Strain Gauge Barrier Layer for Leakage Current Reduction
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Solution Overview
Problem
Conventional strain gauges experience stability issues due to leakage current when used underwater or in water-splashing environments, particularly those with high gauge factors, leading to variations in output voltage.
Innovation Solution
A strain gauge with a flexible substrate, a resistor made from a film containing Cr, CrN, and Cr2N, and a resin barrier layer with a moisture permeability to thickness ratio of 5:1 or greater, and a thickness of 100 μm or more and 3 mm or less, to reduce leakage current and output voltage variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high gauge factor resistor is used to improve strain detection sensitivity, then measurement precision is improved, but leakage current increases causing output voltage variation and stability deteriorates
Solution Approach 1:
A resin barrier layer is introduced as an intermediary between the resistor and the external environment. This barrier layer selectively blocks moisture and contaminants while allowing the resistor to maintain its high gauge factor properties, thereby preventing leakage current without compromising strain detection sensitivity
Solution Approach 2:
A thin film resin barrier layer is applied over the resistor to provide protection against moisture ingress. The thin film structure maintains flexibility while effectively blocking the pathway for leakage current, solving the stability issue without affecting the resistor's electrical characteristics
2Reliability
If the barrier layer thickness is increased to improve moisture protection, then leakage current reduction is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The resin barrier layer thickness is optimized to a specific range (100-300 μm) where it provides sufficient moisture protection to prevent leakage current while avoiding excessive complexity. This parameter optimization achieves effective protection with a simple single-layer structure
Solution Approach 2:
The barrier layer is applied specifically over the resistor area where moisture protection is most critical, rather than requiring complete encapsulation of the entire strain gauge. This localized approach provides effective leakage current prevention with minimal added complexity
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 described strain gauge effectively reduces the variation of output voltage caused by leakage current, enhancing stability and accuracy, especially in humid environments.
Implementation Method 1
in the barrier layer, a ratio of a moisture permeability (g/m2/24 h) to a thickness (mm) is 5:1 or greater
Data Source
AI summary
A strain gauge includes a flexible substrate; a resistor made from a film containing Cr, CrN, and Cr2N, on one surface of the substrate; and a resin barrier layer covering the resistor, and, in this strain gauge, in the barrier layer, a ratio of a moisture permeability (g/m2/24h) to a thickness (mm) is 5:1 or greater, and the thickness of the barrier layer is 100 μm or more and 3 mm or less.