Multilayer Strain Gauge for High Gauge Factor and Stable TCR
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Solution Overview
Problem
Existing strain gauges face challenges in achieving a gauge factor of 10 or more while being insusceptible to temperature changes, as they often have unstable resistance coefficients due to variations in production processes.
Innovation Solution
A strain gauge with a multilayer structure comprising a Cr—Fe alloy first layer and a Cr-M alloy or Cr second layer, where both layers have a bcc structure, allowing for a gauge factor of 10 or more and a temperature coefficient of resistance within ±1000 ppm/°C, achieved by adjusting the thickness balance without requiring a diffusion barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin-film resistor with chromium and controlled orientation is used to achieve high gauge factor, then the gauge factor can be 10 or more, but the temperature coefficient of resistance becomes highly sensitive to production process variations
Solution Approach 1:
The patent uses a multilayer composite structure consisting of a Cr-Fe alloy layer and a Cr-M alloy layer. This composite material approach allows the first layer to provide high gauge factor through controlled chromium orientation, while the second layer compensates for temperature effects, achieving both high measurement precision and temperature stability simultaneously.
Solution Approach 2:
The patent changes the compositional parameters by introducing iron into the chromium alloy and selecting specific Cr-M alloys for the second layer. By adjusting the composition ratios and controlling the crystal orientation parameters during fabrication, the patent achieves a gauge factor of 10 or more while maintaining temperature coefficient stability within ±1000 ppm/°C.
2Measurement precision
If heat treatment is optimized to control chromium orientation for high gauge factor, then the gauge factor increases, but the production process becomes more complex and less stable
Solution Approach 1:
Instead of relying solely on complex heat treatment processes to achieve both high gauge factor and stability, the patent uses a composite material approach where the multilayer structure inherently provides the desired properties. This reduces production process complexity while maintaining high measurement precision.
3Reliability
If a multilayer structure with positive and negative temperature coefficient materials is used, then temperature stability is improved, but the gauge factor remains below 5
Solution Approach 1:
The patent changes the material parameters by using Cr-Fe alloy with specific composition ratios and controlling the crystal orientation to achieve (110) bcc structure. This allows the first layer to provide a gauge factor of 10 or more while the second layer provides positive temperature coefficient to compensate for the negative TCR of the first layer, achieving both high gauge factor and temperature stability.
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 strain gauge achieves a stable gauge factor of 10 or more and temperature coefficient of resistance within ±1000 ppm/°C, ensuring high accuracy and insensitivity to temperature fluctuations.
Implementation Method 1
a strain gauge including a strain resistor having a multilayer structure including a first layer composed of a Cr—Fe alloy and a second layer composed of Cr or a Cr-M alloy of Cr and M
Implementation Method 2
a first layer composed of a Cr—Fe alloy and a second layer composed of Cr or a Cr-M alloy... a gauge factor Gf of 10 or more and a temperature coefficient of resistance TCR in the range of ±1000 ppm/° C.
Data Source
AI summary
A strain gauge includes a strain resistor having a multilayer structure including a first layer composed of a Cr—Fe alloy and a second layer composed of Cr or a Cr-M alloy of Cr and M, M being at least one element selected from the group consisting of Fe, Nb, Mo, Ta, and W. The first layer and the second layer may each have a bcc structure. The amount of Fe added in the Cr—Fe alloy constituting the first layer may be 0.8 at. % or more and 11.2 at. % or less. When the second layer is composed of a Cr-M alloy but with M being other than Fe, the amount of M added may be more than 0 at. % and 7.7 at. % or less.