Flow Meter Self-Calibration Using Pulse Frequency Thresholds
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Solution Overview
Problem
Existing methods for measuring liquid flow through conduits require factory-based calibration for each flow meter due to significant variation in measurement error across the same type of meters, necessitating experimental determination of calibration curves for each individual unit, which is inefficient and impractical.
Innovation Solution
A method that determines the volume of liquid flowing through a conduit by processing signals from a rotor-driven flow meter, using a pre-determined value based on the conditions of use rather than the flow meter's characteristics, allowing for accurate measurement of small volume flows without increasing resistance and eliminating the need for individual calibration, suitable for various types of flow meters including jet impeller meters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory-based calibration is performed for each flow meter to achieve accurate measurement, then measurement precision is improved, but device complexity and manufacturing time increase
Solution Approach 1:
The flow meter system performs self-calibration by automatically determining calibration parameters during operation. The microcontroller counts pulses from the rotor and measures time intervals, then calculates the calibration factor K by comparing measured flow rates with expected values, eliminating the need for external factory calibration services
Solution Approach 2:
The system dynamically adjusts the calibration parameter K based on operating conditions. By changing the calibration factor from a fixed factory-set value to a dynamically determined value based on actual pulse counting and time measurement, the system adapts to variations between individual meters without requiring manual calibration
2Measurement precision
If individual calibration curves are determined experimentally for each flow meter, then measurement precision is improved, but productivity decreases
Solution Approach 1:
Each flow meter independently determines its own calibration parameters during normal operation without requiring external calibration equipment or procedures. The microcontroller automatically performs pulse counting and time measurement to calculate the calibration factor, eliminating the need for separate calibration processes for each unit
Solution Approach 2:
The system performs calibration actions automatically during routine operation rather than requiring separate preliminary calibration steps. The calibration factor is determined as part of the normal measurement process, integrating calibration into the operational workflow and eliminating dedicated calibration time
3Measurement precision
If flow meter characteristics are used for calibration, then measurement accuracy is improved, but adaptability decreases
Solution Approach 1:
The calibration method is designed to be universal across different flow meter types and operating conditions. The microcontroller-based pulse counting and time measurement approach works with various rotor designs and flow rates, allowing a single calibration procedure to serve multiple meter types without modification
Solution Approach 2:
The calibration factor K is not fixed but dynamically determined based on actual operating conditions. The system continuously monitors pulse frequency and time intervals, adjusting the calibration parameter in real-time to adapt to varying flow rates and operational states, making the calibration process versatile across different operating scenarios
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
This approach enables accurate measurement of liquid volumes with reduced calibration variability between flow meters of the same type, improving efficiency and accuracy, especially at low flow rates, and reduces the need for factory-based calibration, making it suitable for applications like beverage dispensing systems.
Implementation Method 1
a flow meter including a rotor drivable by liquid passing through the flow meter
Implementation Method 2
at least one sensor for detecting passage of at least one of the at least one signalling devices and generating a signal representative of a pulse sequence
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
A method of determining a volume of liquid flowing through a conduit (9,10,15) includes receiving a signal from a flow meter (16) including a rotor (22) drivable by liquid flowing through the flow meter (16). The signal is representative of pulses obtainable by detecting passage of at least one signalling device (26) of which movement is at least synchronised with that of the rotor (22). A number (N) of the pulses within a time interval (Δt) is determined. A measure (f) of a pulse frequency within the time interval (Δt) is determined. The volume is determined as a function of a number (N) of pulses within the time interval (Δt) if the measure (f) is indicative of a pulse frequency above a certain value (y). The volume is determined as a pre-determined value (z) upon determining that the measure (f) is indicative of a pulse frequency equal to or lower than the certain value (y).