Dual-Path Extinction Sensor for Separating Absorption and Scattering
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Solution Overview
Problem
Existing methods for determining concentration based on extinction measurements cannot separate absorption and scattering, requiring a separate model for each medium and location, making it difficult to adapt to changing conditions and compositions.
Innovation Solution
A method using two different optical path lengths to measure extinction, allowing for the determination of a measured quantity independent of location and environmental conditions, with a universal model that separates absorption and scattering, enabling determination of concentration, absorption, scattering, or turbidity independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single optical path length is used for extinction measurement, then the measurement is simple and quick, but the measured quantity cannot be determined accurately when medium composition changes
Solution Approach 1:
The measurement system is segmented into multiple optical path lengths (first path length and second path length) to measure extinction at different depths. This segmentation allows the system to distinguish between absorption and scattering effects by comparing measurements at different path lengths, thereby improving measurement precision without requiring complex additional hardware beyond what is already present in the sensor arrangement.
2Adaptability or versatility
If separate models are used for each medium and location, then measurement accuracy can be maintained, but the system cannot adapt to changing conditions and requires frequent model adjustments
Solution Approach 1:
The measurement system achieves universality by using multiple optical path lengths to create a universal model that can handle different media and conditions. The system measures extinction at both the first path length and second path length, then uses these combined measurements in a universal model that automatically adapts to different medium compositions, eliminating the need for separate models for each medium and location while maintaining operational efficiency.
3Measurement precision
If absorption and scattering are not separated, then the measurement system remains simple, but accurate determination of concentration and other measured quantities is not possible for unknown media
Solution Approach 1:
The measurement approach segments the extinction measurement into two distinct components by measuring at different optical path lengths. The first path length measurement captures one component of extinction while the second path length measurement captures another component, allowing the system to separate absorption and scattering effects through mathematical processing of the two measurements, thereby enabling accurate concentration determination for unknown media.
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
Enables accurate determination of concentration and other measured quantities regardless of medium composition or environmental changes, using a single sensor arrangement with multiple path lengths and LEDs, allowing for continuous operation without model adjustments.
Implementation Method 1
radiation of light into the medium and measurement of the extinction after a first path length; radiation of light into the medium and measurement of the extinction after a second path length
Implementation Method 2
The measurement principle for determining concentration is based upon the Lambert-Beer law. A linear dependency between the extinction of light and the concentration of a substance to be measured exists for low and medium concentrations
Implementation Method 3
The light is thereby converted by a photodiode into photoelectric current. The final conversion of the determined extinction into the concentration takes place by means of a mathematical model
Implementation Method 4
The extinction has several different causes. On the one hand, there is the scattering at particles located in the medium, and, on the other hand, there is the absorption of the radiation in the medium and at the particles
Data Source
AI summary
A method is disclosed for determining a measured quantity, correlated with an extinction, in a medium, including the steps: radiation of light into the medium and measurement of the extinction after a first path length; radiation of light into the medium and measurement of the extinction after a second path length, wherein the first path length differs from the second path length; and determination of the measured quantity correlated with the extinction using the extinction after first path length and extinction after second path length. Additionally disclosed is a sensor arrangement for execution of the method.