MEMS Thermal Sensor Array With Sapphire-Based Drift Correction
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Solution Overview
Problem
Current measurement techniques for high-temperature gas-cooled reactors (HTGRs) lack the refinement to evaluate transient flow structures at a spatial scale useful for mesoscale core design, and there is a need for high spatial resolution measurements in harsh environments, particularly in pebble bed HTGRs, where existing instruments face challenges with calibration drift due to environmental effects.
Innovation Solution
A MEMS thermal sensor array using a dual-sensing platinum resistor encased in a mono-crystalline alpha-alumina (sapphire) substrate, with a Wheatstone bridge circuit, measures temperature via 4-wire ohm resistance and differential strain, allowing self-calibration to mitigate drift by comparing two independent measures of electron mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional measurement techniques are used in HTGRs, then the instruments can operate in high-temperature environments, but they suffer from calibration drift due to environmental effects
Solution Approach 1:
The patent implements a feedback mechanism where the Wheatstone bridge circuit continuously monitors the resistance changes of the platinum resistor and automatically compensates for calibration drift caused by temperature and strain effects. The bridge circuit provides real-time feedback to maintain measurement accuracy despite environmental variations in the HTGR setting.
Solution Approach 2:
The patent utilizes the temperature-dependent resistance characteristics of platinum and the strain-dependent resistance changes in the Wheatstone bridge to detect and compensate for calibration drift. By monitoring changes in electrical resistance parameters, the system can distinguish between actual temperature measurements and drift caused by environmental effects.
2Measurement precision
If high spatial resolution measurements are implemented, then transient flow structures can be evaluated, but the device complexity increases
Solution Approach 1:
The patent divides the measurement system into multiple discrete sensor elements arranged in an array, where each element provides localized temperature measurements. This segmentation enables high spatial resolution mapping of thermal fields and transient flow structures while keeping each individual sensor element relatively simple in design.
Solution Approach 2:
The patent employs a universal sensor design based on platinum resistors with Wheatstone bridge circuits that can be replicated across multiple positions in the HTGR. This multi-functional approach allows the same sensor technology to serve multiple measurement points, reducing overall system complexity while achieving high spatial resolution through array configuration.
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 sensor array provides accurate and durable temperature measurements in extreme environments by actively correcting for calibration drift, ensuring precise data collection in HTGR thermal environments.
Implementation Method 1
measures temperature via 4-wire ohm resistance
Implementation Method 2
differential strain-derived measurement of temperature to the temperature derived from the RTD measurement
Implementation Method 3
differential strain-derived measurement of temperature
Implementation Method 4
electrical traces bonded to the surface of the nonconducting substrate, the electrical traces comprising four meander-lines forming a Wheatstone bridge circuit
Implementation Method 5
nonconducting substrate having a surface aligned with a plane of the substrate and exhibiting an anisotropic coefficient of thermal expansion (CTE) in the plane
Implementation Method 6
anisotropic coefficient of thermal expansion (CTE) in the plane
Data Source
AI summary
A novel high temperature thermal sensing method and device is disclosed that can employ a dual-sensing platinum resistor encased in a mono-crystalline alpha-alumina (sapphire) substrate. The device can comprise four platinum trace elements, oriented with 90° rotational symmetry atop a 1120 oriented crystal lattice substrate. The resistance temperature detectors (RTD) temperature measurement calibration can then be monitored for drift and corrected by comparing the differential strain-derived measurement of temperature to the temperature derived from the RTD measurement. This can allow the device to self-calibrate via comparison of two functionally independent measures of electron mobility and operate in extreme environments which have previously caused RTD sensors to drift from their initial calibration and introduce an undefined measurement error.