Gas sensor
AssigneeCity Technology Limited
InventorsStuart Christopher Cutler, Alexander Vass
Life of this patent
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Abstract
A gas sensor comprises a cavity for containing a gas, means for generating radiation which is transmitted through the cavity and includes one or more wavelengths which is absorbed in use by a gas to be detected; and a detector for detecting radiation which has passed through the cavity. The walls of the cavity are sufficiently reflective to the radiation that the cavity is substantially uniformally illuminated with the radiation.
Claims46
A gas sensor comprising a cavity for containing a gas;
- means for generating radiation which is transmitted through the cavity and including one or more wavelengths which is absorbed in use by a gas to be detected;
- and a detector for detecting radiation which has passed through the cavity, the detector having a surface area which is visible to the interior of the cavity, wherein the radiation generating means and/or detector(s) is mounted on a printed circuit board (PCB) and is surrounded by resilient protection comprising a resilient member having one or more apertures through which the radiation means and/or respective detector(s) extend;
- and the resilient member, the PCB and the components mounted thereon are located in an electronics housing having an upper wall, the upper surface of which defines a wall of the cavity, the resilient member extending from the PCB to the lower surface of the upper wall of the electronics housing such that free volume therewithin is reduced.
A sensor according to 1, wherein the radiation generating means comprises a heating element to heat gas within the cavity so as to cause the gas to generate infra-red radiation.
A gas sensor comprising a cavity for containing a gas;
- means for generating radiation which is transmitted through the cavity and including one or more wavelengths which is absorbed in use by a gas to be detected;
- and a detector for detecting radiation which has passed through the cavity, the detector having a surface area which is visible to the interior of the cavity, the walls of the cavity being sufficiently reflective to the radiation that the cavity is substantially uniformly illuminated with the radiation, wherein the cavity is tubular, for example cylindrical, and has substantially planar end walls, adjacent to at least one of which, at least one of the means for generating radiation and the detector is positioned and wherein the ratio of the height to the width of the cavity is greater than or equal to 0.1 and less than or equal to 0.7.
A method of constructing a gas sensor, the method comprising:
- (a) inserting a tubular, optical housing, closed by a wall at one end except for at least one gas access aperture, into a tubular outer housing closed at its end adjacent the closed end of the optical housing, except for at least one gas access opening;
- (b1) fitting a resilient member over a radiation source and detector on a printed circuit board (PCB), the resilient member having one or more apertures through which the radiation means and/or respective detector(s) extend;
- (b2) inserting the so-assembled resilient member, radiation source detector and printed circuit board into a tubular electronics housing, the electronics housing having an end wall closed at one end except for one or more apertures to allow access to the source and detector, the resilient member extending from the PCB to the lower surface of the upper wall of the electronics housing such that free volume therewithin is reduced;
- (c) inserting the electronics housing into the outer housing so that it mates with the optical housing and defines therewith a substantially closed optical cavity between the end walls of the electronics and optical housings and in which a gas to be sensed is located in use, the end wall of the electronics housing forming a wall of the cavity;
- and
- (d) securing the assembled housings together.
Dependencies are inferred from the claim text.