Flow Controller Calibration for Gas Chromatograph Pressure Errors
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Solution Overview
Problem
The existing gas chromatograph apparatus' method for measuring total flow volume of carrier gas is inaccurate due to differences in supply pressure and laminar flow tube resistance, leading to errors in quantitative analysis.
Innovation Solution
A flow controller that stores two calibration curves for different set supply pressures, allowing for accurate calculation of total flow volume based on detected pressure differences, and includes an atmospheric pressure correction mechanism to minimize the influence of atmospheric pressure changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single calibration curve is used for flow measurement, then the device complexity is reduced, but the measurement precision deteriorates when supply pressure varies from the calibration pressure
Solution Approach 1:
The system dynamically selects or interpolates between multiple calibration curves based on the actual supply pressure detected. This dynamic adaptation allows the measurement system to maintain high precision across varying pressure conditions without requiring a single complex universal calibration curve, thus resolving the contradiction between device simplicity and measurement accuracy.
Solution Approach 2:
The patent changes the calibration parameter (supply pressure) by storing multiple calibration curves at different reference pressures. When the actual supply pressure differs from the calibration pressure, the system selects or interpolates the appropriate calibration curve, thereby maintaining measurement precision across different operating conditions without significantly increasing device complexity.
2Adaptability or versatility
If the supply pressure varies from the calibration pressure, then the adaptability to different operating conditions is improved, but the measurement precision deteriorates due to pressure difference errors
Solution Approach 1:
The system performs preliminary calibration at multiple different supply pressures and stores the resulting calibration curves in advance. When actual measurement is performed, the system selects or interpolates the appropriate pre-prepared calibration curve based on the detected supply pressure, thereby maintaining high measurement precision across a wide range of operating conditions without real-time calibration complexity.
3Ease of operation
If atmospheric pressure changes are not corrected, then the ease of operation is maintained, but the measurement precision deteriorates due to atmospheric pressure influence
Solution Approach 1:
The system incorporates atmospheric pressure detection and uses this feedback information to correct the flow measurement. By continuously monitoring atmospheric pressure and applying corrections based on the detected variations, the system maintains high measurement precision automatically without requiring manual intervention, thus resolving the contradiction between ease of operation and measurement precision.
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 flow controller ensures accurate measurement of total flow volume by using the appropriate calibration curve based on the detected supply pressure, reducing errors and improving the reliability of quantitative analysis in gas chromatograph apparatus.
Implementation Method 1
a laminar flow tube (flow channel resistance) 21 configured to cause an adequate pressure drop in the carrier gas
Implementation Method 2
a pressure difference sensor (pressure difference detecting portion) 23 configured to detect a pressure difference Δp between a supply pressure pin on an upstream side of the laminar flow tube 21 and a pressure on a downstream side thereof
Data Source
AI summary
A flow controller including a flow channel resistance disposed in a carrier gas supply flow channel, a control valve, pressure detecting portion 22 and a pressure difference detecting portion, a storage part storing a first calibration curve indicating a correlation between a pressure difference Δp and a total flow volume ftemp1 at the first set supply pressure Pin, ref1 and a second calibration curve indicating a correlation between a pressure difference Δp and the total flow volume ftemp2 at a second set supply pressure Pin,ref2 larger than the first set supply pressure Pin,ref1 is provided. A total flow volume f of the carrier gas is calculated based on the supply pressure pin detected by the pressure detecting portion, pressure difference Δp information detected by the pressure difference detecting portion, the first calibration curve and the second calibration curve.