Non-Dispersive Infrared / NDIR
The story of nondispersive IR spectroscopy (NDIR) gas analysis began back in 1943.
Today, over 100 different gases can be detected reliably from the ppm to the percent range. This method of analysis is used, in particular, in medicine to analyze respiratory gas, in the automobile industry to analyze emissions, and in chemical applications.
The gas to be analyzed is commonly channeled into a sealed room and exposed to an IR pulse source. As soon as the gas absorbs the IR radiation, the attenuation can be detected using a suitable detector. The concentration of the gas can then be determined based on the attenuation.
Gas analysis can be carried out with multispectral pyroelectric infrared detectors. These sensors combine several single-channel detectors in a single housing and are equipped with different filters. This setup allows the individual detectors to detect different gases. Currently, it is possible to carry out up to four measurements with a single detector. Multispectral pyrodetectors make it possible to design very compact gas analyzers.
NDIR is by far the most commonly used gas detection method today due to its simplicity.
Gas is passed through a measurement cell where a broadband IR source is used to emit light through the cell to a detector. The detector uses IR optical filters to filter the light into an “active channel” at the absorption wavelength of the target gas and a reference channel.
Used for CO2 detection. One of the most common gases that is detected via this method is CO2 at approx. 4.3 μm. The advantage of NDIR comes from the strength of absorption in the mid IR compared to methods in the near IR. This strong absorption allows relatively low concentrations of gas to be detected with small path lengths and inexpensive components.
Products. LASER COMPONENTS can provide detectors that have more than one channel with many filter options, one channel as a reference and the others for the gases you would like to detect. We also offer a filter that enables infrared humidity measurements in many applications.
Challenges. NDIR is also not without its challenges: selection of the correct filters to minimize crosstalk combined with the angular and temperature dependence of these filters can cause undesired results. LASER COMPONENTS has years of experience in this field, and our standard selection of filters has been carefully chosen to help you easily find the best filters for your application.
Let's get in touch!
Product Selection
Made for TLDS Equipment
