Resistance Thermometer Sensor Assembly Cover Layer
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Solution Overview
Problem
Resistance thermometers suffer from alterations and damage at the boundary layer due to differing thermal coefficients of expansion between the cover layer and the measuring structure, leading to unreliable temperature measurements over time.
Innovation Solution
A sensor assembly with a cover layer composed of alternating layers of aluminum oxide and magnesium oxide, where the thermal coefficient of expansion is adapted to match that of the platinum measuring structure, minimizing strain and damage through a layered structure produced by sputter deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer cover layer is used, then the structure is simple, but the thermal coefficient of expansion mismatch causes alterations and damage at the boundary layer
Solution Approach 1:
The cover layer is divided into multiple sub-layers (first cover layer and second cover layer) with different materials and thermal expansion coefficients. This segmentation allows each layer to handle different aspects of thermal stress, preventing boundary layer damage while maintaining structural simplicity.
Solution Approach 2:
The patent uses a composite cover layer structure combining materials with different thermal expansion coefficients (e.g., platinum-based measuring structure with ceramic or metallic cover layers). This composite approach creates a gradient that accommodates thermal expansion differences, eliminating the mismatch problem while keeping the overall design straightforward.
2Object-affected harmful factors
If the cover layer material is chosen for protection, then protection against external influences is improved, but the thermal expansion mismatch causes strain and damage
Solution Approach 1:
The patent adjusts the thermal expansion coefficient parameter of the cover layer by selecting specific materials or creating composite structures. This parameter optimization ensures the cover layer provides adequate protection while matching the thermal expansion characteristics of the measuring structure, preventing strain and boundary layer damage.
3Object-affected harmful factors
If a thick cover layer is used for better protection, then protection is improved, but thermal stress and expansion mismatch are amplified
Solution Approach 1:
Instead of using a single thick cover layer, the patent segments the protective layer into multiple thinner sub-layers. This segmentation reduces the thermal stress accumulated in each individual layer while maintaining the overall protection level, as each thin layer can better accommodate thermal expansion without generating excessive stress.
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 solution provides stable and reliable long-term temperature measurements by minimizing thermal expansion mismatches, reducing the risk of damage and maintaining measurement accuracy, while also offering better protection against external influences.
Implementation Method 1
The first and second layers are disposed over one another such that a thermal coefficient of expansion of the cover layer is adapted to a thermal coefficient of expansion of the measuring structure
Implementation Method 2
a layered structure produced by sputter deposition
Data Source
AI summary
A sensor assembly for a resistance thermometer is disclosed. The sensor assembly comprises a substrate, a measuring structure disposed on the substrate, and a cover layer disposed on the measuring structure. The cover layer has a plurality of first layers formed of a first material and a plurality of second layers formed of a second material. The first and second layers are disposed over one another such that a thermal coefficient of expansion of the cover layer is adapted to a thermal coefficient of expansion of the measuring structure.