Inductive Pick-off Accelerometer for High-Temperature Operation
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Solution Overview
Problem
Conventional accelerometers fail to operate effectively in harsh environments with ambient temperatures up to 1000°C due to limitations in temperature resistance and high-frequency signal transmission, leading to errors and difficulties in electrical connections.
Innovation Solution
An open-loop, dual-axis accelerometer design utilizing an inductive pick-off system with a near field resonant inductive coupling mechanism, featuring a monolithic structure of three bonded wafers made from high-temperature materials, which operates in the megahertz frequency range to reduce errors and eliminate the need for lengthy high-temperature cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional capacitive pick-off is used in accelerometer, then the structure is simple and manufacturing is easy, but the temperature resistance is limited and high-frequency signal transmission causes errors
Solution Approach 1:
The patent replaces the conventional capacitive pick-off (electrical field-based) with an inductive pick-off system using magnetic fields. The inductive pick-off includes a drive coil generating a magnetic field and sense coils detecting changes in magnetic flux caused by proof mass displacement. This substitution enables operation in high-temperature environments (up to 1000°C) where capacitive systems fail, while the magnetic coupling provides stable high-frequency signal transmission without the errors affecting capacitive systems.
Solution Approach 2:
The patent changes the operating frequency parameter to the megahertz range, which reduces errors in high-temperature environments. The inductive pick-off system is specifically designed to operate at these frequencies, maintaining signal integrity where conventional lower-frequency capacitive systems experience degradation. The magnetic field-based detection maintains consistent coupling characteristics across the operating temperature range and frequency band.
2Reliability
If lengthy high-temperature cables are used for signal transmission, then connections can be made in harsh environments, but errors increase and the system becomes complex
Solution Approach 1:
The patent introduces magnetic field coupling as an intermediary between the proof mass and the external reading system. The inductive pick-off system uses magnetic flux coupling through the wafer structure, eliminating the need for lengthy physical cable connections that traverse harsh thermal environments. This field-based intermediary provides reliable signal transmission without the mechanical connection problems that plague high-temperature cable systems.
3Adaptability or versatility
If the accelerometer operates in harsh environments with temperatures up to 1000°C, then high-temperature applications are enabled, but conventional materials and electrical connections fail
Solution Approach 1:
The patent employs a composite structure consisting of three bonded wafers: a support wafer, a proof mass wafer, and a cap wafer. These wafers are made from high-temperature-resistant materials capable of withstanding 1000°C environments. The bonding creates a hermetically sealed structure that protects internal components while maintaining the high-temperature operation capability. This composite approach enables harsh environment operation while using established wafer fabrication and bonding techniques.
4Stability of the object's composition
If inductive pick-off with near field resonant inductive coupling is used, then temperature stability and hermetic sealing are achieved, but the device structure becomes more complex
Solution Approach 1:
The patent merges the inductive pick-off functionality directly into the wafer structure itself. The drive coil and sense coils are fabricated as part of the wafer assembly, with magnetic flux paths integrated through the wafer layers. This integration eliminates separate pick-off components and reduces overall device complexity while achieving the desired temperature stability and hermetic sealing. The inductive coupling mechanism is embedded in the structure rather than added as a separate subsystem.
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 design provides high temperature stability, hermetic sealing, and immunity to in-plane rotation and tilting, enabling accurate acceleration measurements in extreme environments without significant temperature sensitivity or cross-talk issues.
Implementation Method 1
The source coil source coil is configured to receive an applied voltage to generate a source current, and transmit a first electromagnetic energy based on the source current. The target coil positioned on a proof mass of the accelerometer is configured to receive a portion of the first electromagnetic energy to generate a target current in the target coil, and transmit a second electromagnetic energy based on the target current. Each of the plurality of pick-off coils configured to receive a portion of the second electromagnetic energy to generate a pick-off voltage signal
Implementation Method 2
The inductive pick-off may operate as a variable transformer using a near field resonant inductive coupling mechanism
Data Source
AI summary
An accelerometer as disclosed herein includes a support wafer, a bottom wafer, a top wafer, and an inductive pick-off. The support wafer may define a plane and may comprise a first side, a second side, and a proof mass. The proof mass may be configured to move in the plane defined by the support wafer. The bottom wafer may comprise a first side and a second side, and the first side may be positioned over the first side of the support wafer. The top wafer may comprise a first side and a second side, and the first side may be positioned over the second side of the support wafer. The inductive pick-off may comprise a near field resonant conductive coupling mechanism and may be configured to output a signal indicative of an amount of displacement of the proof mass to electronics.