Liquid level detector
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Solution Overview
Problem
Existing liquid level detection systems in fluid pumping systems, particularly in air conditioning systems, face challenges with correct orientation installation and sensitivity degradation due to liquid contact, leading to potential pump failure and noise issues when pumping air.
Innovation Solution
A capacitive liquid level detector with mutually spaced capacitive sensor elements forming rings around the chamber, located outside the liquid chamber, which compares the output signals from two sensors to control the pump independently of orientation, using a thin barrier member and copper bands for enhanced sensitivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a float switch with guide rail is used for liquid level detection, then the pump can be controlled to turn on/off based on liquid level, but the device requires precise installation orientation and the float may get stuck, leading to pump failure
Solution Approach 1:
The patent replaces the mechanical float switch system with a capacitive sensing system. The capacitive sensor detects liquid level through electrical field changes rather than mechanical float movement, eliminating the guide rail and float mechanism. This allows the sensor to function reliably regardless of chamber orientation, as electrical field detection is not affected by gravity-dependent mechanical movements.
Solution Approach 2:
The patent introduces a dielectric barrier member that allows the capacitive sensor to detect liquid level while being electrically isolated from the liquid. The barrier member with conductive coating acts as an intermediary, enabling capacitive coupling between the sensor electrode and the liquid without direct contact, thus preventing corrosion while maintaining sensing functionality.
2Measurement precision
If the capacitive sensor elements are placed inside the liquid chamber, then the sensitivity to liquid level changes is maximized, but the sensor elements are exposed to liquid corrosion and sensitivity degradation
Solution Approach 1:
The patent introduces a dielectric barrier member that allows the capacitive sensor to detect liquid level while being electrically isolated from the liquid. The barrier member with conductive coating acts as an intermediary, enabling capacitive coupling between the sensor electrode and the liquid without direct contact, thus preventing corrosion while maintaining sensing functionality.
Solution Approach 2:
The patent uses a thin dielectric barrier member (film) that allows electrical field penetration for capacitive sensing while providing physical and chemical protection to the sensor elements. The thin film structure maintains electrical coupling efficiency while protecting against liquid exposure.
3Reliability
If the pump runs continuously to ensure water is pumped, then the liquid outlet is reliably cleared, but the pump may start pumping air when the reservoir is empty, causing damage and excessive noise
Solution Approach 1:
The patent implements feedback control where the capacitive sensor continuously monitors liquid level and provides real-time signals to the pump controller. The controller adjusts pump operation based on current liquid level conditions, turning the pump off when the liquid level is low to prevent air pumping, and turning it on when sufficient liquid is present, thus preventing damage while ensuring reliable liquid outlet clearing.
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
Ensures accurate liquid level detection and pump control regardless of chamber orientation, preventing pump failure and noise by maintaining sensitivity and reliability, even when the chamber is not installed correctly.
Implementation Method 1
a capacitive sensor comprising mutually spaced capacitive sensor elements forming a capacitance which is sensitive to permittivity within a region of the chamber proximate the capacitive sensor
Implementation Method 2
forming a capacitance which is sensitive to permittivity within a region of the chamber proximate the capacitive sensor
Data Source
Figure 1~2b
Figure 3
Figure 4a~4b
AI summary
A liquid level detector for use in a pump control system comprises a chamber (20) for liquid, a liquid inlet (6) to the chamber (20), a liquid outlet (7) from the chamber and connectable to a pump, and a capacitive sensor comprising mutually spaced capacitive sensor elements (21, 22; 22, 23) forming a capacitance which is sensitive to permittivity within a region of the chamber proximate the capacitive sensor. The chamber is defined at least partially by a barrier member 25 and the capacitive sensor elements are provided on the barrier member outside the chamber.