Optical Gas Sensor Thermal Isolation via Light Guide
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Solution Overview
Problem
High temperature environments in chemical processes, such as CVD, significantly shorten the lifetime of NDIR gas concentration sensors and lead to performance degradation due to contamination of gas sample cell walls, necessitating a new optical gas concentration measurement apparatus that can operate effectively in such conditions.
Innovation Solution
An optical gas concentration measurement apparatus with a thermally insulated enclosure and thermally-insulating light-guiding elements that isolate temperature-sensitive components and reduce the impact of gas sample cell wall contamination by directing light away from the walls, using reflective elements to maintain optical access and enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NDIR gas concentration sensors are used in high temperature environments, then gas concentration monitoring is achieved, but the lifetime of electronic components is dramatically shortened
Solution Approach 1:
The system is divided into a high-temperature zone (gas sample cell in process chamber) and a low-temperature zone (electronic components in enclosure). The light source and detector are positioned outside the process chamber, separated from high-temperature gases by a port interface, thereby protecting temperature-sensitive components while maintaining measurement capability.
Solution Approach 2:
A port interface structure acts as an intermediary between the high-temperature process chamber and the low-temperature electronic components. This interface includes thermal barriers and light transmission pathways that allow optical signals to pass while blocking thermal energy, protecting the light source and detector from direct thermal exposure.
2Reliability
If reflective walls are used in gas sample cell to aid light propagation, then light transmission is enhanced, but reflectance is lost over time due to contamination
Solution Approach 1:
The reflective walls are extracted from the gas sample cell environment and replaced with a port interface structure that provides light transmission without requiring reflective surfaces in contact with process gases. The light path is configured to transmit through the port interface without relying on reflective walls that would be contaminated by the gas environment.
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 solution extends the lifetime of the measurement apparatus by limiting thermal exposure and maintaining precise temperature control, while reducing the impact of contamination on light transmission, resulting in superior long-term performance and accurate gas concentration measurements.
Implementation Method 1
a first thermally-insulating, light-guiding element passing through a first access port of the thermally insulated enclosure, the first thermally-insulating, light-guiding element configured to direct light from the light source to the gas sample cell
Implementation Method 2
a thermally insulated enclosure having one or more access ports and a gas sample cell situated within the thermally insulated enclosure
Implementation Method 3
the gas sample cell comprising one or more optical windows and one or more gas flow ports
Data Source
AI summary
An optical gas concentration measurement apparatus is disclosed. The optical gas concentration measurement apparatus includes a thermally insulated enclosure that has a gas sample cell situated within. A thermally-insulating, light-guiding element passes through an access port of the thermally insulated enclosure and is configured to direct light from a light source outside of the thermally insulated enclosure to the gas sample cell. A light detector outside of the thermally insulated enclosure is optically coupled to the gas sample cell and an electronic assembly outside of the thermally insulated enclosure is configured to receive information from the light detector.