Infrared-gas measuring device i.e. infrared-gas sensor, for measuring concentration of target gas i.e. exhaust gas of vehicle, has examining circuit comparing amount of filtered infrared light with reference value

摘要

The device has a control circuit (60) with a measuring circuit that controls a wavelength-tunable filter (30) i.e. Fabry-Perot interference filter. The measuring circuit calculates the concentration of a gas based on an amount of a filtered infrared light. An examining circuit examines whether the filter operates normally, where the examining circuit compares an amount of another filtered infrared light with a reference value based on the examination result. A wavelength of the light lies within a wavelength range, where the atmospheric gas do not absorbs the light in the wavelength. An independent claim is also included for a method for measuring a gas with the aid of a wavelength-tunable filter.