Capacitive Liquid Level Sensor Tongue Design for Condensate Management
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Solution Overview
Problem
Capacitive liquid level sensors face inaccuracies due to trapped condensate pockets caused by capillary action when installed in close proximity to mechanical parts, leading to inconsistent measurements and unnecessary pump activation or premature shutdown.
Innovation Solution
A capacitive liquid level sensor design with a tongue-shaped structure that narrows in the downward direction, allowing trapped liquid to collect in a controlled position beneath the electrodes, and a flat printed circuit board (PCB) configuration to minimize surface area and prevent interference, enabling accurate level sensing even in small spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the sensor is installed in close proximity to surrounding mechanical parts to reduce tank size, then the tank volume is reduced, but liquid pockets are trapped in gaps causing measurement inaccuracy
Solution Approach 1:
The tongue is inverted in shape, being wider at the distal end and narrower at the proximal end, which is opposite to conventional sensor designs. This inversion causes liquid to be drawn down to the narrowest part of the gap by capillary action, away from the electrode active area, preventing false readings while maintaining close proximity to surrounding parts
Solution Approach 2:
The sensor tongue has non-uniform width along its length, with different sections serving different functions: the wider distal end provides structural stability and defines the gap geometry, while the narrower proximal end allows liquid to collect away from the electrode active area, creating localized functional zones that solve the measurement accuracy problem
2Strength
If the sensor tongue is made wider to improve structural stability, then structural strength is improved, but more liquid is trapped in the gap causing greater measurement error
Solution Approach 1:
The tongue width profile is inverted compared to conventional designs: wider at the distal end for structural stability, narrower at the proximal end to guide liquid away from electrodes. This inversion simultaneously achieves both structural strength and measurement accuracy
Solution Approach 2:
The tongue exhibits asymmetric width distribution along its length, with the width varying non-uniformly to create different functional zones: the wider distal portion provides structural support while the narrower proximal portion enables liquid management, resolving the contradiction between strength and measurement precision
3Length of moving object
If the electrode active area is extended lower to detect lower liquid levels, then the detection range is extended, but trapped liquid in the gap causes false low-level readings
Solution Approach 1:
The electrode active area is deliberately terminated before the narrowest part of the gap (the extraction point), separating the measurement function from the liquid collection zone. This ensures trapped liquid is drawn away from the active area and does not interfere with readings
Solution Approach 2:
The tongue geometry is designed in advance to create a liquid collection zone below the electrode active area. This preliminary structural arrangement ensures that any liquid entering the gap is automatically directed away from the electrodes before measurement occurs, preventing false readings
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 effectively reduces inaccuracies by ensuring trapped liquid does not interfere with sensor readings, allowing for precise liquid level detection and efficient pump operation, suitable for installation within 6 mm of surrounding parts.
Implementation Method 1
capacitive liquid level sensor
Implementation Method 2
pockets of condensate tend to detach from the main body of condensate due to capillary action and are retained in gaps between the capacitive sensor and the surrounding mechanical parts
Data Source
AI summary
A capacitive liquid level sensor (1). The sensor comprises a sensor body in the form a tongue with a freely depending portion (3) extending to a distal tip (6) at its lowermost end. A set of spaced capacitive electrodes (7) extend along the tongue towards the distal tip. In use, when the distal tip (6) of the tongue is immersed in a body of liquid, the capacitance between the electrodes (7) changes depending on the depth of the body of liquid. The width of the tongue increases in the downward direction at least for part of the bottom half of the freely depending part of the tongue.