Differential Pressure Flow Control for Sensor Drift Accuracy
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Solution Overview
Problem
Flow rate control devices in semiconductor and chemical manufacturing face accuracy issues due to zero-point drift in pressure sensors, particularly when downstream pressure is high, leading to significant measurement errors.
Innovation Solution
A flow rate control device incorporating a control valve, an upstream pressure sensor, a differential pressure sensor, and an arithmetic control circuit that performs proportional or differential pressure control based on the outputs from these sensors to minimize the impact of zero-point drift, using a differential pressure sensor with a strain sensor to directly measure pressure differences and an integrated sensor configuration for compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pressure sensor is used to measure upstream pressure for flow rate control, then flow rate control can be performed under critical expansion condition, but measurement accuracy deteriorates due to zero-point drift especially at high downstream pressures
Solution Approach 1:
The patent combines the upstream pressure sensor and downstream pressure sensor into an integrated differential pressure sensor assembly. This merging allows simultaneous measurement of both pressures with a single sensor unit, enabling accurate differential pressure calculation while reducing the impact of zero-point drift through differential measurement methodology.
Solution Approach 2:
The patent introduces a differential pressure sensor as an intermediary measurement device that directly measures the pressure difference between upstream and downstream sides. This intermediary approach avoids the need to rely solely on upstream pressure measurements, thereby mitigating the effect of zero-point drift on flow rate control accuracy.
2Device complexity
If only an upstream pressure sensor is used, then the device complexity is reduced, but the flow rate control accuracy deteriorates under non-critical expansion condition
Solution Approach 1:
The patent merges multiple pressure sensing functions into a single integrated sensor assembly that can measure both upstream pressure and downstream pressure (or differential pressure directly). This combination maintains relatively simple device structure while enabling accurate flow rate determination under both critical and non-critical expansion conditions.
Solution Approach 2:
The integrated pressure sensor assembly performs multiple functions: measuring upstream pressure for critical expansion control, measuring downstream pressure for non-critical expansion control, and calculating differential pressure for enhanced accuracy. This multi-functionality allows the same sensor system to handle various operating conditions without increasing device complexity.
3Measurement precision
If separate upstream and downstream pressure sensors are used, then flow rate control accuracy is improved under non-critical expansion condition, but device complexity and calibration difficulty increase
Solution Approach 1:
The patent combines separate upstream and downstream pressure sensors into a single integrated differential pressure sensor assembly. This merging reduces the number of independent sensor components, simplifies the overall device structure, and reduces calibration complexity while maintaining the capability to perform accurate differential pressure measurements for flow rate control.
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 provides a flow rate control device with reduced error from pressure sensor drift, especially at high downstream pressures, enabling accurate control over a wide flow rate range with improved responsiveness and reduced calibration challenges.
Implementation Method 1
a differential pressure sensor for measuring the differential pressure between the upstream side and the downstream side of the restriction part
Data Source
AI summary
The flow rate control device 10 includes a control valve 11, a restriction part 12 provided downstream of the control valve 11, an upstream pressure sensor 13 for measuring a pressure P1 between the control valve 11 and the restriction part 12, a differential pressure sensor 20 for measuring a differential pressure ΔP between the upstream and the downstream of the restriction part 12, and an arithmetic control circuit 16 connected to the control valve 11, the upstream pressure sensor 13, and the differential pressure sensor 20.