Accelerometer Proof Mass CTE Matching for Bias Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Accelerometers experience bias due to differing coefficients of thermal expansion (CTE) between the proof mass element and non-moving members, leading to inaccurate acceleration measurements due to thermally-induced strain.
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 and non-moving members are made of materials with different CTE values, then the accelerometer can be manufactured with easier material selection and assembly, but thermally-induced strain occurs at interfaces leading to bias and reduced measurement accuracy
Solution Approach 1:
The patent applies homogeneity by selecting materials for the proof mass element and non-moving members that have similar or matched coefficients of thermal expansion (CTE). This ensures that all components expand and contract at similar rates during temperature changes, preventing differential thermal expansion. The result is reduced thermally-induced strain at interfaces, eliminating bias in acceleration measurements while maintaining ease of manufacture through systematic material selection criteria.
2Ease of manufacture
If the proof mass element and non-moving members have different CTE values, then manufacturing and assembly become simpler, but the accelerometer exhibits bias due to thermally-induced strain at interfaces
Solution Approach 1:
The patent applies parameter changes by systematically selecting and controlling the coefficient of thermal expansion (CTE) parameter of materials used in the accelerometer components. By choosing materials with matched CTE values for the proof mass element and non-moving members, the patent ensures that thermal expansion parameters are harmonized across components. This eliminates differential expansion behavior, preventing bias generation while maintaining simple assembly procedures.
3Adaptability or versatility
If materials with different CTE values are used for proof mass element and non-moving members, then component fabrication becomes more flexible, but strain at interfaces mimics acceleration signals causing bias
Solution Approach 1:
The patent applies homogeneity by establishing material selection criteria that require the proof mass element and non-moving members to have similar CTE values. This creates a homogeneous thermal expansion behavior across all components, ensuring they respond uniformly to temperature changes. The uniform response prevents spurious strain signals that would otherwise be misinterpreted as acceleration, thereby maintaining measurement precision while preserving material selection flexibility within the matched-CTE constraint.
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
Reduces thermally-induced strain and improves the accuracy of acceleration measurements 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
Implementation Method 2
The deflection by the proof mass element may cause the distance (e.g., a capacitive gap) between capacitance plates on the proof mass element and non-moving members to vary. This variance in the capacitive gap causes a change in the capacitance of the capacitive elements, which is representative of the displacement of the proof mass along a sensitive axis.
Data Source
Figure 1
Figure 2
Figure 3
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.