Infrared Measurement Principle (NDIR)

A non-dispersive infrared sensor is used in gas analysis to determine the gas concentration. NDIR analysers are particularly suitable for the determination of the concentration of carbon monoxide, carbon dioxide or hydrocarbons in a gas. Components of this process are a source of infrared radiation, an irradiated tube (cuvette) with the gas to be analysed, a wavelength filter and an infrared detector. The gas which has to be analysed is pumped into the sample. To ensure the sensor does not respond to all wavelengths, an upstream filter for the respective bandpass is connected for the suitable gas. The light from the infrared source irradiates the gas in the sample chamber and the filter and then meets on the IR sensor. Ideally only the gas absorbs light of this wavelength and no other gas contained in the gas mixture. Absorption areas can also overlay and a cross-sensitivity arise. This must be either compensated, in order not to falsify the measurement results, or be avoided by a skillful selection of the frequency bands. With NDIR sensors, over 100 different gases can be detected from ppm to percentage range. In many fields of application they apply as the default method because the measurement method is non-contact and free of consumption. Measurements on NDIR principle are possible for CO, CO2, SO2, CxHy (calibrated on methane or propane) with the ecom-J2KNpro Industry and also for SO2 with the ecom-J2KNpro TECH.