Gas Flow Dilutor Calibration Using Fixed Orifices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gas flow dilutors require expensive and time-consuming annual calibration in laboratories, and existing methods are not suitable for dilutors with fixed flow components like critical orifices, which are faster to stabilize but cannot be adjusted for equal flows.
Innovation Solution
A method and apparatus that use a calibrating fixed flow component and multiple fixed flow components with similar or double flow rates, interconnected and connected to a flow meter, to determine relative flow ratios without measuring actual flows, allowing for frequent in-use calibration using lower-cost, fixed flow components like critical orifices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If annual calibration in laboratories is performed, then calibration accuracy is maintained, but calibration cost and time consumption increase
Solution Approach 1:
The system enables self-calibration by using an internal reference flow component and flow meter to automatically determine relative flow ratios without requiring external laboratory calibration services. The microprocessor controls the calibration sequence and calculates flow ratios using the relationship FD(8B) = FD(8A)×ID(8B)/ID(8A), allowing the dilutor to maintain its own calibration.
Solution Approach 2:
The calibration process is performed preliminarily by establishing flow ratios between components before actual use. The system pre-determines the relative flow characteristics of fixed flow components by comparing their flows against a reference component, storing these ratios for subsequent operational use.
2Speed
If fixed flow components like critical orifices are used, then stabilization speed increases, but flow adjustability decreases
Solution Approach 1:
The system introduces a flow meter as an intermediary measurement device that enables calibration of fixed flow components without requiring them to be adjustable. The flow meter measures the actual flow rates, allowing the system to determine and compensate for variations in fixed flow components' performance through mathematical relationships rather than mechanical adjustment.
Solution Approach 2:
The system changes the calibration approach from direct flow adjustment to ratio-based calibration. By measuring and comparing flow ratios rather than absolute flow values, the system can accurately calibrate fixed flow components that cannot be mechanically adjusted, using the relationship between multiple fixed flow components to establish precise flow proportions.
3Measurement precision
If mass flow controllers are used for calibration, then flow control precision is improved, but device size and cost increase
Solution Approach 1:
The system replaces expensive, complex mass flow controllers with simpler, fixed flow components like critical orifices combined with a flow meter. These fixed flow components are cheaper, more reliable, and require less maintenance. The calibration is achieved through ratio measurements rather than requiring precise absolute flow control, allowing the use of simpler components.
Solution Approach 2:
The invention extracts the essential calibration function from complex mass flow controllers and implements it using simpler components. By separating the measurement function (flow meter) from the control function (fixed flow components), the system achieves calibration capability without requiring large, expensive mass flow controllers.
4Measurement precision
If frequent calibration is performed, then accuracy maintenance is improved, but operational downtime increases
Solution Approach 1:
The self-calibration capability allows frequent calibration without requiring removal from service or external laboratory intervention. The system can perform calibration quickly using its internal reference component and flow meter, maintaining accuracy while minimizing operational disruption.
Data Source
Figure 1
AI summary
The preferred embodiments described herein make possible to use lower cost, fixed flow components, such as critical orifices, which are fast to stabilise to a steady flow. These cannot be adjusted to achieve equal flows but are selected to be sensibly close to their desired flow values. This embodiment determines the true ratios of the flows of all of the flow controlling components. Actual flows are not measured but near equal flows are each fed to a common flow meter and the ratio of the indicated flow meter readings is taken to be the same as the ratio of the flows. Two, near equal flows are then combined and compared to a single flow of approximately the same value, and so on. The flow meter is used only to compare near equal flows so does not need to be calibrated nor linear over a wide range.