Resistance Thermometer Substrate Thermal Expansion Matching
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Solution Overview
Problem
Resistance thermometers with substrates and measuring structures of different thermal expansion coefficients suffer from damage and unreliable measurements due to abrupt temperature changes, leading to measurement inaccuracies over time.
Innovation Solution
A substrate with alternating layers of aluminum oxide and magnesium oxide, or other materials, is designed to match the thermal expansion coefficient of the platinum measuring structure, minimizing boundary region effects and ensuring stable long-term measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a substrate with different thermal coefficient of expansion is used compared to the platinum measuring structure, then the substrate can be manufactured with simpler materials, but the boundary layer between substrate and measuring structure suffers alterations and damage during abrupt temperature changes
Solution Approach 1:
The patent applies parameter changes by carefully selecting the thermal expansion coefficient of the substrate material to match that of platinum. This parameter matching ensures that both materials expand and contract at the same rate during temperature changes, eliminating differential stress at the boundary layer and preventing damage while maintaining measurement reliability.
Solution Approach 2:
The patent employs composite materials by combining the platinum measuring structure with a substrate material that has matched thermal expansion properties. This composite approach allows the substrate to provide mechanical support while experiencing minimal thermal stress at the interface, thus maintaining both ease of manufacture and measurement reliability.
2Ease of manufacture
If a substrate with different thermal coefficient of expansion is used compared to the platinum measuring structure, then the substrate can be produced more economically, but alterations and damage occur at the boundary layer over time
Solution Approach 1:
The patent applies parameter changes by selecting a substrate material with a thermal expansion coefficient matched to platinum. This parameter alignment prevents differential thermal stress accumulation over time, thereby extending the operational lifespan and maintaining measurement accuracy without requiring expensive specialized materials.
Solution Approach 2:
The patent uses composite materials with matched thermal properties to create a durable measurement system. The substrate and platinum measuring structure form a composite where both materials expand and contract uniformly, preventing interface degradation and ensuring long-term measurement reliability while maintaining cost-effectiveness.
3Reliability
If the substrate has a thermal coefficient of expansion matched to platinum, then boundary layer damage is prevented, but the substrate material selection becomes more restricted
Solution Approach 1:
The patent applies parameter changes by identifying and selecting materials with thermal expansion coefficients that match platinum's properties. This parameter matching ensures boundary layer stability during temperature cycling, though it does limit the range of available substrate materials to those with compatible thermal characteristics.
Solution Approach 2:
The patent employs composite materials with specifically selected thermal properties to maintain boundary layer stability. By choosing materials with matched thermal expansion coefficients, the patent achieves reliable measurement while accepting reduced material versatility, as only materials with compatible thermal parameters can be used.
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 substrate provides a stable thermal expansion match to the platinum measuring structure, preventing damage and maintaining accurate temperature measurements across varying temperatures.
Implementation Method 1
The substrate and the measuring structure in known resistance thermometers have different thermal coefficients of expansion. When known resistance thermometers are stressed by abrupt changes in temperature, alterations and damage, which act on the entire measuring structure and falsify the measurement values as a result, can occur at the boundary layer between the substrate and the measuring structure.
Data Source
AI summary
A substrate for a sensor assembly of a resistance thermometer is disclosed. The substrate 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 substrate is approximately equal to the thermal coefficient of expansion of platinum.