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The infrared light is emitted and passes through the sample gas, a reference gas with a known mixture of the gases in question and then through the "detector" chambers containing the pure forms of the gases in question. When a "detector" chamber absorbs some of the infrared radiation, it heats up and expands.
A nondispersive infrared sensor (or NDIR sensor) is a simple spectroscopic sensor often used as a gas detector.It is non-dispersive in the fact that no dispersive element (e.g a prism or diffraction grating as is often present in other spectrometers) is used to separate out (like a monochromator) the broadband light into a narrow spectrum suitable for gas sensing.
The choice of infrared wavelengths used for the measurement largely defines the detector's suitability for a particular applications. Not only must the target gas (or gases) have a suitable absorption spectrum, the wavelengths must lie within a spectral window so the air in the beam path is itself transparent. These wavelength regions have been ...
Infrared (IR) point sensors use radiation passing through a known volume of gas; energy from the sensor beam is absorbed at certain wavelengths, depending on the properties of the specific gas. For example, carbon monoxide absorbs wavelengths of about 4.2-4.5 μm. [ 6 ]
The key components are an infrared source, a light tube, an interference (wavelength) filter, and an infrared detector. The gas is pumped or diffuses into the light tube, and the electronics measure the absorption of the characteristic wavelength of light. NDIR sensors are most often used for measuring carbon dioxide. [2]
The transmitted beams from two infrared sources are superimposed onto an internal beam splitter. 50% of the overlapping sample and reference signal is passed through the gas measuring path and reflected back onto the measuring detector. The presence of combustible gas will reduce the intensity of the sample beam and not the reference beam, with ...
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