Capacitive Liquid Level Sensor for Caged Nonmetallic Containers
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Solution Overview
Problem
Existing liquid level sensors face challenges in accurately measuring liquid levels in nonmetallic bulk containers, especially when these containers are housed within outer cages, as the presence of the cage complicates the installation of capacitive sensors, which are typically used for hazardous or corrosive liquids like diesel exhaust fluid.
Innovation Solution
A capacitive liquid level sensor system with a continuous, conformable sensing element that includes a conductive strip housed within a metal channel and foam ribbon, shielded for durability and resistance to environmental factors, and a compression assembly that securely attaches the sensor to the outer cage, allowing for wireless transmission of liquid level data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor is adhered to the outer surface of the container, then liquid level detection is enabled, but installation becomes difficult when an outer cage is present
Solution Approach 1:
The patent introduces an intermediary attachment mechanism that bridges the gap between the capacitive sensor and the container surface. This intermediary structure allows the sensor to be securely mounted on the outer cage without requiring direct adhesion to the container, thus enabling liquid level detection while simplifying installation in caged configurations
Solution Approach 2:
The sensor system is divided into separate modular components: the capacitive sensing element, the attachment mechanism, and the housing. This segmentation allows each component to be optimized independently and facilitates easier installation and replacement, particularly when working within the constraints of an outer cage structure
2Measurement precision
If the sensing element is exposed to detect liquid levels, then detection capability is improved, but susceptibility to environmental influences like rain and humidity increases
Solution Approach 1:
The patent employs a flexible housing or enclosure that wraps around or covers the capacitive sensing element. This flexible shell protects the sensing element from direct exposure to environmental factors such as rain, humidity, and dust, while still allowing the electric field to penetrate through for accurate liquid level detection
Solution Approach 2:
The housing acts as an intermediary barrier between the sensing element and the external environment. It mediates the interaction by blocking harmful environmental factors while permitting the necessary electric field interaction with the liquid, thus protecting the sensor without compromising detection capability
3Reliability
If the sensor system is designed for durability with hard outer components, then resistance to environmental factors improves, but conformability to the container surface decreases
Solution Approach 1:
The patent utilizes composite material construction for the housing, combining rigid protective outer layers with flexible inner layers or mounting surfaces. This composite structure provides both the durability needed to resist environmental factors and the conformability required to adapt to the container's surface geometry
Solution Approach 2:
The housing incorporates flexible elements or thin film components that can conform to the container surface while the overall structure maintains rigid protective features. This allows the sensor system to be both durable and adaptable to different container shapes and sizes
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 provides high-resolution, reliable liquid level monitoring without direct contact, resistant to environmental influences, and can be easily installed and reused on various containers, ensuring safe and continuous measurement of hazardous liquids.
Implementation Method 1
a capacitive liquid level sensor operates by measuring a mutual capacitance between two conductors, such as between two metallic plates or electrodes. In the absence of liquid, the two conductors have an intrinsic capacitance, and the capacitance changes from the intrinsic capacitance in the presence of a liquid nearby.
Implementation Method 2
a compression assembly that securely attaches the sensor to the outer cage
Data Source
AI summary
A sensor system is described that can be attached to the outside wall of a nonmetallic container located within an outer cage, and that measures with high resolution a level of liquid inside the container using capacitance changes at the sensor system. The sensor system includes a sensing element having a metal channel that houses a foam ribbon, and a conductive strip is applied to the foam ribbon oppositely from the metal channel to form a capacitor. Sensor electronics can determine capacitance changes from which the liquid level is determined, and can transmit sensor information wirelessly to an external electronic device. The sensor system further includes a compression assembly for fixing the sensing element to the cage while maintaining the sensing element applied against an outer surface of the container in a highly conformable manner. The compression assembly includes components for attachment to the cage bars, and one or more springs bias the sensing element against the container.