SAW Sensor Frequency Shifts for Humidity and Temperature

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Solution Overview

Problem

Sensing devices using interdigitated transducers (IDTs) face limitations in measuring phenomena with sufficient resolution and transmitting measurements in certain environments, and are costly and difficult to manufacture, making them unsuitable for some applications.

Innovation Solution

A humidity and temperature sensing device incorporating surface acoustic wave (SAW) components, including a temperature SAW component, a humidity SAW component, and a reference SAW component on a piezoelectric layer, which convert electrical energy to mechanical energy and back, allowing for measurement of environmental conditions by analyzing frequency variations of surface waves.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If interdigitated transducers (IDTs) are used to sense phenomena, then measurement capability is provided, but manufacturing cost and difficulty increase

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidmanufacturing cost and difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive, difficult-to-manufacture IDT-based sensing devices with a simpler, cheaper sensing device that uses a piezoelectric layer with SAW components. The invention deliberately chooses a less complex alternative that achieves sufficient measurement capability at lower manufacturing cost, aligning with the principle of using simpler, more economical solutions when they meet the required performance level.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Measurement precision

If IDT-based sensing devices are used, then sensing function is achieved, but device complexity increases

Engineering Contradiction:

Improvesensing functionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes the complex IDT components from the sensing device, replacing them with a simpler piezoelectric layer structure with SAW components. This extraction of the problematic IDT element eliminates the associated complexity while preserving the essential sensing function through the piezoelectric material's inherent properties.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent substitutes the mechanical/electrical IDT transducer system with a piezoelectric field-based system. Instead of using interdigitated electrodes to generate and detect mechanical waves, the invention uses the piezoelectric effect to directly convert electrical signals to mechanical surface waves and back, simplifying the device architecture.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If IDT-based sensing devices are used, then measurement capability is provided, but resolution and environmental transmission capability are limited

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidresolution and environmental transmission capability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the fundamental operating parameters of the sensing device by transitioning from IDT-based electrical-mechanical transduction to piezoelectric-based surface acoustic wave sensing. This parameter change enables better resolution and environmental transmission capability through the use of surface waves that are less susceptible to environmental interference and provide higher measurement precision.

Inventive Principle:

Principle #35Parameter changes

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 device effectively measures temperature and humidity by differentiating frequency shifts caused by environmental factors, reducing manufacturing costs and improving resolution, enabling accurate and efficient sensing without the need for a power supply.

Implementation Method 1

a piezoelectric layer, wherein the first SAW component, the second SAW component, and the third SAW component are on a surface of the piezoelectric layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

Methodology Applied

Scientific EffectSurface acoustic wave: Surface Acoustic Wave

Data Source

PatentUS9097638B2Sensing devices and methods

Publication Date: 2015.08.04 HONEYWELL INTERNATIONAL INC

AI summary

Embodiments of the present disclosure include devices and methods for humidity and temperature sensing. For example, in one embodiment, a sensing device can include a first surface acoustic wave (SAW) component, wherein the first SAW component is a temperature component, a second SAW component, wherein the second SAW component is a humidity component, a third SAW component, wherein the third SAW component is a reference component, and a piezoelectric layer, wherein the first SAW component, the second SAW component, and the third SAW component are on a surface of the piezoelectric layer.