Compact Gas Sensor Using Rotating Filters on Intersecting Planes
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Solution Overview
Problem
Conventional gas concentration measurement devices using the non-dispersive infrared (NDIR) absorption method are large due to the need for a rotating disc with band pass filters arranged in a circumferential direction, making them difficult to install in small spaces.
Innovation Solution
A gas concentration measurement device with a rotating member holding multiple band pass filters on intersecting planes, allowing for compact design by rotating the member around a shaft that intersects the optical axis, enabling efficient switching between filters using a stepper motor-driven rotational unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If band pass filters are arranged in the circumferential direction on a rotating disc, then multiple types of sample gas can be measured, but the device size increases and becomes difficult to install in small spaces
Solution Approach 1:
The patent transitions from a two-dimensional circumferential arrangement of filters on a disc to a three-dimensional arrangement where filters are positioned on the surface of a rotating cylinder along its longitudinal axis. This dimensional change allows multiple filters to be compactly arranged without requiring a large rotation region, thereby reducing overall device volume while maintaining multi-gas measurement capability.
Solution Approach 2:
The rotating member is designed as a cylindrical structure that can be nested within a compact housing. The filters are arranged along the longitudinal axis of the cylinder, allowing the rotation mechanism to be contained within a smaller spatial envelope compared to a disc-based system, effectively nesting the functional components within a reduced volume.
2Adaptability or versatility
If a large rotating disc is used to hold band pass filters, then filter switching is possible, but a large rotation region is required
Solution Approach 1:
The invention changes the geometry from a disc (rotating in a plane) to a cylinder (rotating around its longitudinal axis). The filters are arranged along the longitudinal axis rather than in a circumferential pattern, which dramatically reduces the required rotation region area while preserving the ability to switch between multiple filters during rotation.
3Device complexity
If the rotating shaft is arranged parallel to the infrared light direction, then filter switching is simple, but the device cannot be compacted
Solution Approach 1:
The patent employs an asymmetric arrangement where the rotating shaft is positioned perpendicular to the infrared light path rather than parallel. This asymmetric configuration, combined with the cylindrical geometry and longitudinal filter arrangement, enables compact device volume while maintaining functional effectiveness through careful optical path design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compact design reduces the device's size while maintaining sensitivity through filter switching, allowing for accurate measurement of multiple gas concentrations with reduced power consumption and increased positioning repeatability.
Implementation Method 1
n band pass filters, including a first band pass filter and a second band pass filter provided on the rotating member
Implementation Method 2
causes sample gas to absorb infrared light emitted from a light source
Implementation Method 3
A gas concentration measurement device that uses the non-dispersive infrared (NDIR) absorption method
Implementation Method 4
detects the amount of infrared light that has passed through an optical filter (band pass filter) with a detector
Data Source
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AI summary
A gas concentration measurement device (100) measures a gas concentration based on an absorbance of sample gas in a region between a light source (20) that emits infrared light and a detector (60) that detects the infrared light. The gas concentration measurement device (100) includes a rotating member that is rotatable, a first band pass filter (41) and a second band pass filter (42) provided on the rotating member, and a rotational driving unit. The first band pass filter (41) and the second band pass filter (42) are located on a pair of planes that intersect each other. The rotational driving unit rotates the rotating member around the rotating shaft to switch between a first state, in which the infrared light from the light source (20) is transmitted through the first band pass filter (41), and a second state, in which the infrared light from the light source (20) is transmitted through the second band pass filter (42).