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Introduction to the working principle of infrared gas detector

This site2017-04-07 14:22:56

How infrared gas detectors work

The detection part of the infrared gas detector commonly used in the 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 or close the light path at the same time or alternately through a light cutting plate at a certain period.

After the measurement gas is introduced into the measurement chamber, light having a specific wavelength of the measurement gas is absorbed, thereby reducing the luminous flux that enters the infrared receiving gas chamber through the optical path of the measurement chamber. ; 而透过参比室的光通量是一定的,进入到红外线接收气室的光通量也一定。 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 measured gas concentration, the larger the difference in luminous flux transmitted through the measurement and reference chambers. This difference in luminous flux is projected to the infrared receiving air chamber with a certain period of vibration amplitude.

The receiving air chamber is divided into two halves by a few micron-thick metal thin film. The chamber is sealed with a relatively high concentration of the component gas under test. It can absorb all the incident infrared rays within the absorption wavelength range, so that the pulsating light flux becomes The periodic change in temperature can be converted into a change in pressure according to the gaseous equation, and then detected by a capacitive sensor, and the measured gas concentration is indicated after the amplification process.

In addition to capacitive sensors, quantum infrared sensors that can directly detect infrared rays can also be used. Infrared interference filters are used for wavelength selection and tunable lasers are used as light sources to form a brand-new all-solid infrared gas detector. This detector can measure the gas concentration with only one light source, one measurement room and one infrared sensor. In addition, if a plurality of filter disks with different wavelengths are used, the concentrations of various gases in the multi-component gas can be measured separately at the same time.

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