Patent ID: 9395246
Filing Date: 2016-07-19
CPC Classification: G01J,G01N

Claim Text:
1. A gas analyser for measuring the concentration of formaldehyde in ambient air within an enclosed environment, the gas analyser comprising a sample chamber in gaseous communication with ambient air, at least one ultraviolet light source, a detector configured to receive ultraviolet light emitted by the at least one ultraviolet light source and passed through the sample chamber, and a processor, the detector comprising at least one photosensor sensitive to ultraviolet light emitted by the at least one ultraviolet light source and operable to produce a plurality of measured ultraviolet light signals indicative of sensed ultraviolet light in each of a plurality of wavelength bands, the plurality of measured ultraviolet light signals including at least a first measured ultraviolet light signal indicative of sensed ultraviolet light in at least some of a measurement range of 337.5 nm to 346 nm or 325 nm to 332 nm, and a second said measured ultraviolet light signal indicative of sensed ultraviolet light in at least some of a reference range of 332 nm to 337 nm, 347 nm to 350 nm or 356 nm to 370 nm, wherein the processor is configured to generate a measurement output signal indicative of the concentration of formaldehyde in ambient air taking into account the first and second measured ultraviolet light signals and at least one further signal which is dependent on the concentration of nitrogen dioxide in ambient air and at least partially independent of the first and second measured ultraviolet light signals.