In Situ Thermometer Calibration Using Curie Point Phase Transitions
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Solution Overview
Problem
Current thermometer calibration methods require removal from the measuring point, leading to disadvantages such as reduced dynamic range and potential damage from escaped fixed point substances, and are prone to aging effects and sensor drift due to the use of reference elements with characteristic curves that are not uniformly linear over the temperature range.
Innovation Solution
An apparatus and method utilizing at least two reference elements with phase transitions of second order, composed of different materials, for in situ calibration and validation of a temperature sensor, allowing for multipoint calibration and validation without the need for additional encapsulation, ensuring stability and accuracy over the entire temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermometer is calibrated in calibration baths or ovens, then calibration accuracy is improved, but the thermometer must be deinstalled from the measuring point, reducing productivity and causing loss of time
Solution Approach 1:
The thermometer performs self-calibration using integrated reference elements (Curie point elements) that provide known reference temperatures. The evaluation unit automatically compares sensor readings against these references and applies corrections without external intervention, enabling the system to calibrate itself while remaining installed at the measuring point.
Solution Approach 2:
The reference elements serve dual purposes: they provide reference temperatures for calibration and simultaneously act as temperature sensors themselves. This multi-functionality eliminates the need for separate calibration equipment and allows continuous calibration at the installation site.
2Ease of operation
If a miniaturized fixed point cell is integrated in the thermometer, then in situ calibration becomes possible, but the dynamic range is reduced and response time increases due to additional encapsulation
Solution Approach 1:
The reference elements utilize phase transitions (Curie point transitions) of ferromagnetic materials to generate stable reference temperatures. These phase transitions occur at specific temperatures and provide well-defined calibration points without requiring encapsulation of fixed point substances, thus maintaining fast response times and full dynamic range.
3Measurement precision
If fixed point substance is used for calibration, then calibration reference is provided, but the substance may escape causing damage or destruction of the thermometer
Solution Approach 1:
Ferromagnetic reference elements undergo solid-state phase transitions at their Curie points without requiring encapsulated substances. The transition from ferromagnetic to paramagnetic state occurs intrinsically within the solid material, eliminating the risk of substance leakage while maintaining stable reference temperatures for calibration.
4Ease of operation
If reference elements with characteristic curves are used for in situ calibration, then aging effects and sensor drift occur due to non-uniform and non-linear characteristic curves
Solution Approach 1:
The Curie point phase transitions of ferromagnetic materials occur at sharply defined temperatures with well-characterized transition points. These transitions provide stable and reproducible reference temperatures that are not subject to aging effects or drift, as the Curie point is a fundamental material property that remains constant over time.
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
Enables precise and reproducible calibration and validation of temperature sensors across their entire range, reducing susceptibility to errors and maintaining response speed to temperature changes, while eliminating the need for separate encapsulation and minimizing aging effects.
Implementation Method 1
the first reference element is composed at least partially of a first material, in the case of which at least one phase transition of at least second order occurs at at least a first predetermined phase transition temperature
Implementation Method 2
the second reference element is composed at least partially of a second material, in the case of which at least one phase transition of at least second order occurs at at least a second predetermined phase transition temperature
Data Source
AI summary
An apparatus for determining and/or monitoring temperature of a medium, comprising at least one temperature sensor and at least two reference elements for in situ calibration and/or validation of the temperature sensor, wherein the first reference element is composed at least partially of a first material, in the case of which at least one phase transition of at least second order occurs at least a first predetermined phase transition temperature in the temperature range relevant for calibration of the temperature sensor, wherein the second reference element is composed at least partially of a second material, in the case of which at least one phase transition of at least second order occurs at least a second predetermined phase transition temperature in the range relevant for calibration of the temperature sensor, and wherein the at least two reference elements are contacted via exactly two connection wires.