Mass Flow Controller Adaptive CF Value Selection
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Solution Overview
Problem
Conventional mass flow controllers use a single conversion factor (CF value) for all flow rate set values, leading to errors in flow rate conversion due to varying CF values for different concentrations and flow rates, and separate calibration for each gas type is cumbersome and costly.
Innovation Solution
A mass flow controller system with a relation data store, reference gas flow rate conversion, sample gas flow rate calculation, and CF value update part that selects the optimal CF value for each flow rate value, updating the CF value based on differences between the target and actual flow rates to maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single CF value is used for all flow rate set values, then the device complexity is reduced, but the measurement precision deteriorates due to errors in flow rate conversion
Solution Approach 1:
The patent divides the single CF value into multiple CF values corresponding to different flow rate ranges. The measurement range is segmented into multiple sections, and different CF values are applied to different sections based on the target flow rate set value, thereby improving conversion accuracy without overwhelming complexity
Solution Approach 2:
The patent implements dynamic selection of CF values based on the target flow rate set value. The system automatically switches between different CF values according to the current operating point, making the conversion factor adaptive rather than static, which resolves the contradiction between simplicity and precision
2Measurement precision
If separate calibration is conducted for each gas type, then the measurement precision is improved, but the ease of operation deteriorates due to troublesome calibration procedures
Solution Approach 1:
The patent creates a universal calibration method using reference gas that can be applied to multiple different sample gas types. Instead of requiring separate calibration procedures for each gas type, the system uses a single reference gas calibration that establishes baseline CF values, which are then adjusted dynamically based on the specific gas type and flow rate conditions
Solution Approach 2:
The system performs automatic CF value selection and adjustment based on the target flow rate set value without requiring manual intervention for each gas type calibration. The control device automatically determines the appropriate CF value and applies it, making the calibration process self-service rather than manually intensive
3Measurement precision
If multiple CF values are stored for different flow rate ranges, then the measurement precision is improved, but the device complexity increases due to additional data management
Solution Approach 1:
The patent pre-calculates and stores multiple CF values corresponding to different flow rate ranges before actual operation. This preliminary preparation allows the system to quickly select the appropriate CF value during operation without complex real-time calculations, reducing operational complexity while maintaining high precision
Solution Approach 2:
The patent replaces complex mechanical or manual CF value selection mechanisms with an automated control device that electronically stores and selects CF values based on the target flow rate set value. This substitution of electronic control for manual or mechanical systems simplifies data management while improving precision
Data Source
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AI summary
This invention is to make it possible to control a flow rate output by a mass flow controller with high accuracy, and a relation data that indicates a corresponding relation between a flow rate of a reference gas and a CF value of a sample gas is stored, a target flow rate is converted into a reference gas flow rate by the use of a predetermined CF value, a sample gas flow rate is calculated from the converted reference gas flow rate and a CF value corresponding to the reference gas flow rate, the sample gas flow rate is compared with the target flow rate, and the CF value that is used for conversion of the reference gas flow rate or calculation of the sample gas flow rate is updated by the use of the corresponding relation based on the error between the sample gas flow rate and the target flow rate.