Capacitive Level Sensor Mounting for Complex Tank Geometries
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Solution Overview
Problem
Existing capacitive level sensors face challenges in measuring liquid levels accurately in complex tank geometries, particularly when the pump module is located below the fuel level, leading to incomplete measurement ranges and potential damage from aggressive fuels, and non-moving part sensors struggle with bottom referencing.
Innovation Solution
A method for mounting a capacitive level sensor with a rigid support and foot, where the foot is fixed to the tank's bottom wall and the support is elastically attached to the top wall, allowing for precise measurement by adjusting the angle and length of the support based on tank geometry, using interdigitated electrodes and a PCB design for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rotary resistive fuel level sensor is mounted on the pump module in a wet mounting configuration, then the sensor can be installed in complex tank geometries, but the measurement range is limited and cannot reach the full fuel level
Solution Approach 1:
The patent replaces the mechanical rotary resistive sensor system with a capacitive sensing system that uses electrical fields to detect liquid level. This eliminates the need for mechanical moving parts and allows the sensor to be positioned at the bottom of the tank while still measuring the full range of liquid levels through capacitance changes caused by the dielectric properties of the liquid.
Solution Approach 2:
The patent transitions from a horizontal measurement approach (rotary sensor sweeping across the top) to a vertical measurement approach (capacitive sensor extending downward from the bottom). This dimensional change allows the sensor to measure liquid levels in complex tank geometries where the pump module is positioned below the full fuel level, enabling bottom referencing capability.
2Measurement precision
If a rotary resistive fuel level sensor is used, then level measurement is possible, but the resistive circuit card is damaged by aggressive fuels and moving parts wear or fail
Solution Approach 1:
The patent replaces the mechanical rotary sensor with a capacitive sensing system that has no moving parts. The capacitive sensor uses electrical fields to detect liquid level, eliminating mechanical wear and failure modes. The sensor elements are fixed in position and rely on changes in capacitance rather than mechanical movement, significantly improving reliability in the harsh fuel environment.
Solution Approach 2:
The patent isolates the sensitive electronic components from direct contact with aggressive fuels by using a sealed encapsulation structure. The capacitive sensing elements are protected within an inert environment that prevents fuel degradation and corrosion, while still allowing the electrical fields to penetrate and detect liquid levels accurately.
3Ease of manufacture
If non-moving part level sensors are fixed only to the top of the tank, then installation is simple, but they cannot measure to the bottom empty level of the tank
Solution Approach 1:
The patent inverts the traditional mounting approach by fixing the capacitive sensor to the bottom of the tank instead of the top. This inversion allows the sensor to extend upward into the liquid and measure levels from the bottom reference point, enabling accurate measurement of the full liquid range including the empty level. The sensor elements are positioned vertically with the longest extent reaching toward the liquid surface.
4Volume of moving object
If the pump module is located below the full fuel level in a wet mounting configuration, then space optimization is achieved, but the sensor float arm cannot reach the full stop fuel level
Solution Approach 1:
The patent replaces the mechanical float arm system with a capacitive sensing system that measures liquid level through electrical field interaction. This eliminates the need for a long float arm to reach from the pump module to the full fuel level. The capacitive sensor elements extend vertically from the bottom of the tank and detect liquid levels based on changes in capacitance as the liquid rises, achieving full measurement range without requiring the sensor to be positioned at the top.
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
This solution enables high-precision liquid level measurement in remote tank locations and those with varying heights, providing linear signals with low measurement errors (<1%) and adaptability to different tank geometries, including those with recesses, while minimizing hysteresis and dependency on fuel type.
Implementation Method 1
The capacitor used for measurement is normally present over the entire height of the tank, and its capacitance varies according to the height of liquid in the tank. The capacitor used for reference is immersed in the liquid and supplies a reference value of the dielectric constant of the liquid.
Implementation Method 2
The capacitor used for reference is immersed in the liquid and supplies a reference value of the dielectric constant of the liquid.
Implementation Method 3
They can be interdigitated (engaged comblike) electrodes which interact by interference effect; the latter are affixed to a substrate and look like printed circuits.
Data Source
Figure 1
AI summary
Method for mounting a capacitive level sensor inside a liquid tank having a bottom wall, the sensor having a foot and a measuring portion comprising at least one capacitive element supported by a rigid support extending from said foot, wherein the foot is fixedly secured to the bottom wall of the tank through a retainer, and according to which the rigid support forms an angle with the foot so that the length of the measuring portion of the sensor is higher than the height of the tank in the portion where the foot is located.