NDIR Glucose Detection in Liquids via Interference Calibration
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Solution Overview
Problem
Non-Dispersive Infra-Red (NDIR) measurement techniques face debilitating measurement noise due to scattering when detecting molecules in liquids, as the higher molecular density in liquids interferes with the accuracy of concentration measurements, and existing methods struggle to effectively quantify the impact of interfering molecules on calibration curves.
Innovation Solution
The technique involves pulsing infrared radiation from signal, interference, and reference sources into a multiplexer, creating a collimated beam that penetrates a liquid sample, with signal processing to obtain average ratio values to calculate the concentration of targeted molecules by using a chosen calibration curve, which is validated and rectified to account for interfering molecules, ensuring accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NDIR measurement is used to detect molecules in liquids, then the detection capability is achieved, but scattering noise significantly increases due to higher molecular density
Solution Approach 1:
The patent applies periodic pulsing of infrared radiation from signal, interference, and reference sources at a preselected frequency. This periodic action allows the system to capture multiple measurements over time and compute average ratio values, which reduces the impact of random scattering noise while maintaining the ability to detect molecular concentrations in liquids
Solution Approach 2:
The system uses feedback by measuring absorption at multiple wavelengths (signal wavelength within absorption band of targeted molecule, interference wavelength within absorption band of interfering molecule, and reference wavelength outside both absorption bands) and using signal processing to calculate average ratio values. This feedback mechanism allows the system to compensate for scattering effects and quantify the impact of interfering molecules on calibration curves
2Reliability
If conventional NDIR method is used without accounting for interfering molecules, then the measurement process is simple, but the calibration curve becomes invalid due to interference from other absorbing molecules
Solution Approach 1:
The patent segments the absorption measurement into three distinct wavelength components: signal wavelength (within absorption band of targeted molecule M), interference wavelength (within absorption band of interfering molecule MJ), and reference wavelength (outside both absorption bands). This segmentation allows the system to separately quantify the absorption contributions from targeted molecules and interfering molecules, enabling valid calibration curves even in the presence of interferers
Solution Approach 2:
The patent introduces an intermediary interference radiation source that emits at the interference wavelength. This intermediary source allows the system to measure the absorption contribution of interfering molecules separately, which then can be used to correct the calibration curve and account for their impact on the measurement of targeted molecules
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 method significantly reduces scattering noise and ensures the validity of concentration measurements by accounting for interfering molecules, providing precise detection of targeted molecules in liquid samples.
Implementation Method 1
Non-Dispersive Infra-Red (NDIR) is a common and excellent measurement technique for detecting gases in the atmosphere. NDIR sensors utilize the principle that various gas molecules exhibit substantial absorption at specific wavelengths in the infrared radiation spectrum.
Implementation Method 2
The signal source emits radiation at a signal wavelength which is within a first absorption band of the targeted molecule M, the interference source emits radiation at an interference wavelength which is within a second absorption band of said at least one interfering molecule MJ
Implementation Method 3
For detecting molecules in liquids, the NDIR measurement method, which works well in the gaseous phase where the molecular density is low, encounters debilitating measurement noise caused by scattering because of the much higher molecular density in liquids.
Data Source
AI summary
For determining concentration of targeted molecules MG in a liquid sample admixed with interfering molecules MJ which overlap their absorption band, a special NDIR sampling and calibration technique is employed. Besides the signal source, a reference and one or more interference sources are added. The selection of the wavelength for the interference sources enables its measured transmittance value to be used for deciding the validity of the calibration curve for molecules MG in the liquid sample. This value can further be used to adjust the calibration curve via a parameter linking the transmittances measured at the signal and interference wavelength channels in order to assure its validity.