Capacitive Liquid Level Sensor for Compact Appliance Design
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Solution Overview
Problem
Existing liquid level measurement systems in home appliances, such as washing machines and water dispensers, are limited in reducing volume, making them bulky and heavy, which hinders the development of lighter and thinner designs.
Innovation Solution
A liquid level sensor with sensing electrodes and a liquid level determination circuit that scans capacitance values to determine liquid levels, using capacitance reference and threshold values set during factory calibration, allowing for accurate measurement without recalibration, thus enabling a compact and thin design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional liquid level measurement mechanisms (floating ball or glass tube with scale) are used, then liquid level can be displayed, but the volume and weight of the measurement apparatus cannot be reduced significantly
Solution Approach 1:
The patent replaces mechanical liquid level measurement mechanisms (floating ball or glass tube with scale) with a capacitive sensing system. The sensing electrodes detect liquid level through capacitance changes caused by dielectric constant differences between air and liquid, eliminating the need for bulky mechanical components while maintaining measurement functionality.
Solution Approach 2:
The patent utilizes changes in capacitance parameters to detect liquid level. By monitoring capacitance variations of sensing electrodes as liquid level changes, the system translates physical liquid level into electrical parameter changes, enabling compact sensor design with high measurement precision.
2Weight of moving object
If conventional liquid level measurement mechanisms are used, then liquid level can be displayed, but the overall weight cannot be reduced
Solution Approach 1:
The patent replaces heavy mechanical components (floating ball, glass tube) with lightweight sensing electrodes and electronic circuitry. The capacitive sensing mechanism uses electrical fields rather than mechanical buoyancy or visual scales, dramatically reducing sensor weight while maintaining reliable liquid level detection through capacitance measurements.
Solution Approach 2:
The patent creates an electrical copy of the liquid level information through capacitance measurements. Instead of using physical mechanical indicators, the system captures liquid level data through electrical parameter changes, producing a lightweight electronic representation of liquid level status that maintains measurement reliability.
3Volume of moving object
If capacitance sensing is used for liquid level detection, then volume can be reduced, but measurement accuracy may be affected by environmental factors
Solution Approach 1:
The patent performs factory calibration before deployment to establish baseline capacitance reference values for each sensing electrode. During calibration, the system stores reference capacitance values in non-volatile memory, enabling the sensor to compensate for environmental variations and maintain measurement accuracy without requiring recalibration in the field.
Solution Approach 2:
The patent implements a feedback mechanism where the liquid level determination circuit continuously compares current capacitance values against stored reference values. The system calculates capacitance variation values and uses threshold comparisons to determine liquid level, providing automatic compensation for environmental factors and maintaining measurement precision in compact sensor design.
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 liquid level detection in a small form factor, preventing issues associated with conventional capacitance sensing methods and allowing for integration into smaller appliances.
Implementation Method 1
scans capacitance values of the sensing electrodes to determine a liquid level of a liquid in the liquid storage container based on current capacitance values of the sensing electrodes
Data Source
AI summary
A liquid level sensor and a method for sensing a liquid level adapted to a liquid storage container are provided. The liquid level sensor includes a plurality of sensing electrodes and a liquid level determination circuit. The sensing electrodes are disposed on a side wall of the liquid storage container and correspond to different liquid levels. The liquid level determination circuit is coupled to the sensing electrodes and stores a plurality of capacitance reference values and a plurality of capacitance threshold values in response to a tuning command received from a host during factory calibration. The capacitance reference values are locked after the factory calibration. After the factory calibration, the liquid level determination circuit scans capacitance values of the sensing electrodes to determine a liquid level of a liquid in the liquid storage container based on current capacitance values of the sensing electrodes.