recent years. When polymer gas-sensitive materials encounter specific gases, their physical properties such as resistance, dielectric constant, material surface acoustic wave propagation speed and frequency, and material weight change. Mainly include phthalocyanine polymer, LB film, phenycyanine acetylene, polyvinyl alcohol-phosphoric acid, polyisobutylene, aminoundecylsilane, etc. Polymer gas-sensitive materials play an important role in the detection of toxic gases and food freshness due to their easy operability, simple process, good room temperature selectivity, low price, and easy combination with microstructure sensors and surface acoustic wave devices. . According to the gas-sensitive characteristics of the materials used, this type of sensor can be divided into: polymer resistance gas sensors that measure gas concentration by measuring the resistance of the gas-sensitive material; based on the concentration difference battery formed when the gas-sensitive material absorbs gas, and the electromotive force is measured to determine Concentration difference battery gas sensor of gas concentration; surface acoustic wave gas sensor based on the principle that the propagation speed or frequency of sound waves on the surface of the material changes after the polymer gas-sensitive material absorbs the gas; and the surface acoustic wave gas sensor based on the principle that the polymer gas-sensitive material absorbs the gas. Quartz oscillator type gas sensors made of weight changes, etc. Polymer gas sensors have high sensitivity to specific gas molecules, good selectivity, and simple structure. They can be used at room temperature and can supplement the shortcomings of other gas sensors.