Common principles of infrared gas detection:
Measuring this absorption spectrum can identify the type of gas; measuring the absorption intensity can determine the concentration of the measured gas. Infrared detectors have a wide range of use. They can not only analyze gas components, but also solution components. They have high sensitivity, rapid response, can provide online continuous indication, and can also form a regulating 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 measurement chamber and the other is the reference chamber. The two chambers open and close the light path simultaneously or alternately in a certain period through the light-cutting plate. After the gas to be measured is introduced into the measurement chamber, the light with the specific wavelength of the gas to be measured is absorbed, thereby reducing the light flux that passes through the optical path of the measurement chamber and enters the infrared receiving gas chamber. The higher the gas concentration, the less the luminous flux entering the infrared receiving gas chamber; while the luminous flux passing through the reference chamber is constant, the luminous flux entering the infrared receiving gas chamber is also constant. Therefore, the higher the concentration of the measured gas, the greater the difference in luminous flux passing through the measurement chamber and the reference chamber. This luminous flux difference is projected to the infrared receiving air chamber with a certain periodic vibration amplitude. The receiving gas chamber is divided into two halves with a metal film a few microns thick. The chamber is sealed with a relatively high concentration of the measured component gas. It can absorb all the incoming infrared rays within the absorption wavelength range, so that the pulsating light flux becomes The periodic changes in temperature can be converted into changes in pressure according to the gas equation, and then detected by a capacitive sensor. After amplification, the measured gas concentration is indicated. In addition to capacitive sensors, quantum infrared sensors that directly detect infrared rays can also be used, using infrared interference filters for wavelength selection and tunable lasers as light sources, forming a new all-solid-state infrared gas detector. This kind of detector can complete the measurement of gas concentration using only one light source, one measurement chamber and one infrared sensor. In addition, if filter disks equipped with multiple different wavelengths are used, the concentrations of various gases in multi-component gases can be measured simultaneously.
