Open Path Gas Detector Alignment and Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current open path gas detectors face challenges in accurately detecting low levels of toxic gases due to noise interference, drift in components, and interference fringes, especially when monitoring large areas, and lack a reliable, low-cost solution for gas levels as low as 10 ppm.
Innovation Solution
The design incorporates a transmitter unit with a radiation deflector that includes a non-deflecting part to create a shadow for alignment and a composite signal with multiple modulation frequency components to differentiate gas absorption from harmonic distortion, along with a method to steer the beam for precise alignment and reduce non-linearity errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tuneable diode lasers are used to detect low levels of toxic gases, then the detection capability is improved, but noise interference and interference fringes make it difficult to detect low gas levels
Solution Approach 1:
The laser wavelength is modulated periodically to scan through the absorption band of the target gas. By using periodic modulation and detecting the specific frequency response, the system can distinguish genuine gas absorption signals from random noise and interference fringes, enabling reliable detection at low concentrations of 10 ppm or lower.
Solution Approach 2:
The system uses feedback mechanisms to monitor and adjust the laser wavelength to maintain optimal alignment with the absorption features of the target gas. This feedback control compensates for drift in electronic and optical components over time, ensuring consistent detection precision even in the presence of environmental variations.
2Area of stationary object
If open path gas detectors with path length exceeding 10m are used to monitor large areas, then the monitoring area is improved, but alignment accuracy deteriorates due to drift in components and environmental variations
Solution Approach 1:
The system employs dynamic alignment adjustment mechanisms that can adapt to changes in component positions and environmental conditions. By making the alignment system dynamic rather than static, the detector maintains accurate beam alignment over long paths even when mechanical drift or thermal expansion occurs, enabling reliable operation in large-area monitoring applications.
3Reliability
If reference wavelengths are used to compensate for attenuation, then the reliability is improved, but the device complexity increases due to multiple wavelengths and ratios
Solution Approach 1:
The system uses a single tuneable diode laser that can operate at multiple wavelengths, making the laser source multi-functional. By scanning the laser across different wavelengths including both the target gas absorption wavelength and reference wavelengths, the system achieves reliable compensation for atmospheric attenuation without requiring separate light sources or complex additional components.
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 detection of low gas concentrations by reducing noise and interference, improving alignment accuracy, and providing a reliable measure of gas levels, thereby increasing the reliability and precision of open path gas detection.
Implementation Method 1
The wavelength of the infrared radiation is chosen so that it is absorbed by the gas of interest (hereafter called the 'target gas') but not substantially absorbed by other gases in the atmosphere
Implementation Method 2
a radiation deflector, having a deflecting part and a non-deflecting part, wherein the deflector is configured such that both the deflecting part and the non-deflecting part are located in the path of the radiation emitted by the transmitter
Implementation Method 3
a composite signal with multiple modulation frequency components to differentiate gas absorption from harmonic distortion
Data Source
AI summary
The present invention provides a transmitter unit for an open path gas detector for detecting a target gas and comprises: a radiation transmitter, e.g. a tuneable laser diode, capable of emitting radiation at a wavelength absorbed by the target gas, and a radiation deflector, having a deflecting part and a non-deflecting part, e.g. a mirror having a non-reflective part. The deflecting part and the non-deflecting part are located in the path of the radiation emitted by the transmitter and the non-deflecting part does not deflect the said radiation emitted by the transmitter or does so to a different extent than the deflecting part. In this way, the beam has a core in shadow that can be used to align the beam with a receiver unit. The radiation deflector is preferably a mirror having a reflective surface for reflecting radiation emitted by the transmitter and a non-reflective part that does not reflect the said radiation emitted by the transmitter or does so to a lesser extent that the reflecting surface. The non-reflective part is preferably transparent so that it allows radiation to pass through it, which can be used to measure the wavelength of the transmitter and, if necessary correct it.