Gas Detection System Using Dual Frequency Absorption Measurements
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Solution Overview
Problem
Existing gas detection methods are limited in their ability to accurately measure gas concentrations over a wide range, from very low (less than 1 ppm) to very high (up to 100%) due to absorption line saturation and dependence on the shape of absorption lines.
Innovation Solution
A method combining two absorption measurements: one near the peak absorption frequency for low concentrations and another over a broader frequency interval for higher concentrations, utilizing tunable and fixed bandpass filters to account for line broadening and saturation, allowing for accurate concentration deduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If absorption measurement is made near the peak absorption frequency, then sensitivity at low gas concentrations is improved, but absorption line saturation occurs at high concentrations
Solution Approach 1:
The patent divides the absorption measurement into two separate frequency intervals: a first interval near the peak absorption frequency for measuring low concentrations, and a second interval away from the peak for measuring high concentrations. This segmentation allows each measurement to operate in its optimal range without saturation effects.
Solution Approach 2:
The patent changes the measurement parameter (frequency interval) based on the concentration range being measured. By selecting different frequency intervals appropriate to the expected concentration level, the system maintains measurement accuracy across the full dynamic range from ppm to 100% concentrations.
2Reliability
If absorption measurement is made away from the peak frequency over a wider spectrum, then saturation is avoided at high concentrations, but measurement sensitivity decreases
Solution Approach 1:
The measurement system is segmented into two distinct frequency intervals, each optimized for specific concentration ranges. The first interval captures peak absorption for sensitivity at low concentrations, while the second interval measures off-peak absorption to avoid saturation at high concentrations.
Solution Approach 2:
The patent uses partial absorption measurements at two different frequency intervals rather than attempting to capture the full absorption spectrum in a single measurement. This partial action approach allows each measurement to remain within the linear range appropriate for its target concentration level.
3Device complexity
If a single absorption measurement method is used, then device complexity is reduced, but the measurement range is limited
Solution Approach 1:
The patent creates a universal measurement system that can accurately detect gas concentrations across the entire range from ppm to 100% by implementing multi-functionality through two complementary measurement methods. The system adapts its measurement approach based on the expected concentration range, providing broad versatility.
Solution Approach 2:
The measurement system dynamically selects which frequency interval to use based on the expected concentration range. This dynamic adaptation allows the system to maintain simplicity in operation while achieving broad measurement capability across different concentration scenarios.
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
Enables sensitive and accurate gas concentration measurement across a wide dynamic range by leveraging peak absorption and line broadening effects, reducing ambiguity and saturation issues, and providing a monotonic signal for high concentrations.
Implementation Method 1
the transmission or absorption of radiation passing through a radiation absorbing medium, such as a gas
Implementation Method 2
At very large concentrations, all of the radiation within a small frequency interval near an absorption peak is heavily absorbed. This is called absorption line saturation.
Implementation Method 3
A second absorption measurement is made over a second frequency interval or set of frequency intervals. The second absorption measurement is made to include a contribution from the broadening of the absorption spectrum at higher concentrations.
Data Source
AI summary
A method and apparatus in which a first absorption measurement is made over a first frequency interval or set of frequency intervals including one or more absorptions from a spectral band of interest. The first absorption measurement is ideally selected to be near the frequency of a peak in the absorption spectrum, providing high sensitivity at low gas concentrations. A second absorption measurement is made over a second frequency interval. The second absorption measurement is made to include a contribution from the broadening of the absorption spectrum at higher concentrations. The second absorption measurement provides sensitivity at higher concentrations. The two absorption measurements are then combined to deduce the target sample concentration as the absorption line spectrum changes shape with concentration.