Gas-Tight Tube Liquid Level Sensor Isolates MEMS from Corrosion

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Solution Overview

Problem

Existing liquid pressure sensors are costly and require frequent calibrations due to their complex construction and susceptibility to corrosion and debris accumulation, making them unsuitable for long-term use in harsh environments.

Innovation Solution

A sensor system that uses a gas-tight tube with a gas pressure sensing device to measure liquid levels without direct contact, employing MEMS pressure sensing devices and a sealed pouch with inert liquid to protect the electronics and prevent corrosion, allowing for accurate and durable liquid level measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If strain gauge transducers are used to sense liquid pressure directly, then measurement capability is achieved, but the sensor becomes susceptible to corrosion and debris accumulation, requiring frequent calibration

Engineering Contradiction:

Improvesensor durabilityVSAvoidcalibration frequency

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces a gas-tight tube as an intermediary barrier between the liquid environment and the pressure sensing device. The tube allows pressure transmission from the liquid to the gas column inside, which then transmits pressure to the sensing device, preventing direct contact with corrosive liquids and debris while maintaining measurement capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical contact between the strain gauge transducer and liquid with an indirect pressure transmission system using a gas column. The gas column acts as a pressure transfer medium, substituting the need for direct mechanical interaction and eliminating corrosion issues

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If corrosion resistant stainless-steel components are used, then sensor durability is improved, but manufacturing cost increases

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The gas-tight tube serves as a protective intermediary that shields the pressure sensing device from direct exposure to corrosive environments. This allows the use of less expensive materials for the sensing device itself, as the tube provides the corrosion barrier rather than requiring the entire sensor assembly to be made from expensive stainless steel

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The gas-tight tube acts as a sacrificial protective element that can be easily replaced if needed, allowing the use of more cost-effective materials for the permanent sensing components. The tube absorbs the environmental harshness, protecting the valuable sensing device

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If the pressure sensing device is isolated from liquid contact, then corrosion is minimized, but direct pressure measurement capability is lost

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidpressure measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent uses a column of gas (pneumatic principle) inside the tube to transmit pressure from the liquid interface to the sensing device. The gas column transmits the pressure signal accurately while maintaining physical isolation, leveraging fluid pressure transmission properties to solve both isolation and measurement requirements

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 provides cost-effective, high-accuracy liquid level measurements with reduced maintenance needs, as the gas pressure sensing device remains isolated from the liquid, minimizing the impact of corrosion and debris, and maintaining accuracy across various pressures and temperatures.

Implementation Method 1

a gas pressure sensing device adapted to sense a pressure of a gas within the tube

Methodology Applied

Scientific EffectGas pressure sensing:

Implementation Method 2

a sealed pouch containing a pressure sensing device adapted to sense a pressure of a liquid in which the pouch is submerged

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentUS11519772B2Liquid pressure and level sensor systems and sensors, methods, and applications therefor

Publication Date: 2022.12.06 EVIGIA SYSTEMS INC

AI summary

Pressure sensor systems for measuring a liquid pressure and deriving a liquid level from the measured pressure using gas pressure sensing devices. In one embodiment, liquid pressure results in compression or decompression of a trapped gas (as an example, air), wherein the gas pressure is detected by a gas pressure sensing device directly or a gas pressure sensing device that is protected inside a flexible pouch filled with a liquid. In another embodiment, a gas pressure sensing device is packaged in a flexible pouch filled with an inert liquid to protect the sensing device and circuit thereof from external contaminants while accurately transferring pressure from the liquid through a protective barrier. Application of such sensors in a wireless flood or a wireless liquid level measurement system is described as well.