Accelerometer Proof Mass CTE Matching for Bias Reduction
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Solution Overview
Problem
Accelerometers experience bias and reduced accuracy due to differing coefficients of thermal expansion (CTE) between the proof mass element and non-moving members, leading to thermally-induced strain that is misinterpreted as acceleration signals.
Innovation Solution
Selecting or manufacturing the proof mass element with a CTE value within a threshold range of the non-moving members, typically within 30% of their CTE value, to ensure similar expansion and contraction rates, reducing strain and bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the proof mass element is made from a material with a CTE value significantly different from the non-moving members, then the accelerometer can be manufactured with easier material selection and fabrication, but thermally-induced strain is generated at interfaces leading to bias and reduced measurement accuracy
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the CTE values of materials used for the proof mass element and non-moving members. By modifying the material composition and thermal expansion parameters to fall within specific ranges (CTE values within 30% of each other), the invention reduces thermally-induced strain at interfaces while maintaining manufacturing feasibility. This involves changing the physical parameters of the materials to achieve thermal compatibility without sacrificing ease of manufacture.
Solution Approach 2:
The patent applies homogeneity by ensuring that the proof mass element and non-moving members have matched thermal expansion characteristics. By making the CTE values of these components homogeneous (within 30% of each other), the invention creates a thermally compatible system where all components expand and contract at similar rates, minimizing differential strain and improving measurement accuracy across temperature variations.
2Adaptability or versatility
If the proof mass element and non-moving members have different CTE values, then different materials can be used to optimize individual component performance, but strain is induced at interfaces when temperature changes occur, causing bias in the accelerometer output
Solution Approach 1:
The patent applies parameter changes by establishing specific CTE value ranges for the proof mass element and non-moving members. By modifying the thermal expansion parameters to fall within 30% of each other, the invention maintains material selection flexibility while ensuring reliable operation. This involves changing the physical parameters of the materials to achieve thermal compatibility, allowing different materials to be used for optimizing individual component performance without inducing harmful strain.
3Ease of manufacture
If materials with vastly different CTE values are used for the proof mass element and housing, then each component can be optimized for its specific function, but thermally-induced strain misinterpreted as acceleration signals occurs, reducing measurement accuracy
Solution Approach 1:
The patent applies parameter changes by adjusting the CTE values of the proof mass element and housing materials to be within 30% of each other. This modification allows each component to be optimized for its specific function while preventing thermally-induced strain that would be misinterpreted as acceleration signals. The invention changes the thermal expansion parameters to achieve both component optimization and measurement accuracy.
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
This approach minimizes thermally-induced strain, enhancing the accuracy and reducing bias in accelerometer output by maintaining consistent expansion and contraction rates between the proof mass and non-moving members.
Implementation Method 1
the proof mass element and the non-moving member(s) may expand and/or contract at different rates when the accelerometer is exposed to changes in temperature
Data Source
AI summary
An accelerometer system including: a housing comprising a first portion and a second portion, the housing has a first coefficient of thermal expansion (CTE) value; and a proof mass element disposed between the first portion and the second portion of the housing, wherein a first surface of the proof mass element contacts the first portion and a second surface of the proof mass element contacts the second portion, the proof mass element having a second CTE value, the second CTE value being within 30% of the first CTE value.