Patent ID: 8471208

Claim:
A non-dispersive infrared gas sensor comprising: a substrate; an emitter disposed on the substrate and configured to provide an electromagnetic wave in response to a first control signal; a detector disposed on the substrate and configured to generate an output signal in response to a received electromagnetic wave; a light pipe having first and second openings, the first opening being disposed adjacent the emitter, the second opening being disposed adjacent the detector, the light pipe having an inner surface to reflect the electromagnetic waves so that the electromagnetic waves propagate from the first opening to the second opening; a gas flow system coupled to the light pipe to extract gas from the light pipe and to allow gas to flow into the light pipe; and a controller coupled to the emitter, the detector and the gas flow system, and configured to: control the gas flow system to extract gas from the light pipe to draw a vacuum in the light pipe in a first operational mode and to control the gas flow system to flow gas into the light pipe in a second operational mode, provide the first control signal to the emitter and to receive the output signal from the detector in the first operational mode while the vacuum is drawn in the light pipe, provide the first control signal to the emitter and to receive the output signal from the detector in the second operational mode, and calculate a ratio of the output signal from the detector in the second operational mode and the output signal from the detector in the first operational mode.