Pressure-Based Gas Flow Control with Dynamic Self-Calibration
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Solution Overview
Problem
Current gas flow control systems require complex and expensive controllers and calibration systems, often necessitating recalibration when switching between gases and are prone to errors due to system drift, fouling, and pressure fluctuations, which can lead to costly mistakes in processes like semiconductor manufacturing.
Innovation Solution
A gas flow control method using an upstream valve, a cavity of known volume, and a restrictor element, with control electronics that vary the flow rate oscillatory to maintain an average molecular rate, monitor temperature for density corrections, and calculate flow rates in real-time using pressure variations, reducing the need for recalibration and minimizing component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal sensing methods are used to measure gas mass flow, then flow rate can be monitored, but the system requires frequent recalibration due to sensor drift, fouling, and temperature variations
Solution Approach 1:
The system performs self-calibration by introducing a known test gas flow and automatically adjusting calibration parameters to compensate for drift and fouling, eliminating the need for external recalibration services and maintaining long-term measurement accuracy
Solution Approach 2:
The system uses feedback from pressure differential measurements across the restrictor and flow sensor readings to continuously monitor and adjust calibration factors, automatically compensating for sensor drift and environmental changes without manual intervention
2Measurement precision
If complex calibration systems are implemented to maintain accuracy, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The system automatically performs calibration using built-in test facilities and algorithms, eliminating the need for external calibration equipment and complex manual calibration procedures, thereby maintaining high precision with simpler overall system architecture
Solution Approach 2:
The pressure sensor and control system serve multiple functions including normal flow measurement, calibration reference, and diagnostic monitoring, reducing the need for separate dedicated components and simplifying the overall device structure
3Adaptability or versatility
If traditional flow controllers are used, then gas flow can be controlled, but they require recalibration when switching between different gas types
Solution Approach 1:
The system automatically adjusts calibration parameters based on the specific gas type being used, storing and retrieving gas-specific calibration data to maintain accuracy across different gases without requiring physical recalibration or manual parameter adjustment
Solution Approach 2:
The system automatically detects gas type changes and initiates appropriate calibration routines, eliminating the need for operator intervention and minimizing downtime during gas transitions
4Measurement precision
If pressure-based measurement is used, then flow rate can be calculated, but the system is sensitive to upstream pressure fluctuations and fouling
Solution Approach 1:
The system continuously monitors upstream pressure and uses feedback control to compensate for pressure fluctuations in the flow calculation, while also monitoring for fouling conditions and adjusting measurements accordingly to maintain accuracy despite adverse conditions
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 solution provides continuous, accurate, and cost-effective gas flow control independent of gas type, sensor orientation, fouling, and pressure changes, enabling real-time monitoring and reducing maintenance needs, thus improving process reliability and efficiency.
Implementation Method 1
volumetrically measuring and controlling the average molecular rate of gas flow to the destination
Implementation Method 2
monitor temperature for density corrections
Implementation Method 3
flowing the gas through an upstream valve into a cavity of known volume, then through a restrictor element
Data Source
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AI summary
A method of measuring a molecular rate of gas flow from an upstream source of gas at a pressure higher than a pressure of a destination includes flowing the gas through an upstream valve into a cavity of known volume, then through a restrictor element before proceeding to the destination, controlling the upstream valve to vary a flow rate of the gas through the upstream valve in a determined manner such that its average pressure in the cavity correlates with an average level of gas flow and such that variations in pressure in the cavity induced by varying the flow rate of gas through the upstream valve in the determined manner induce instantaneous pressure variations smaller than 30% of the average pressure in that cavity; and using the variations in the pressure in the cavity associated with varying the flow rate of gas through the upstream valve in the determined manner to determine the molecular rate of gas flow to the destination in real time.