Top Cap Assembly for Capillary Gas Sensors Resisting Condensation
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Solution Overview
Problem
Capillary controlled oxygen sensors face issues with condensation blocking gas flow, particularly in humid environments, and are sensitive to pressure changes, leading to compromised signal output.
Innovation Solution
A top cap assembly with a bulk flow control assembly, including a hydrophobic bulk flow membrane and a moat to collect condensation, and a gas diffuser to ensure continuous gas flow, preventing blockages and maintaining sensor performance under varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If highly restrictive narrow diameter gas capillaries are used to restrict oxygen ingress, then measurement precision is improved, but reliability deteriorates due to easy blockage with condensate
Solution Approach 1:
The gas flow path is segmented into multiple capillaries instead of using a single narrow capillary. This divides the total gas flow requirement across several parallel pathways, reducing the risk that condensation will completely block the gas supply while maintaining the necessary restrictive geometry for precise measurement.
Solution Approach 2:
The invention introduces a vertical dimension to the gas flow system by positioning the capillary inlet above the electrolyte level and using a dip tube arrangement. This dimensional change allows gas to be introduced from above while preventing condensate from blocking the inlet, separating the gas supply function from the liquid electrolyte environment.
2Measurement precision
If long narrow diameter capillaries are used to restrict oxygen ingress, then measurement precision is improved, but device complexity increases due to blockage susceptibility
Solution Approach 1:
The single long capillary is segmented into multiple shorter capillaries arranged in parallel. This segmentation reduces the length of each individual capillary while maintaining the overall restrictive effect, thereby reducing susceptibility to blockage and simplifying the system's reliability without compromising measurement precision.
Solution Approach 2:
The gas introduction system uses a composite structure combining a bulk flow membrane with hydrophobic properties and a porous structure, integrated with the capillary system. This composite approach provides both bulk flow restriction and condensation prevention, reducing device complexity compared to using only long narrow capillaries.
3Reliability
If bulk flow membrane is added to control pressure transient effects, then reliability is improved, but device complexity increases
Solution Approach 1:
The bulk flow membrane is merged with the capillary holder structure, integrating the pressure control function into the existing capillary support geometry. This combination reduces device complexity by eliminating separate components while maintaining the bulk flow control capability for pressure transient resistance.
Solution Approach 2:
The bulk flow membrane serves multiple functions: it provides pressure transient control, supports the capillary structure, and its hydrophobic properties contribute to condensation prevention. This multi-functionality reduces the need for additional components, thereby reducing device complexity while improving reliability.
4Measurement precision
If capillary inlet is positioned at electrolyte level for gas diffusion, then measurement precision is improved, but object-affected harmful factors increase due to condensation blocking
Solution Approach 1:
The capillary inlet is repositioned from the horizontal electrolyte level to a vertical position above the electrolyte. This dimensional change allows gas to diffuse into the electrolyte through the capillary wall along its length while the inlet remains in a condensation-free zone, eliminating the harmful blocking effect while preserving measurement precision.
Solution Approach 2:
The dip tube acts as an intermediary structure that delivers gas from the bulk flow membrane to the capillary inlet positioned above the electrolyte. This intermediary arrangement enables controlled gas introduction while preventing direct contact between the capillary inlet and condensation-prone electrolyte surface.
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 effectively prevents condensation from blocking gas flow and stabilizes sensor output during changes in temperature and humidity, ensuring reliable measurements even in challenging environments like flue gas analyzers.
Implementation Method 1
The bulk flow membrane may comprise a hydrophobic material, preventing condensation from blocking gas flow into the bulk flow membrane
Implementation Method 2
a moat surrounding the raised boss, wherein the moat is operable to collect condensation formed on or around the bulk flow control assembly
Implementation Method 3
the moat is operable to collect condensation formed on or around the bulk flow control assembly
Implementation Method 4
For electrochemical oxygen sensors used to measure concentrations around ambient levels, it may be necessary to greatly restrict the ingress of oxygen into the sensor
Data Source
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AI summary
Embodiments of the disclosure relate to capillary controlled gas sensors comprising a top cap assembly, wherein the top cap assembly is operable to reduce the effects of condensation and pressure changes on the effectiveness of the gas sensor. The top cap assembly comprises a capillary controlled gas flow path, a bulk flow control assembly, and a raised boss surrounded by a moat.