Optical Gas Pressure Measurement Using LED Absorption Spectroscopy
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Solution Overview
Problem
Existing methods for optical pressure measurement in closed containers are complex, expensive, and unsuitable for industrial use due to the need for precise control of lasers and limited measuring range, making them impractical for automation and industrial applications.
Innovation Solution
A method using a radiator emitting a continuous spectrum with at least one absorption line of the gas, where the transmitted radiation's intensity in a overlapping wavelength range is measured to determine gas pressure, eliminating the need for spectral analysis and modulation, and utilizing a thermal radiator or light-emitting diode for robust and cost-effective measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser with longitudinal mode control is used for optical pressure measurement, then measurement precision is improved, but device complexity and cost increase due to precise control of operating current and temperature
Solution Approach 1:
The patent replaces expensive, complex lasers with inexpensive light-emitting diodes (LEDs) as the radiation source. LEDs are significantly cheaper and simpler to operate while still providing sufficient spectral output for absorption line detection. This substitution directly reduces device complexity and cost while maintaining measurement precision through the use of a wavelength-tunable LED system combined with spectral analysis.
Solution Approach 2:
The patent employs wavelength modulation of the LED radiation source to scan through the absorption spectrum of the gas. By periodically modulating the wavelength and analyzing the absorption spectrum at different wavelengths, the system can determine pressure without requiring the precise longitudinal mode control needed by traditional lasers. This parameter change approach simplifies the control system while maintaining measurement accuracy.
2Measurement precision
If absorption line measurement is performed with high precision, then measurement accuracy is improved, but productivity decreases due to long measurement time
Solution Approach 1:
The patent uses periodic wavelength modulation of the LED source to rapidly scan through the absorption spectrum. By modulating the wavelength at a specific frequency and using synchronous detection, the system can quickly acquire absorption line data and determine pressure. This periodic action enables fast measurements suitable for automation while maintaining high precision through spectral analysis of the modulated signal.
Solution Approach 2:
The patent employs pre-calculated absorption spectra and lookup tables that store the relationship between absorption characteristics and pressure values. During measurement, the system compares the measured absorption spectrum against these pre-computed reference spectra to rapidly determine pressure without requiring time-consuming iterative calculations. This preliminary preparation of reference data significantly speeds up the measurement process while maintaining accuracy.
3Adaptability or versatility
If absorption lines are measured at high pressure, then measuring range is extended, but measurement precision deteriorates due to line broadening and merging
Solution Approach 1:
The patent transitions from measuring a single absorption line to analyzing the entire absorption spectrum across multiple wavelengths. By measuring absorption characteristics over a broad spectral range and analyzing the overall spectral shape rather than individual lines, the system can determine pressure even when individual absorption lines broaden and merge at high pressures. This dimensional extension from single-line to multi-line spectral analysis maintains precision across a wider pressure range.
Solution Approach 2:
The patent develops a universal measurement method that works across a wide pressure range by using the complete absorption spectrum rather than pressure-specific absorption lines. The evaluation algorithm is designed to extract pressure information from spectral characteristics that remain distinguishable across different pressure conditions, making the system universally applicable from low to high pressures without requiring pressure-specific calibration or measurement techniques.
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 a simple, robust, and cost-effective method for measuring gas pressure, suitable for industrial use, with improved accuracy and a larger measuring range, enabling faster and more reliable measurements, particularly for carbon dioxide in beverage bottles and vacuum-sealed containers.
Implementation Method 1
radiation from a radiator is directed through the container and the transmitted radiation is measured in a detector. The radiation from the radiator has at least a first wavelength range in which the radiation is absorbed by the gas
Implementation Method 2
The radiation from the radiator has at least a first wavelength range in which the radiation is absorbed by the gas
Data Source
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AI summary
The invention relates to a method for optical pressure measurement of a gas in a closed container by deflecting radiation of an emitter through the container and measuring the transmitted radiation by means of a detector, wherein the radiation of the emitter covers at least one first wavelength range, in which an absorption of the radiation by the gas takes place, the intensity of the transmitted radiation is detected by the detector in a second wavelength range, wherein the second wavelength range at least partially overlaps the first wavelength range, and a cumulative intensity of the detected radiation in the second wavelength range is associated with a pressure of the gas.