Symmetric Strain Gauge Trimming for Force Sensor Bridge Balance
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Solution Overview
Problem
Previous methods for trimming strain gauges to balance resistance values often result in undesirable variations in sensitivity and can cause shifts in gauge placement, leading to errors in force measurement, which are unacceptable in high-precision applications.
Innovation Solution
The solution involves a symmetric trimming approach where tension and compression strain gauge resistors share a common center axis, with trim regions extending along this axis to adjust resistance while maintaining matching resistance values and layout patterns on both sides, ensuring consistent sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional trimming methods are used to adjust resistance values, then resistance matching is achieved, but sensitivity variations and placement shifts occur
Solution Approach 1:
The patent applies asymmetry by positioning trim regions at symmetric locations relative to the gauge's center axis, ensuring that trimming operations on opposite sides produce equal and opposite effects that cancel out placement shifts while maintaining resistance matching. This symmetric asymmetry approach resolves the contradiction by preserving measurement precision while achieving manufacturing precision.
Solution Approach 2:
The patent implements local quality by creating distinct trim regions with specific geometric characteristics at different locations within the strain gauge structure. By localizing trimming operations to specific regions rather than uniformly across the entire gauge, the invention achieves resistance matching without causing global sensitivity variations or placement shifts.
2Reliability
If strain gauges are trimmed to balance bridge resistance, then DC offset is reduced, but sensitivity matching is disrupted
Solution Approach 1:
The patent uses symmetric trim region positioning relative to the gauge center axis to ensure that resistance trimming maintains sensitivity matching. By placing trim regions at symmetric locations, the trimming process affects both tension and compression sides equally, preserving the sensitivity balance required for reliable bridge operation.
Solution Approach 2:
The patent segments the strain gauge into distinct functional regions including active strain-sensitive areas and separate trim regions. This segmentation allows independent optimization of each region's function - the active regions maintain sensitivity while the trim regions enable resistance adjustment without interfering with sensitivity matching.
Data Source
AI summary
A circuit is provided that includes a strain gauge resistor having a center axis and multiple conductor layer segments and a trim region extending along the center axis; wherein a first portion of the strain gauge resistor is located on one side of the center axis and a second portion of the strain gauge resistor is located on an opposite side of the center axis.