Dielectric-Insensitive Fluid Level Sensor Using Series Capacitor Stacks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing capacitive fluid level sensors are sensitive to variations in dielectric constants, leading to erroneous readings for fluids with unknown dielectric properties, especially when non-homogeneous mixtures are present, and require a reference capacitor that must be fully submerged, causing inaccuracies in measuring fluid levels below the reference height.
Innovation Solution
A dielectric-constant-insensitive fluid level sensor design that uses a series capacitor arrangement, where the impact of dielectric constant variations is minimized by grouping capacitors into stacks, allowing accurate measurement without prior knowledge of the fluid's dielectric constant, and eliminating the need for a reference capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference capacitor is used to compensate for dielectric constant variations, then measurement accuracy for different fluid mixtures is improved, but the reference capacitor must be fully submerged which causes erroneous output for fluid levels below reference height and makes it sensitive to non-homogeneous fluid mixtures at the bottom
Solution Approach 1:
The sensor is divided into multiple capacitive elements arranged in a stack, where each element contributes to the total capacitance. This segmentation allows the measurement to be distributed across multiple points rather than relying on a single reference capacitor at the bottom, thereby avoiding sensitivity to non-homogeneous mixtures and enabling accurate low-level measurements.
Solution Approach 2:
The invention extracts and eliminates the reference capacitor component from the sensor design. By removing this problematic element that caused erroneous outputs for low fluid levels and sensitivity to bottom-layer non-homogeneous mixtures, the patent achieves more reliable measurements across all fluid levels without requiring the reference capacitor to be submerged.
2Measurement precision
If capacitive plates are used to measure fluid level, then the sensor can detect fluid level variations, but the measurement is sensitive to dielectric constant variations of the fluid
Solution Approach 1:
Each capacitive element in the stack has locally optimized properties, and their combined effect creates a measurement system whose overall sensitivity to dielectric constant variations is reduced. The distributed arrangement means that local variations in dielectric constant affect only individual elements minimally, and the total capacitance integrates these effects in a way that maintains measurement precision while reducing harmful sensitivity.
Solution Approach 2:
The sensor uses a composite structure of multiple capacitive elements with different characteristics arranged in a stack. This composite approach creates a measurement system that leverages the combined properties of all elements, resulting in a total capacitance that is less sensitive to dielectric constant variations of the fluid while maintaining accurate fluid level detection.
3Measurement precision
If a reference capacitor is required at the bottom of the fluid container, then dielectric constant compensation is achieved, but the device complexity increases and prior knowledge of fluid properties is required
Solution Approach 1:
The reference capacitor is extracted and removed from the sensor design. This elimination simplifies the device structure by removing the requirement for a separate reference capacitor component and its associated mounting and wiring complexity, while the stacked capacitive elements provide the necessary measurement functionality without requiring prior knowledge of fluid dielectric properties.
Solution Approach 2:
The stacked capacitive elements serve multiple functions simultaneously: they provide the primary measurement capability for fluid level detection and inherently provide dielectric constant compensation through their collective response. This multi-functionality eliminates the need for a separate reference capacitor and reduces device complexity while maintaining measurement precision across different fluid types.
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 sensor provides accurate fluid level measurements with minimal error due to dielectric constant variations, maintaining a stable total capacitance across different fluid levels and blends, ensuring reliable readings even in unknown fluid mixtures.
Implementation Method 1
a sensor utilizes capacitive plates, which interacting with the fluid, are excited with an alternating voltage to generate a signal current that varies based on the fluid level
Implementation Method 2
variations in the dielectric constant of the fluid has a minor impact on the total capacitance of the capacitor stack
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A dielectric-constant-insensitive fluid level sensor for directly inserting into a high dielectric constant fluid is disclosed. According to one embodiment, the fluid level sensor includes a first set of stacked series capacitors where each capacitor in the first set is formed by two coplanar electrodes and a dielectric space between the electrodes. Each stack of series capacitors in the first set includes at least one capacitor having a first molded carrier as the dielectric space in series with another capacitor having a first fluid cavity as the dielectric space. In this embodiment, the total capacitance of the first set of stacked series capacitors varies as a function of the level of the fluid within the first fluid cavity.