NMR Calibration via Relaxation Time Distribution
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Solution Overview
Problem
Current methods for determining material moisture, such as the Darr drying cabinet method and NMR-based techniques, are limited in their ability to provide rapid, on-site, non-destructive, and absolute measurements, requiring complex calibration processes that take several weeks and are not suitable for field use.
Innovation Solution
A method for determining a material-specific calibration specification for NMR measuring devices, involving the creation of a functional relationship between NMR measurement variables and moisture content, using relaxation curves and approximated relaxation time distributions to accelerate calibration and enable precise moisture determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a material-specific calibration protocol is established through complex preliminary measurements at defined moisture levels, then measurement precision is improved, but loss of time increases significantly as the procedure takes several weeks
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing relaxation time distributions for multiple moisture contents based on a single reference measurement. Instead of performing time-consuming measurements at each moisture level during calibration, the system pre-computes the entire calibration curve from one reference relaxation curve, dramatically reducing calibration time while maintaining measurement precision
Solution Approach 2:
The patent utilizes parameter changes by varying the moisture content parameter θ in the relaxation time distribution calculation. By mathematically transforming the reference relaxation time distribution ρ(θ_ref) to obtain approximate distributions ρ(θ_i) for different moisture contents, the system generates a complete calibration curve through parameter transformation rather than repeated physical measurements
2Measurement precision
If the drying oven method is used as a reference method for moisture determination, then measurement precision is improved, but ease of operation deteriorates as it is limited to laboratory operation
Solution Approach 1:
The patent replaces the mechanical/thermal drying oven system with an NMR-based measurement system. Instead of physically drying samples in an oven to determine moisture content, the system uses nuclear magnetic resonance to directly measure moisture content non-destructively, enabling field applications while maintaining accuracy through the established calibration procedure
Solution Approach 2:
The patent creates a mathematical model (calibration curve) that copies the relationship between NMR signals and moisture content established by the drying oven method. By deriving the calibration function from reference measurements and storing it for future use, the system replicates the accuracy of laboratory methods while enabling rapid field measurements
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 the time required for calibration from weeks to hours, allowing for rapid and accurate moisture measurement of various materials, enabling reliable on-site assessments without the need for extensive laboratory procedures.
Implementation Method 1
NMR measurement quantity A of a material under investigation, as determined by an NMR measuring instrument... based on a measurement of nuclear spin effects in the material under investigation
Implementation Method 2
the precession (Larmor precession) of the nuclear spins of the atomic nuclei in the material under investigation around the magnetic field lines
Implementation Method 3
a relaxation curve s(t,θ ref) of the material... Determining a relaxation time distribution ρ(θ ref) from the provided relaxation curve
Data Source
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AI summary
Disclosed is a method for determining a calibration specification, said calibration specification specifying a functional correlation between an NMR measurement variable A, which can be determined using an NMR measuring device (10), for a material (34) to be analysed and a humidity θ contained in a material (34) to be analysed. According to the invention, the method comprises at least the following method steps: • provision of a relaxation curve (t,θref) of the material (34) having a known humidity θref ; • determination of a relaxation time distribution ρ(θref) from the relaxation curve s(t,θref) provided; • determination of an approximate relaxation time distribution ρ(θi) relative to at least one humidity θi, where θi < θref ; • reconstruction of a relaxation curve s(t,θi) from the approximate relaxation time distribution ρ(θi); • determination of an expected NMR measurement variable A, from the reconstructed relaxation curve s(t,θi) for the humidity θi; • determination of the calibration specification as a function θ(A) of the humidity θ, in accordance with the determinable NMR measurement variable A. Also disclosed is a method for determining an absolute humidity θ of a material (34) to be analysed, using an NMR measuring device (10), the absolute humidity θ being determined using the functional correlation specified in the calibration specification. Finally, an NMR measuring device (10) for carrying out the method is disclosed.