Capacitive Liquid Level Sensor with Shared Reference Electrode
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Solution Overview
Problem
Traditional liquid level sensing methods, such as pressure sensors and capacitive sensors, are expensive and suffer from low resolution and require multiple pins for capacitance value recording, making them unsuitable for many industrial and consumer applications.
Innovation Solution
A liquid level sensing system using a substrate with electrodes and sense lines, coupled with a capacitance-to-voltage converter and controller, which measures capacitance changes to detect liquid level transitions and adapt baseline values for accurate liquid level monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional pressure sensors are used for liquid level sensing, then measurement accuracy is improved, but device cost increases significantly
Solution Approach 1:
The patent replaces mechanical pressure sensors with a capacitive sensing system that uses electrical fields to detect liquid level. The sensing element measures capacitance changes between conductive electrodes as liquid level changes, eliminating the need for expensive mechanical pressure sensing components while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from pressure (in traditional sensors) to capacitance (in the new system). By measuring capacitance variations between electrodes that occur as liquid level changes, the system achieves accurate liquid level detection using low-cost capacitive measurement circuitry instead of expensive pressure sensors.
2Ease of manufacture
If traditional capacitive sensors are used for liquid level sensing, then device cost is reduced, but measurement resolution deteriorates
Solution Approach 1:
The patent divides the sensing element into multiple discrete conductive electrodes arranged vertically along the container wall. Each electrode or electrode pair corresponds to a specific liquid level range, allowing the system to detect small changes in liquid level by monitoring capacitance changes between adjacent electrodes. This segmentation provides high resolution liquid level detection while maintaining low device cost.
Solution Approach 2:
The patent replaces traditional low-resolution capacitive sensors with an improved capacitive measurement system that uses multiple electrode pairs and sophisticated capacitance-to-voltage conversion circuitry. This substitution enables high-resolution liquid level detection by precisely measuring small capacitance changes between adjacent electrodes.
3Ease of manufacture
If traditional capacitive sensors are used for liquid level sensing, then device cost is reduced, but system complexity increases due to multiple pins required for recording capacitance values
Solution Approach 1:
The patent combines multiple electrode connections into a shared reference electrode that serves as a common terminal for all capacitance measurements. The conductive substrate acts as a reference electrode that is electrically connected to all sensing electrodes, allowing capacitance measurements to be performed using minimal controller pins. This merging of multiple connections into a single reference terminal significantly reduces system complexity.
Solution Approach 2:
The conductive substrate serves multiple functions simultaneously: it acts as the structural base for mounting electrodes, provides electrical grounding, serves as a reference electrode for capacitance measurements, and enables signal routing. This multi-functionality reduces the number of separate components and controller pins needed, simplifying the overall system.
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 system provides improved resolution and cost-effectiveness by detecting liquid level changes with high accuracy, including incremental and non-incremental changes, and compensates for dielectric constant changes and measurement drift, enhancing the reliability of liquid level sensing.
Implementation Method 1
periodically measuring a capacitance of the L sets of parallel coupled conductive electrodes
Data Source
AI summary
A liquid level sensor device (10) includes a liquid level sensor element (14), a capacitance-to-voltage converter (16), and a controller (18). The liquid level sensor element (14) comprises (i) at least two sets of N conductive electrodes (22) and (ii) M sense lines (S1-S7), where M is greater than or equal to N within each set of the at least two sets of conductive electrodes. Each of the M sense lines couples to select ones of the N conductive electrodes of the at least two sets of conductive electrodes to form a number of L sets of parallel coupled conductive electrodes, where L equals M. The capacitance-to-voltage converter (16) periodically measures a capacitance of the L sets of parallel coupled conductive electrodes for each of the M sense lines. The controller (18) establishes initial measured baseline capacitance values for each of the L sets of parallel coupled conductive electrodes and an initial liquid level height value. The controller (18) also detects transitions in the measured capacitance of the L sets of parallel coupled conductive electrodes. Responsive to the detected transitions corresponding to incremental changes in measured capacitance values, the controller updates the liquid level height value.