Optical Sensor Calibration Validation Using Isosbestic Wavelengths
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Solution Overview
Problem
Existing sensors used for continuous measurement of analytes, particularly in clinical and food monitoring, suffer from drift issues, leading to inaccurate readings over time, and there is a lack of effective methods to validate the calibration of these sensors, which can result in dangerous therapeutic decisions if errors are not detected.
Innovation Solution
A method involving three or more measurements at different wavelengths, including an isosbestic wavelength, is used to determine if the sensor readings are consistent with a calibrated relationship, allowing detection of drift or error, and outputting a warning when calibration is invalid, thus reducing the need for unnecessary recalibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If sensor is used for continuous measurement over prolonged periods, then continuous monitoring capability is improved, but measurement accuracy deteriorates due to drift
Solution Approach 1:
The patent implements a feedback mechanism by measuring the optical property at the isosbestic wavelength and comparing it against stored reference values. When the measured isosbestic value deviates from the reference, the system generates a warning signal indicating calibration drift, allowing operators to recalibrate the sensor without interrupting continuous monitoring. This feedback loop maintains measurement accuracy throughout prolonged operation.
Solution Approach 2:
The patent performs preliminary calibration measurements at multiple wavelengths including the isosbestic wavelength during system setup. These preliminary measurements establish reference values that are stored for later comparison. By performing this calibration action in advance, the system is prepared to detect and respond to drift conditions during continuous operation, resolving the contradiction between prolonged operation and maintaining accuracy.
2Measurement precision
If frequent recalibration is performed to maintain accuracy, then measurement precision is improved, but operational complexity and time loss increase
Solution Approach 1:
The system continuously monitors the isosbestic wavelength measurement and compares it against stored reference values. Only when drift is detected through this feedback mechanism does the system trigger a recalibration warning. This eliminates the need for frequent manual recalibration operations, reducing time loss while maintaining accuracy through condition-based recalibration rather than time-based recalibration.
Solution Approach 2:
The system performs self-diagnosis by automatically measuring the isosbestic wavelength and comparing it against stored references to detect calibration drift. This self-service capability allows the system to monitor its own calibration status without requiring external intervention, reducing the time and complexity associated with manual calibration checks and operations.
3Reliability
If multiple wavelength measurements are made to detect drift, then reliability of calibration validation is improved, but device complexity increases
Solution Approach 1:
The patent segments the optical measurement into distinct wavelength components, specifically measuring at the isosbestic wavelength separately from other analytical wavelengths. This segmentation allows the system to isolate and monitor calibration status using a dedicated measurement channel, improving reliability without requiring complex multi-wavelength simultaneous measurement systems.
Solution Approach 2:
The isosbestic wavelength measurement serves multiple functions: it acts as a calibration reference, a drift detection mechanism, and a quality control indicator. By making the measurement system multi-functional, the patent improves calibration validation reliability without proportionally increasing device complexity, as the same measurement infrastructure serves multiple purposes.
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
This approach provides confidence in the validity of sensor readings by detecting drift or error, ensuring accurate measurements and reducing the burden of frequent recalibrations, thereby enhancing safety and reliability in clinical and food monitoring applications.
Implementation Method 1
a sensing substance having an optical property with a spectrum which varies with the concentration of the analyte in the sample
Implementation Method 2
measuring an optical property of the sensing substance while it is exposed to a sample containing the analyte
Data Source
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Figure 2
Figure 3~4
AI summary
There is provided a method of validating a calibration (40) of a sensor (4) represented by a calibrated relationship between concentration of an analyte in a sample and measurements from a sensor (4) of an optical property of a sensing substance (9), wherein the optical property of the sensing substance has a spectrum that varies with the concentration of the analyte in the sample, and the spectrum has an isosbestic wavelength (λi) at which the optical property does not vary with concentration of the analyte, the method comprising making measurements of the optical property (S10) at three or more wavelengths of light while the sensing substance (9) is exposed to the sample, determining whether the measurements of the optical property are inconsistent (S16) with the calibrated relationship, and outputting a warning signal (S18) in response to the measurements of the optical property being inconsistent with the calibrated relationship.