Bulk Acoustic Wave Sensors for Liquid Level and Interface Detection

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Solution Overview

Problem

Existing liquid level measurement technologies face challenges in accurately detecting the level and interface between immiscible liquids, particularly when contact methods are complex and limited to binary functions, and struggle with damping issues in liquid environments.

Innovation Solution

The use of Bulk Acoustic Wave (BAW) sensors, specifically Shear Horizontal Acoustic Plate Mode (SHAPM) and Thickness Shear Mode (TSM) devices, which facilitate contact-based level monitoring, including point level, quasi-continuous level, and multiple interfaces, by utilizing shear vibrations that travel through the bulk and surface of a piezoelectric crystal substrate, reducing damping and enabling more precise measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Surface Acoustic Wave (SAW) devices are used for liquid level sensing, then the device can detect liquid presence, but the device experiences damping in liquid and is limited to binary function only

Engineering Contradiction:

Improveliquid level detection capabilityVSAvoidmeasurement function range

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces Surface Acoustic Wave (SAW) devices with Bulk Acoustic Wave (BAW) devices. BAW sensors utilize bulk acoustic waves that propagate through the entire volume of the piezoelectric substrate rather than surface waves, fundamentally changing the mechanical wave propagation mechanism. This substitution eliminates the damping limitation that constrains SAW devices to binary detection, enabling BAW sensors to provide continuous level measurement while maintaining reliable liquid presence detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Difficulty of detecting and measuring

If contact methods are used for detecting interface between two immiscible liquids, then the detection can be performed, but the hardware and software algorithms become more complex

Engineering Contradiction:

Improveinterface detection capabilityVSAvoidhardware and software complexity

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The patent utilizes the change in acoustic wave propagation parameters when transitioning between different liquid phases. By measuring changes in wave velocity, attenuation, and impedance as the acoustic wave passes through interfaces between immiscible liquids, the system can detect multiple interfaces using simplified hardware and algorithms. The parameter changes in acoustic wave characteristics provide natural discrimination between different liquid phases without requiring complex processing.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If conventional contact methods are used for liquid level measurement, then the measurement can be obtained, but the method is limited and cannot detect multiple interfaces effectively

Engineering Contradiction:

Improveliquid level measurement accuracyVSAvoidmulti-interface detection capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements a universal Bulk Acoustic Wave sensor system that can perform multiple measurement functions through a single device. The BAW sensor can detect point level, continuous level, and multiple interfaces between immiscible liquids using the same hardware platform. By analyzing different characteristics of the acoustic wave response, the system achieves multi-functionality without requiring separate sensors for each measurement type, thereby improving both precision and adaptability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

BAW sensors provide reliable and accurate detection of fluid levels and interfaces, including multiple immiscible liquids, without the need for frequency generators, offering improved complexity in sensor electronics and signal processing, and enabling discrimination between different liquid phases and gas exposure.

Implementation Method 1

shear vibrations of BAW devices are travelling both in the bulk and along the surface of the piezoelectric crystal substrate

Methodology Applied

Scientific EffectShear vibration: Vibration

Implementation Method 2

BAW device can comprise a shear horizontal acoustic plate mode (SHAPM) device or a thickness shear mode (TSM) device

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10168198B2Bulk acoustic wave (BAW) sensors for liquid level measurements

Publication Date: 2019.01.01 HONEYWELL INTERNATIONAL INC

AI summary

A method for sensing at least one level parameter of at least one liquid in a tank. At least one bulk acoustic wave (BAW) sensor is positioned inside the tank. Electrodes of the BAW sensor are at least switchably connected to a positive feedback loop across an amplifier to provide an electronic oscillator. At least one acoustic viscosity measurement is determined from an output of the electronic oscillator, wherein the output of the electronic oscillator is different when the BAW sensor contacts the liquid as compared to when the BAW sensor contacts air. The level parameter is determined from the acoustic viscosity measurement.