Remote Pressure Sensing Flow Node for Accurate Process Gas Delivery
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Solution Overview
Problem
Conventional mass flow controllers (MFCs) face inefficiencies in accuracy, space consumption, and cost due to the need for local pressure measurement, which also results in slow bleed down times when adjusting gas flow rates.
Innovation Solution
A flow node utilizing a remote pressure measurement device with a characterized restrictor and valve seat configuration, minimizing the volume between them, allows for accurate gas delivery without local pressure measurement, reducing space and cost while improving dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a local pressure transducer is used within the MFC to measure process gas pressure, then measurement accuracy is improved, but device volume and cost increase
Solution Approach 1:
The pressure transducer is extracted from the MFC device and relocated to a remote position upstream of the restrictor. The MFC now uses only a temperature sensor for local measurements, while pressure measurement is performed remotely by the extracted transducer, reducing the MFC volume while maintaining measurement capability.
Solution Approach 2:
A characterized restrictor is introduced as an intermediary element between the remote pressure transducer and the MFC. This restrictor creates a known pressure drop relationship that allows the remote pressure measurement to accurately represent the pressure at the MFC inlet, enabling accurate flow measurement without local pressure sensing.
2Measurement precision
If a local pressure transducer is used within the MFC, then pressure measurement accuracy is improved, but device cost increases
Solution Approach 1:
The pressure transducer is extracted from the MFC device and relocated upstream. This allows the MFC to be manufactured without integrating a pressure transducer, reducing component costs and simplifying the manufacturing process while maintaining pressure measurement functionality through the remote sensor.
Solution Approach 2:
The remote pressure transducer serves multiple functions: it measures pressure for flow calculation, provides feedback for control algorithms, and enables the MFC to achieve specified accuracy without requiring expensive local pressure sensing components within the MFC assembly.
3Stability of the object's composition
If a larger volume V1 is used for pressure measurement, then pressure measurement stability is improved, but bleed down time increases
Solution Approach 1:
The pressure measurement function is extracted from the MFC volume V1 and performed remotely upstream. This eliminates the need for a large local measurement volume within the MFC, allowing the MFC to achieve fast bleed down times while the remote pressure transducer maintains stable pressure measurements through its own positioning and characterization.
Solution Approach 2:
The mechanical pressure measurement system within the MFC is replaced with a remote electronic pressure sensing system. The characterized restrictor creates a predictable pressure relationship that allows electronic calculation of MFC inlet pressure from remote measurements, eliminating the need for large mechanical measurement volumes and enabling faster response times.
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 enables efficient, accurate, and cost-effective gas delivery with reduced space requirements and faster bleed down times compared to conventional MFCs, achieving a wider dynamic range of flow rates.
Implementation Method 1
a characterized restrictor is placed in series and adjacent with the valve seat to provide a primary flow restriction
Data Source
AI summary
A flow node includes characterized restrictor in series and adjacent with a valve to provide a primary flow restriction with a minimized volume between the two. A conductance of the characterized restrictor is low enough relative to the valve seat to cause a pressure drop that is sufficiently large relative to the pressure drop across the valve seat that a pressure measurement device is located upstream of the valve is used to determine the pressure to the inlet of the restrictor. A vent can be included to reduce bleed time. Multiple flow nodes in parallel increase a dynamic range.