Gas Modulation Valve for Wide Range Infrared Gas Detection
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Solution Overview
Problem
Existing gas analyzers face challenges in simultaneously detecting low and high concentrations of target gases due to saturation phenomena, where long optical paths are required for low concentration sensitivity but lead to difficulty in distinguishing between high concentrations and ambient levels, and switching between sample and reference gas inlets is not effective for both ranges.
Innovation Solution
Adjusting the duty cycle of the gas modulation valve to create a virtual short path by shortening the sample gas time period relative to the reference gas time period, allowing for multiple short gas pulses and diluting the sample gas, thereby avoiding saturation and enabling analysis across a wide concentration range without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long optical path is used in the gas analyzer, then sensitivity for low gas concentrations is improved, but the ability to detect high gas concentrations deteriorates due to saturation
Solution Approach 1:
The patent applies dynamics by making the optical path length variable rather than fixed. The gas modulation valve dynamically adjusts the effective optical path by alternating between connecting the sample gas inlet and reference gas inlet to the measurement section. This allows the system to adapt the optical path length based on the concentration range being measured, resolving the contradiction between needing a long path for low concentration sensitivity and a short path for high concentration detection.
Solution Approach 2:
The patent changes the parameter of optical path length by using gas modulation to effectively vary the path length. By modulating the gas flow and alternating between sample and reference gas connections, the system creates different effective optical path conditions. This parameter change enables the same measurement section to operate in different detection modes, allowing both low and high concentration measurements without saturation.
2Measurement precision
If gas modulation valve switches between sample and reference gas inlets, then signal-to-noise ratio is enhanced, but detection of both low and high concentrations simultaneously becomes difficult
Solution Approach 1:
The patent uses periodic action through gas modulation where the valve alternates between connecting sample gas and reference gas to the measurement section at a specific frequency. This periodic switching creates a modulated signal that enhances the signal-to-noise ratio through synchronous detection. The periodic nature allows the system to maintain high sensitivity while handling varying concentration ranges by adjusting the modulation parameters and duty cycle.
Solution Approach 2:
The system dynamically adjusts the duty cycle of the gas modulation valve to optimize detection for different concentration ranges. By varying the proportion of time spent sampling versus reference measurement, the system can adapt to both low and high concentrations while maintaining enhanced signal-to-noise ratio through the modulation technique.
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 enhances the capability of gas analyzers to accurately detect both low and high gas concentrations by preventing saturation and improving signal linearity, allowing for precise measurement over an extended range without the need for separate cuvettes or detectors, thus reducing costs and errors.
Implementation Method 1
Infrared gas analyzers detect infrared radiation passing through a gas sample. The measurement principle is based on the fact that specific gas components absorb infrared radiation of specific wavelengths.
Implementation Method 2
The absorption in the gas follows Beer's Law which can be written as follows for the light intensity transmitted through an optical path: I=I0×eεLc
Implementation Method 3
The gas flow path from the gas modulation valve to the inlet of the gas sensor is alternately connected to the sample gas inlet and to the reference gas inlet by the gas modulation valve. The switching by the gas modulation valve between the sample gas inlet and the reference gas inlet preferably occurs in a periodical manner at a periodic frequency.
Implementation Method 4
The signal is the difference between light transmitted through the gas and through the reference instead of an absolute value of light intensity. Analyzing the detector signal at the gas modulation frequency strongly suppresses various noise signals with other frequencies.
Data Source
AI summary
Method for wide range gas detection using a gas detection system comprising a sample gas inlet, a reference gas inlet, a gas modulation valve and a gas analyzer, wherein the gas modulation valve alternatingly connects the sample gas inlet to the gas analyzer during a sample gas time period and the reference gas inlet to the gas analyzer during a reference gas time period, characterized in that the sample gas time period is shorter than the reference gas time period such that the sample gas concentration in the gas analyzer is reduced.