Compact Gas Sensor Using Rotating Intersecting Band Pass Filters
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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 arrangement of band pass filters, making them difficult to install in small spaces, and they face challenges in detection accuracy and sensitivity.
Innovation Solution
A compact gas concentration measurement device design featuring a rotating member with intersecting band pass filters and a waveguide member with a tapered inner surface, which reduces the size and enhances detection accuracy and sensitivity by minimizing the incident angle and energy of infrared light on the filters.
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 becomes large
Solution Approach 1:
The patent transitions from arranging filters in a single circumferential direction (2D rotation) to arranging filters on two intersecting planes (3D spatial arrangement). The rotating member includes a first plane with first band pass filters and a second plane with second band pass filters, where the two planes intersect. This dimensional change allows multiple filters to be positioned more compactly around the rotation axis, reducing the overall device volume while maintaining multi-gas measurement capability.
2Measurement precision
If the waveguide member directly guides infrared light to the detector, then the structure is simple, but detection accuracy and sensitivity are insufficient
Solution Approach 1:
The patent introduces a tapered region as an intermediary element between the waveguide member and the band pass filters. This tapered region, with its gradually changing cross-sectional area, serves as a transition zone that optimizes the optical path. It reduces the incident angle of infrared light on the filters and minimizes energy loss, thereby enhancing detection accuracy and sensitivity without significantly complicating the overall structure.
3Measurement precision
If infrared light is incident on band pass filters at a large angle, then the optical path is simple, but detection accuracy decreases
Solution Approach 1:
The patent employs a tapered region that gradually changes the cross-sectional area of the optical path. This geometric parameter change effectively reduces the incident angle of infrared light as it progresses through the tapered region toward the band pass filters. By modifying the spatial parameters of the optical path rather than changing the light source or filter properties, the system achieves improved detection accuracy while maintaining structural simplicity.
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 device achieves increased detection accuracy and sensitivity while being compact, allowing for efficient gas concentration measurement in smaller spaces.
Implementation Method 1
a waveguide member including a wave-guiding portion having a tubular inner peripheral surface
Implementation Method 2
a first band pass filter and a second band pass filter that are provided on the rotating member
Implementation Method 3
causes sample gas to absorb infrared light emitted from a light source, and then 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) includes a waveguide member (90) including an entrance portion (91) and an exit portion (92); a rotating member; a first band pass filter (41) and a second band pass filter (42) that are provided on the rotating member and located on a pair of planes that intersect each other; and a rotational driving unit. The rotating member is rotated by the rotational driving unit so that the first band pass filter (41) and the second band pass filter (42) are selectively located at a transmitting position. When a portion of the rotating member, the first band pass filter (41), or the second band pass filter (42), the portion having a maximum radius of gyration around a rotating shaft, is defined as a maximum radius portion (38), and when a rotation locus obtained by imaginarily rotating the maximum radius portion (38) around the rotating shaft in a view along the rotating shaft is defined as a reference circle (C), the exit portion (92) is located in the reference circle (C).