The working principle of electrochemical gas sensor: the gas to be detected enters the sensor room after dust removal and dehumidification, and enters the electrolytic cell through the permeable membrane, so that the gas diffused and adsorbed in the electrolyte is electrolyzed at a specified oxidation potential, and its gas concentration is calculated according to the consumed electrolytic current.
A working electrode, a counter electrode and a reference electrode are installed in a cylindrical battery made of plastic, electrolyte is filled between the electrodes, and a diaphragm made of porous tetrafluoroethylene is encapsulated at the top. The connection between the preamplifier and the sensor electrode applies a certain potential between the electrodes, which makes the sensor in working state. The gas in the electrolyte undergoes oxidation or reduction reaction at the working electrode and reduction or oxidation reaction at the counter electrode, and the equilibrium potential of the electrode changes, and the change value is directly proportional to the gas concentration. It can measure SO2, NO, NO2, CO, H2S and other gases, but the sensitivity of these gas sensors is different. The order of sensitivity from high to low is H2S, NO, NO2, SO2 and CO, and the response time is usually several seconds to tens of seconds, generally less than 1 min. Their life span ranges from half a year to two or three years, while some CO sensors last for several years.
Working principle of infrared sensor: Based on the principle that different gases have special absorption characteristics for electromagnetic wave energy of infrared wavelength, the composition and content of gases are analyzed.
Infrared generally refers to electromagnetic radiation with the wavelength of 0.76 μm ~ 1000 μm, and the infrared wavelength actually used by infrared gas analyzer is about1~ 50 μ m.