Thermal Flowmeter Automatic Gas Calibration
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Solution Overview
Problem
Conventional thermal flowmeters require manual setting changes and extensive calibration for different gas types, leading to inaccuracies in flow rate measurement, as they cannot automatically distinguish or adjust for varying fluid types and thermal conductivities.
Innovation Solution
A thermal flowmeter that calculates a fluid-specific value based on upstream and downstream voltage parameters, allowing automatic adjustment of flow rate calibration and conversion factors according to thermal conductivity, enabling accurate flow rate measurement across different gas types without pre-calibration for each type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual setting changes and extensive calibration are performed for different gas types, then flow rate measurement accuracy is improved, but user intervention time and calibration time increase significantly
Solution Approach 1:
The thermal flowmeter automatically detects gas type by measuring thermal conductivity through the electrical resistive elements and self-adjusts the conversion factor without requiring manual calibration. The system performs self-service by autonomously adapting to different gas types based on real-time thermal conductivity measurements, eliminating the need for users to perform time-consuming manual calibration procedures for each gas type.
Solution Approach 2:
The system dynamically changes the conversion factor parameter based on measured thermal conductivity values. By detecting changes in thermal conductivity of different gas types and automatically adjusting the corresponding conversion factor, the system adapts measurement parameters in real-time to maintain accuracy across various gas types without manual intervention.
2Measurement precision
If manual setting changes are made for different gas types, then flow rate measurement accuracy is improved, but ease of operation deteriorates due to complicated setting changes
Solution Approach 1:
The thermal flowmeter automatically detects gas type by measuring thermal conductivity through the electrical resistive elements and self-adjusts the conversion factor without requiring manual calibration. The system performs self-service by autonomously adapting to different gas types based on real-time thermal conductivity measurements, eliminating the need for users to perform time-consuming manual calibration procedures for each gas type.
Solution Approach 2:
The system replaces manual mechanical adjustment of settings with an automated detection and adjustment mechanism. By using electrical resistive elements to sense thermal conductivity and automatically computing the appropriate conversion factor, the system substitutes manual operation with an automated sensing and calculation process, significantly improving ease of operation.
3Ease of manufacture
If flow rate calibration curve data is calibrated using inert gas, then calibration process is simplified, but measurement accuracy deteriorates when measuring corrosive or reactive gases without correction
Solution Approach 1:
The system dynamically changes the conversion factor parameter based on measured thermal conductivity values. By detecting changes in thermal conductivity of different gas types and automatically adjusting the corresponding conversion factor, the system adapts measurement parameters in real-time to maintain accuracy across various gas types without manual intervention.
Solution Approach 2:
The system uses thermal conductivity as an intermediary parameter to bridge the gap between inert gas calibration and corrosive/reactive gas measurement. By measuring thermal conductivity of the actual gas and using it to adjust the conversion factor, the system creates an intermediate adaptation layer that maintains calibration simplicity while achieving accuracy for different gas types.
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
Enables high accuracy flow rate measurement and automatic setting adjustments for varying fluid types, reducing user intervention and calibration time, and allowing for precise flow rate control in semiconductor manufacturing processes.
Implementation Method 1
two electrical resistive elements that are provided on the upstream and downstream sides on the outer surface of the narrow tube... applied voltages are controlled so as to make the temperatures of the upstream and downstream side electrical resistive elements constant
Data Source
AI summary
The present invention is configured to, on the basis of an upstream side parameter having a value that is related to a change rate of an upstream side voltage when a flow rate of measuring target fluid changes, and a downstream side parameter having a value that is related to a change rate of a downstream side voltage when the flow rate of the measuring target fluid changes, calculate a fluid-specific value exhibiting a specific value depending on the thermal conductivity of the fluid.