Contamination Resistant Liquid Level Sensor Design
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Solution Overview
Problem
Existing liquid level sensors face contamination issues due to dissolved solids depositing on moving parts and electronic components, interfering with their operation, especially in appliances with automatic dispensers or reservoirs for detergents and wash aids.
Innovation Solution
A compact liquid level sensor design featuring a float supported above the liquid level with a spring for ratiometric movement, using an inductive sensor fully contained within a shielded housing to minimize contact with the liquid, and a sealed compartment with a low-profile sensor head to resist contamination and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a float moves along a guide to sense liquid height, then liquid level detection is achieved, but dissolved solids deposit on the moving float and guide, interfering with operation
Solution Approach 1:
The patent extracts the float from the liquid environment by supporting it above the liquid surface using a rod that extends through the liquid level. The float operates in a dry zone above the liquid, eliminating contact with dissolved solids while still enabling liquid level detection through the rod's position relative to the liquid surface.
Solution Approach 2:
The rod acts as an intermediary element that transmits the float's position information to the sensing mechanism. The rod extends through the liquid but the float itself remains above the liquid, using the rod as a mediator to convey level information without the float directly contacting the contaminated liquid.
2Measurement precision
If antennas are partially submerged in liquid to sense level, then liquid height sensing is achieved, but dissolved solids coat the antennas, interfering with electronic operation
Solution Approach 1:
The sensing electronics and antenna are extracted from the liquid environment and placed in a sealed housing above the liquid level. The float and rod mechanism transmits position information to the sealed housing, allowing precise measurement without the sensing components contacting the liquid.
3Ease of operation
If the float support structure is placed in the liquid to enable float movement, then float guidance is achieved, but the structure is exposed to contamination and adhesion
Solution Approach 1:
The support structure is segmented into two distinct zones: a lower portion that may contact the liquid for guidance and an upper portion that remains above the liquid level where the float operates. This segmentation allows the float to be guided while minimizing exposure of the upper support structure to contamination.
Solution Approach 2:
The float and upper support structure are extracted from the liquid environment, operating above the liquid surface. Only the lower portion of the support structure contacts the liquid, eliminating contamination from the majority of the support structure while maintaining float guidance functionality.
4Measurement precision
If the sensor head is placed close to the float for accurate sensing, then measurement precision is improved, but the sensor is more exposed to contamination
Solution Approach 1:
The sensor head is extracted from the liquid environment and placed in a sealed housing above the liquid level. The float and rod mechanism transmits position information to the sensor, enabling precise measurement without the sensor directly exposing to liquid contamination.
Solution Approach 2:
The rod and float mechanism serve as intermediaries that carry position information to the sensor head. This allows the sensor to be positioned close to the float for accurate sensing while the sealed housing protects the sensor from liquid contamination.
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 solution provides a reliable and compact liquid level sensor that effectively resists contamination, ensuring accurate liquid level detection with minimal adhesion and interference, maintaining sensor functionality even in environments with high dissolved solids content.
Implementation Method 1
a spring extending between the sensor head in the elongate float biases the elongate float downward against of buoyant forces on the elongate float
Implementation Method 2
A sensor fitting within the sealed compartment senses a height of the elongate float with respect to the sensor head
Data Source
Figure 1
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Figure 4~5
AI summary
A liquid-level sensor provides a downwardly pendent float supported above the reservoir fill height using high clearance downwardly extending fingers and a spring that resist encrustation of the float support mechanism. The spring may be a flat helix to reduce the height of the sensing mechanism when so positioned, A sensor sealed within a sensor head electrically senses the float height through a sealed compartment to be contamination resistant.