Compact Particle Sensor with Direct Photodetection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing particle counters are costly due to expensive components like pumps, sealed chambers, and precise alignment requirements, making them unaffordable for applications like indoor air quality monitoring.
Innovation Solution
A particle sensor design with a larger flow passage than the light beam, eliminating the need for expensive light collection systems and precise alignment, using a low-cost axial fan and measuring flow via pulse width, and optionally incorporating a light baffle or lens for improved resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive components like pumps, sealed chambers, and light collection systems are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent removes expensive components (pumps, sealed chambers, complex light collection systems) from the particle counter while maintaining particle detection capability. The open chamber design eliminates the need for sealed chambers and complex pumping systems, and the direct photodetector placement without complex optics reduces optical system complexity.
Solution Approach 2:
Instead of using complex light collection systems to gather scattered light, the patent inverts the approach by placing the photodetector directly in the path of scattered light without intermediate optical elements. This eliminates the need for lenses and mirrors typically required for light collection.
2Measurement precision
If precise alignment of nozzle over beam is implemented, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent removes the nozzle component entirely from the design. Instead of requiring precise alignment of a nozzle over the light beam, the open chamber design allows particles to be drawn directly into the sensing volume through simple openings, eliminating alignment requirements.
3Measurement precision
If light collection techniques with lenses and mirrors are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent removes lenses, mirrors, and other light collection components from the optical system. The photodetector is positioned to directly receive scattered light from particles in the sensing volume, eliminating the need for intermediate optical elements.
Solution Approach 2:
Instead of using complex optical systems to collect and focus scattered light, the patent places the photodetector directly in the scattered light path, inverting the traditional approach of using lenses and mirrors to gather light.
4Measurement precision
If pressure sensors and mass flow sensors are added, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent removes pressure sensors and mass flow sensors from the system. Flow rate is determined indirectly by measuring particle transit time through the light beam using the photodetector signal, eliminating the need for separate flow measurement devices.
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 design reduces costs by simplifying the sensor structure, allowing operation at low vacuum, using affordable materials, and maintaining accurate particle monitoring with improved size resolution.
Implementation Method 1
a beam of light which intersects a flow passage through the sensor
Implementation Method 2
detecting the light scattered off the particles entrained in the air flow. These particles scatter light in proportion to their size, composition, shape and other physical properties
Implementation Method 3
The photodetector converts this scattered light into an electrical signal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A compact, low cost particle sensor utilizing a photodetector (31) which directly collects light scattered by particles (33) entrained in a fluid traversing a beam of light (32). The beam of light (32) is aligned such that it is in close proximity to the photo detector (31). The beam of light (32) is typically provided by a laser and associated focusing/collimating optics. The beam of light (32) intersects a portion of the fluid flow permitting a low pressure drop system and fluid flow generated by a low cost, low pressure device such as an axial fan (50).