Turbidity Sensor Measuring Channel Geometry to Reduce Bubble Adhesion
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Solution Overview
Problem
Conventional turbidity sensors for domestic appliances face issues with bubble adhesion to the outside surface of the sensor housing, leading to inaccurate measurements due to light scattering, which is exacerbated by chemical cleaning substances and turbulent liquid movements, and surface activation methods provide only short-term solutions.
Innovation Solution
The turbidity sensor features a measuring channel with a geometric configuration that promotes flow behavior, including a constriction away from the midpoint and asymmetrical half-sections, reducing bubble adhesion by creating turbulence or laminar flow, and a smooth surface finish to minimize roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional turbidity sensors use standard sensor housing surfaces, then manufacturing is simple, but bubbles adhere to the outside surface causing measurement errors
Solution Approach 1:
The measuring channel has an asymmetric cross-sectional shape with different widths at different positions. The channel width varies along the flow direction, creating an asymmetric geometry that generates specific flow patterns (laminar or turbulent) to prevent bubble adhesion on the sensor housing surface, thereby improving measurement accuracy without complex additional components
Solution Approach 2:
The channel width parameter is changed along the flow direction, creating a varying cross-section. This parameter change modifies the flow characteristics (velocity distribution, Reynolds number) to control flow regime and prevent bubble adhesion, achieving accurate measurements through geometric parameter optimization rather than complex structural additions
2Reliability
If surface activation methods (flame, plasma, corona treatment) are used to improve hydrophilicity, then bubble adhesion is reduced short-term, but the effect declines after a while requiring renewal
Solution Approach 1:
The asymmetric channel geometry is designed from the beginning to inherently generate flow patterns that prevent bubble adhesion. This preliminary design action creates a passive, long-lasting solution that does not require subsequent surface treatment renewal, unlike temporary chemical or physical surface modifications
Solution Approach 2:
The measuring channel's asymmetric geometry enables the flow itself to serve the function of preventing bubble adhesion. The flowing liquid continuously clears bubbles from the sensor housing surface through the controlled flow patterns, making the system self-maintaining without requiring external surface treatment renewal
3Measurement precision
If the measuring path crosses the measuring channel at the midpoint, then the measurement is symmetric, but bubble adhesion occurs on the housing projections
Solution Approach 1:
The measuring channel has an asymmetric cross-sectional shape with different widths at different positions, and the measurement path is positioned asymmetrically within this channel. This asymmetric configuration creates non-uniform flow velocity distribution that prevents bubble adhesion on the housing projections while still enabling valid turbidity measurements through the liquid
Solution Approach 2:
Instead of addressing bubble adhesion only through surface properties (2D), the solution introduces a 3D geometric dimension by varying the channel cross-sectional width along the flow direction. This dimensional change creates volumetric flow patterns that actively prevent bubble adhesion throughout the measuring channel
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
This configuration effectively reduces bubble adhesion on the sensor housing projections, ensuring accurate turbidity measurements over the long term by modifying the flow pattern and surface characteristics.
Implementation Method 1
the measuring light beam is thereby attenuated to a greater or lesser extent. The degree of turbidity of the liquid can be concluded from the extent of the attenuation
Implementation Method 2
Bubbles on the outside surface of the sensor housing can interfere with the light propagation of the measuring light beam and in particular result in undesirable scattering of the measuring light beam
Implementation Method 3
The half-sections of the measuring channel that are located before and after a longitudinal midpoint of the measuring channel are configured so as to be unsymmetrical with respect to one another in terms of the channel width... creating turbulence or laminar flow
Implementation Method 4
creating turbulence or laminar flow, and a smooth surface finish to minimize roughness
Data Source
AI summary
A turbidity sensor for a water-bearing domestic appliance includes a sensor housing having a housing main part and two housing projections protruding from the housing main part side by side and at a distance from one another, where the two housing projections delimit between them a measuring channel for a liquid to be measured. One of the housing projections emits a measuring light beam along a measuring path which runs transversely through the measuring channel to the other housing projection. The measuring path crosses the measuring channel in the channel longitudinal direction remote from a point of smallest channel width of the measuring channel or the measuring channel has a constriction at a longitudinal distance from its longitudinal midpoint, at which constriction the channel width is smaller than in a region of a longitudinal midpoint.