Capacitive Fluid Level Sensing Using Tank Wall and Vane Electrodes

Solution Overview

Problem

Existing methods for determining the amount of fluid in a satellite's fuel tank are inaccurate, leading to premature retirement and wastefulness, and require additional hardware that increases weight and complexity.

Innovation Solution

A capacitance sensing system using a vane with electrically conductive material within the tank, coupled to the tank wall, measures capacitance changes to determine fluid levels without adding new hardware, leveraging capillary action and insulating layers for accurate fluid extraction and measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional fluid level estimation methods are used, then the satellite can operate with existing hardware, but the measurement precision is insufficient leading to premature retirement

Engineering Contradiction:

Improvefluid level measurement accuracyVSAvoidsatellite operational life

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces traditional mechanical or book-keeping estimation methods with a capacitive sensing system that uses electrical field interactions between the tank wall, vane, and fluid to directly measure fluid level with high precision, eliminating the need for complex mechanical sensors or manual tracking

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an electrically insulating layer as an intermediary between the conductive tank wall and conductive vane, creating a capacitive structure where the fluid acts as a dielectric medium that modulates capacitance based on its level, enabling indirect but precise measurement

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If additional hardware is added to the tank for fluid level sensing, then measurement precision improves, but the device complexity and weight increase

Engineering Contradiction:

Improvefluid level measurement accuracyVSAvoidtank hardware complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the tank wall and vane serve dual functions: the tank wall contains the fluid while also acting as one electrode of the capacitive sensor, and the vane facilitates fluid extraction while also serving as the other electrode, eliminating the need for separate sensing hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent enables the tank structure itself to provide the sensing function by utilizing its existing conductive components (tank wall and vane) as the capacitive elements, allowing the system to sense fluid level without requiring external or additional sensing devices

Inventive Principle:

Principle #25Self-service

3Measurement precision

If additional hardware is added to the tank for fluid level sensing, then measurement precision improves, but the weight of the satellite increases

Engineering Contradiction:

Improvefluid level measurement accuracyVSAvoidsatellite weight

Core Design Contradiction:

Measurement precisionVSWeight of moving object

Solution Approach 1:

The patent makes the tank wall and vane serve dual functions: the tank wall contains the fluid while also acting as one electrode of the capacitive sensor, and the vane facilitates fluid extraction while also serving as the other electrode, eliminating the need for separate sensing hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent enables the tank structure itself to provide the sensing function by utilizing its existing conductive components (tank wall and vane) as the capacitive elements, allowing the system to sense fluid level without requiring external or additional sensing devices

Inventive Principle:

Principle #25Self-service

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 method provides accurate fluid level sensing without additional hardware, reducing satellite weight and complexity, allowing for more efficient fuel usage and extended satellite life by accurately determining remaining fuel, thus preventing premature retirement.

Implementation Method 1

the capacitance sensing device can measure a capacitance between the at least one portion of the vane and the at least one portion of the tank wall

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

an electrically insulating layer may be provided on a surface of a hardware component inside the tank to prevent electrical shorting between the vane and the tank wall

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Implementation Method 3

A capillary channel between the vane and the inner surface of the wall may facilitate extraction of liquid from the tank

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS8620603B1Fluid level sensing

Publication Date: 2013.12.31 THE BOEING CO

AI summary

A tank to contain a fluid includes a tank wall having an inner surface. A vane is disposed within the tank. The vane is configured to facilitate extraction of fluid from the tank. The vane may include an electrically conductive material. The tank also includes a first connector to electrically couple at least one portion of the tank wall to a capacitance sensing device and a second connector to electrically couple at least one portion of the vane to the capacitance sensing device.