Hermetic Accelerometer Silver Oxygen Window
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Solution Overview
Problem
Piezoelectric sensors face degradation due to Oxygen depletion at high temperatures, leading to reduced resistivity and performance issues in hermetically sealed environments, where conventional solutions like venting or chemical oxygenation are not feasible or effective.
Innovation Solution
A Silver metal window is used to allow Oxygen diffusion within hermetically sealed sensors, maintaining an enriched Oxygen environment and preventing degradation, while ensuring the sensors remain hermetically sealed and protected from external environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor is vented to allow Oxygen exchange, then Oxygen depletion is prevented, but hermetic sealing is lost exposing the sensor to moisture and reactive gases
Solution Approach 1:
The silver oxide layer acts as an internal oxygen reservoir that eliminates the need for external oxygen exchange. It provides oxygen locally within the sealed environment, preventing the need to compromise hermetic sealing while maintaining adequate oxygen levels for piezoelectric element stability.
Solution Approach 2:
The hermetic seal creates a controlled, inert environment that protects the piezoelectric element from harmful external substances. Combined with the internal silver oxide oxygen source, this approach maintains a stable atmosphere without requiring connection to the external environment.
2Reliability
If chemical oxygenation is used to maintain Oxygen levels, then Oxygen depletion is prevented, but device complexity and potential contamination increase
Solution Approach 1:
The silver oxide layer serves itself as the oxygen source, slowly decomposing to release oxygen without requiring external control systems. This self-service approach eliminates complex chemical oxygenation systems while maintaining adequate oxygen levels throughout the sensor's operational life.
Solution Approach 2:
The silver oxide layer is a simple, inexpensive material that is consumed over time to provide oxygen. Rather than using complex, expensive chemical oxygenation systems, this approach uses a simple sacrificial oxygen source that gradually depletes but provides reliable oxygen availability throughout its service life.
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 Silver window maintains the electrical and mechanical properties of piezoelectric materials at high temperatures, enhancing sensor longevity and performance by regulating Oxygen equilibrium, thus preventing resistivity drops and noise issues associated with Oxygen depletion.
Implementation Method 1
A first embodiment of the invention shows a hermetically sealed accelerometer with a cap made partially or entirely in Silver metal, which allows to diffuse Oxygen through it
Implementation Method 2
Conventional piezoelectric accelerometers include a piezoelectric element, made with piezoelectric crystals or ceramic materials, that responds to stimuli from mechanical stresses exerted on their surfaces
Data Source
AI summary
This invention is for a hermetic piezoelectric accelerometer sensor that can operates at high temperatures without the degradation observed on the piezoelectric elements, due to Oxygen depletion of the piezoelectric materials, when they are exposed to high temperatures, in reducing atmospheres, or low partial Oxygen pressure, inside a sealed housing. When a piezoelectric element loses Oxygen, becomes more electrically conductive, and this severe loss in resistivity, exacerbated with the increase of the temperature, makes the sensor inoperable, unreliable, or with permanent damage. The accelerometer of this invention operates effectively over a wide range of temperatures, including high temperatures above 1600° F., depending of the piezoelectric element used on the construction. The housing of the accelerometer uses a small section of metal made with Silver (or Silver alloys) to allow Oxygen diffusion through the metal, when it is exposed to high temperature. This permits that the construction of the accelerometer housing, can be sealed hermetically; and the piezoelectric elements of the sensor have increased lifetime, with enough partial pressure of Oxygen inside the housing.