Patent ID: 7679047
Filing Date: 2010-03-16
Classification: G01N

Abstract:
1. A gas sensing apparatus for sensing gas that absorbs infrared light at a first wavelength, the gas sensing apparatus comprising: an infrared source that emits the infrared light; a wavelength tunable filter that selectively allows passage of the infrared light at a specific wavelength; a control circuit that includes a measurement circuit and a check circuit, the measurement circuit controlling the wavelength tunable filter, so that the wavelength tunable filter allows passage of the infrared light at the first wavelength and outputs a first filtered infrared light, the check circuit controlling the wavelength tunable filter, so that the wavelength tunable filter allows passage of the infrared light at a second wavelength and outputs a second filtered infrared light; an infrared detector that detects a first amount of the first filtered infrared light and a second amount of the second filtered light; and a housing for accommodating the infrared light source, the wavelength tunable filter, and the infrared detector, the housing having an inlet for introducing the gas therein, wherein the measurement circuit calculates concentration of the gas based on the first amount of the first filtered infrared light, the check circuit checks whether the wavelength tunable filter operates normally by comparing the second amount of the second filtered infrared light with a reference value, the second wavelength is within a wavelength range where atmospheric gases do not absorb the infrared light, the check circuit controls the wavelength tunable filter, so that the wavelength tunable filter allows passage of the infrared light at a third wavelength and outputs a third filtered infrared light, the third wavelength being within the wavelength range, the infrared detector detects a third amount of the third filtered infrared light as the reference value, and, the check circuit calculates a ratio between the second amount and the third amount and checks whether the wavelength tunable filter operates normally based on a deviation of the ratio from one.