Multi-Reflection Gas Sensor with Humidity Compensation
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Solution Overview
Problem
Existing gas measurement systems face challenges in accurately detecting low concentrations of target gases in industrial environments due to interference from environmental influences such as humidity, salt content, and condensation, especially in explosion-proof designs, which complicates the measurement of gases like methane and propane.
Innovation Solution
A device with a multi-reflection measuring cell using specific infrared wavelengths and reference wavelengths to compensate for humidity and salt influences, combined with heating elements to control temperature and reduce condensation, allowing for precise detection of target gases like methane and propane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heating elements are used to reduce condensation in humid environments, then measurement reliability is improved, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the heating power based on humidity sensor feedback. The control unit monitors humidity levels and modulates the heating elements accordingly, increasing power when condensation risk is high and reducing power when conditions are favorable, thereby maintaining measurement reliability while optimizing energy consumption
Solution Approach 2:
The patent implements feedback control through humidity sensors that continuously monitor the internal cuvette environment and feed this information to the control unit. This closed-loop system enables real-time adjustment of heating elements to prevent condensation formation, ensuring measurement reliability while avoiding excessive energy consumption by heating only when necessary
2Measurement precision
If reference wavelengths are used to compensate for humidity and salt influences, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses reference wavelengths as intermediary measurement channels that detect environmental influences (humidity and salt content) without being absorbed by the target gas. These reference channels act as mediators that allow the system to separate and compensate for environmental effects from actual gas concentration signals, improving measurement precision through mathematical correction
Solution Approach 2:
The patent segments the measurement process into multiple independent wavelength channels: target gas measurement wavelengths and reference wavelengths for environmental monitoring. This segmentation allows parallel measurement of different parameters (gas concentration and environmental conditions) that can be independently processed and combined through evaluation algorithms to achieve high precision
3Measurement precision
If multi-reflection measuring cell is used to increase optical path length, then detection sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent employs curved or reflective surfaces within the measuring cell to create multiple reflections of the light beam. This curvature-based design extends the optical path length significantly within a compact volume, enhancing detection sensitivity for low gas concentrations while maintaining a space-efficient and relatively simple device structure
Solution Approach 2:
The patent transforms the optical path from a simple linear dimension to a multi-dimensional path through multiple reflections between curved surfaces. This dimensional transformation allows the light to traverse a much longer effective path length within a compact physical volume, improving sensitivity without proportionally increasing device size or complexity
4Reliability
If explosion-proof design is implemented to ensure safety, then safety is improved, but measurement reliability deteriorates due to condensation and humidity
Solution Approach 1:
The patent changes the temperature parameter within the explosion-proof cuvette by employing controlled heating elements. This temperature elevation prevents condensation formation on the cuvette walls and optical components, eliminating the harmful effects of humidity and condensation that would otherwise degrade measurement reliability while maintaining explosion-proof safety containment
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
The device effectively compensates for environmental influences, enabling accurate detection of target gas concentrations with high sensitivity and reliability, even in humid and salty environments, while maintaining explosion-proof safety standards.
Implementation Method 1
Absorption of light by the gas being measured leads to a reduced detector signal, which is evaluated as the measured quantity
Implementation Method 2
the inner wall of these multireflection cells is completely reflective, so that when using a radiation source with an undirected light beam, a portion of the emitted light reaches the detector via a longer path due to multiple reflections at the wall
Implementation Method 3
heating the optics is a known and effective method... Heating can only prevent the formation of condensate and water droplets on the walls of the cuvette and the optical components
Implementation Method 4
an optical bandpass filter element is arranged in front of the measuring detector, which is configured to transmit light of a measurement wavelength in the infrared range
Implementation Method 5
the first and second reference wavelengths and the respective associated bandwidth and the maximum value of the transmission for the first and the second reference wavelength are selected such that there is no signal attenuation due to the target gas or any other gas from the measurement environment, and environmental influences, namely the direct influence of humidity and the indirect influence of humidity due to salinity, summarily result in the same signal attenuation as the signal attenuation at the measurement wavelength
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
Device for optical detection of a target gas in gas mixtures, with an operation and evaluation unit (8) and a measurement cuvette (3), which is configured as a multi-reflection measurement cuvette with optically reflective surfaces on its interior walls and which has a gas inlet (5) constructed to exchange gases and gas mixtures with a measurement environment (6); a radiation source (4) for emitting light into the measurement cuvette, a measuring detector (21) and a reference detector unit (23, 25, 27) being provided on the measurement cuvette (3), the measuring detector (21) and the reference detector unit (24) being constructed to detect the light of the radiation source (4) and convert same into electrical signals corresponding to the intensity of the detected light, an optical bandpass filter element (22) constructed to transmit light of a measurement wavelength being arranged upstream of the measuring detector (21), and an optical double-bandpass filter unit (24, 26, 28) constructed to transmit light of a first reference wavelength (31) and light of a second reference wavelength (32) being arranged upstream of the reference detector unit (23, 25, 27), the operation and evaluation unit (8) being constructed to operate the radiation source (4) and to acquire the electrical signals of the measurement detector (21) and the reference detector unit (23, 25, 27).