The Detection Principle of Gas Test Gauge

  • Gas test gauge is an instrumentation tool for gas leakage concentration detection, including portable gas detectors, hand-held gas detectors, fixed gas detectors, online gas detectors, etc. The gas sensor is mainly used to detect the types of gases present in the environment. The gas sensor is a sensor used to detect the composition and content of the gas.

    It is generally believed that the definition of a gas sensor is based on the detection target, that is to say, any sensor used to detect gas composition and concentration is called a gas sensor, regardless of whether it uses a physical method or a chemical method. For example, sensors that detect gas flow are not considered gas sensors, but thermal conductivity gas analyzers are important gas sensors, although they sometimes use generally the same detection principles.

    Take the common infrared gas detector as an example to illustrate the principle of the gas detector:

    Measuring this absorption spectrum can identify the type of gas; measuring the absorption intensity can determine the concentration of the gas being measured. The infrared detector has a wide range of use, which can not only analyze the gas composition, but also the solution composition, and has high sensitivity, rapid response, and continuous online instructions, and it can also form an adjustment system. The detection part of the infrared gas detector commonly used in industry is composed of two parallel optical systems with the same structure.

    One is the measurement room and the other is the reference room. The two chambers open and close the light path at the same time or alternately at a certain cycle through the light cutting board. After the gas to be measured is introduced into the measurement chamber, the light with the unique wavelength of the gas to be measured is absorbed, so that the luminous flux entering the infrared receiving gas chamber through the optical path of the measurement chamber is reduced. The higher the gas concentration, the less the luminous flux entering the infrared receiving gas chamber; and the luminous flux passing through the reference chamber is constant, and the luminous flux entering the infrared receiving gas chamber is also constant. Therefore, the higher the concentration of the gas to be measured, the greater the difference in luminous flux passing through the measurement chamber and the reference chamber. This difference in luminous flux is projected to the infrared receiving air chamber with the amplitude of a certain period of vibration. The receiving gas chamber is divided into two halves with a few micrometers thick metal film. The chamber is sealed with a large concentration of the measured component gas, which can absorb all the incoming infrared light within the absorption wavelength range so that the pulsating light flux becomes The periodic change of temperature can be converted into a pressure change according to the gas equation and then detected by a capacitive sensor. After amplifying, the concentration of the gas to be measured can be indicated. In addition to capacitive sensors, quantum infrared sensors that directly detect infrared can also be used, and infrared interference filters are used for wavelength selection and tunable lasers are used as light sources to form a new all-solid-state infrared gas detector. This kind of detector only uses a light source, a measuring chamber, and an infrared sensor to complete the gas concentration measurement. In addition, if filter discs equipped with multiple different wavelengths are used, the concentrations of various gases in multi-component gases can be measured separately at the same time.

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