Capacitive Liquid Level Sensor with Multi-Sensor Failure Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional liquid level control systems for pumps in sump and water tanks are prone to errors due to mechanical wear, humidity sensitivity, and contamination issues, leading to inefficient operation and potential flooding or under-pumping, especially with capacitive sensors that can be affected by dielectric material buildup.
Innovation Solution
A method and apparatus using multiple capacitive sensors positioned at varying heights to detect liquid levels and a control circuit that adjusts pump operation based on sensor failures, compensating for fouled sensors by altering the pump's switching behavior to maintain accurate liquid level control, including detection of false positives and alarm activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive sensors are used for liquid level control, then transient water imbalances can be prevented, but false positive detection occurs due to dielectric material buildup
Solution Approach 1:
The system divides the sensing function into multiple capacitive sensors positioned at different heights (first, second, and third sensors). This segmentation allows the system to detect liquid levels at multiple thresholds and identify false positives by comparing readings across sensors, thereby maintaining measurement accuracy despite dielectric buildup on individual sensors.
Solution Approach 2:
The control circuit continuously monitors sensor outputs and uses feedback logic to detect when a sensor provides false positive readings. When a false positive is detected (e.g., a sensor indicates liquid presence when no liquid is actually present at that level), the system adjusts pump operation accordingly, preventing incorrect pump activation while maintaining reliable liquid level control.
2Ease of operation
If mechanical switches with moving parts are used, then liquid level control can be achieved, but wear and malfunction occur over time
Solution Approach 1:
The patent replaces mechanical switches with moving parts (diaphragms, springs, rods, floats, balls) with capacitive sensors that have no moving parts. The capacitive sensors detect liquid levels through electrical field changes, eliminating mechanical wear and improving reliability while maintaining ease of operation for automatic liquid level control.
3Measurement precision
If electrical or optical probes are used, then liquid level detection can be performed, but sensitivity to humidity, moisture, temperature, and voltage variations causes erroneous results
Solution Approach 1:
By using multiple capacitive sensors at different heights rather than a single probe, the system can compare readings and identify environmental interference. The segmented approach allows the control circuit to distinguish between actual liquid level changes and false signals caused by humidity, moisture, temperature, or voltage variations.
Solution Approach 2:
The capacitive sensors are designed to detect specific capacitance changes corresponding to liquid presence while being less sensitive to environmental parameter variations. The control circuit monitors capacitance values and uses threshold-based detection to filter out erroneous signals caused by changes in humidity, moisture, temperature, or voltage, maintaining accurate liquid level detection.
4Measurement precision
If probes are used for liquid level sensing, then liquid level can be detected, but contamination of probes adversely affects performance
Solution Approach 1:
The patent replaces physical probes that are susceptible to contamination with capacitive sensors that detect liquid levels through electrical field changes. Since capacitive sensors do not require physical contact with the liquid, they are not affected by contamination, maintaining accurate liquid level sensing even in dirty or contaminated environments.
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 effectively prevents flooding and under-pumping by accurately detecting sensor failures and adjusting pump operation, ensuring reliable liquid level management and reducing the risk of pump motor burn-out through intelligent control.
Implementation Method 1
a first capacitive sensor and a second capacitive sensor disposed above the first capacitive sensor
Data Source
AI summary
Described herein is technology for, among other things, controlling a pump submersed in a liquid, where the pump includes a plurality of capacitive sensors. The capacitive sensors include a first capacitive sensor and a second capacitive sensor disposed above the first capacitive sensor. The technology involves sensing liquid levels with the capacitive sensors, activating the pump after the second capacitive sensor detects the liquid in a normal mode of operation, deactivating the pump after the first capacitive sensor no longer detects the liquid in the normal mode of operation, detecting a failure of one or more capacitive sensors, and adjusting the operation of the pump to compensate for the failure of the one or more capacitive sensors.