Introduction to the Principle of Analytical Gas Detector

　　Measuring this absorption spectrum can identify the type of gas; measuring the absorption intensity can determine the concentration of the measured gas. The infrared detector has a wide range of uses. It can not only analyze gas components, but also analyze solution components. It has high sensitivity, rapid response, can indicate continuously online, and can also form an adjustment system. The detection part of the infrared gas detector commonly used in industry consists of two parallel optical systems with the same structure.

　　One is the measuring chamber, and the other is the reference chamber. The two chambers open and close the optical path simultaneously or alternately at a certain period through the light-cutting plate. After the measured gas is introduced into the measuring chamber, the light with the wavelength unique to the measured gas is absorbed, thereby reducing the light flux that passes through the optical path of the measuring chamber and enters the infrared receiving chamber. The higher the gas concentration, the less light flux enters the infrared receiving chamber; while the light flux passing through the reference chamber is constant, and the light flux entering the infrared receiving chamber is also constant. Therefore, the higher the concentration of the measured gas, the greater the difference in light flux passing through the measuring chamber and the reference chamber. This light flux difference is projected onto the infrared receiving chamber with an amplitude of a certain period of vibration. The receiving chamber is divided into two halves by a metal film several microns thick. The chamber is sealed with a high concentration of the measured component gas, which can absorb all the incident infrared rays within the absorption wavelength range, thereby converting the pulsating light flux into a periodic change in temperature. The temperature change can then be converted into a pressure change according to the gas state equation, and then detected by a capacitive sensor, and the concentration of the measured gas is indicated after amplification. In addition to capacitive sensors, quantum infrared sensors that directly detect infrared rays can also be used, and infrared interference filters are used for wavelength selection and equipped with adjustable lasers as light sources to form a new all-solid infrared gas detector. This detector can measure gas concentrations with only one light source, one measuring chamber, and one infrared sensor. In addition, if a filter disc equipped with multiple different wavelengths is used, the concentrations of various gases in multi-component gases can be measured simultaneously.