Flow Measuring Device Mode Switching for Low Flow Accuracy
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Solution Overview
Problem
Flow measuring devices, particularly ultrasonic meters, experience significant measurement errors at low flow rates due to noise components, leading to inaccurate volume flow rate determinations and acceptance issues, especially during start-up phases or when flow rates are transient and near the threshold.
Innovation Solution
The flow measuring device switches between operating modes based on predefined flow rate parameters, storing current and previous parameters in a data memory to account for slow changes and transient flow directions, thereby avoiding the discard of measurement data and enhancing accuracy by considering a fixed number of previous flow rate parameters when switching modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If very low measured volume flow rates are discarded to counteract noise components, then measurement errors at low flow rates are reduced, but measurement errors during start-up phase and transient flow conditions increase
Solution Approach 1:
The invention introduces a start-up phase with a predefined number of measurement cycles before normal measurement begins. During this preliminary phase, volume flow rates are determined and stored, and a switchover to normal measurement is triggered when the flow rate exceeds a threshold for a specified number of consecutive cycles. This preliminary action ensures that transient conditions are properly handled while maintaining accuracy during stable operation.
Solution Approach 2:
The invention dynamically adjusts the measurement behavior based on the operational phase. During the start-up phase, the system uses different evaluation criteria (storing multiple measurements, requiring threshold exceedance for N consecutive cycles) compared to normal operation. This dynamic adaptation allows the system to optimize for reliability during transient conditions while maintaining precision during steady-state operation.
2Measurement precision
If a three-phase measurement approach is used with thresholds for extended zero range and start-up phase, then measurement errors at very low flow rates are reduced, but measurement errors occur when flow rates frequently occur near the start-up threshold
Solution Approach 1:
The invention requires that the flow rate threshold be exceeded for a predefined number of consecutive measurement cycles before switching to normal measurement mode. This preliminary requirement ensures that transient fluctuations near the threshold do not trigger premature mode switching, while still allowing timely transition when sustained flow conditions occur.
Solution Approach 2:
The system continuously monitors the volume flow rate during the start-up phase and uses feedback from multiple consecutive measurements to determine whether to switch to normal measurement. This feedback mechanism involving N consecutive threshold exceedances provides stable control that prevents oscillation between measurement modes while maintaining sensitivity to sustained flow conditions.
3Measurement precision
If flow rate parameters are discarded during extended zero range, then noise-induced false measurements are eliminated, but previous flow rate parameters cannot be used to improve accuracy during mode transitions
Solution Approach 1:
The invention stores volume flow rates determined during the start-up phase in a buffer, preserving this information for potential use. When the switchover condition is met, the system can utilize the stored flow rate information to initialize normal measurement, thereby preventing complete loss of data from the transition phase while maintaining noise rejection during extended zero range.
Solution Approach 2:
The system temporarily discards flow rate parameters during extended zero range conditions to eliminate noise effects, but recovers and utilizes the stored flow rate information when transitioning to normal measurement mode. This selective discarding and recovery strategy maintains measurement precision during noisy conditions while preserving valuable information for accurate mode transitions.
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 significantly improves measuring accuracy by accounting for previous flow rate parameters during mode transitions, reducing errors associated with low flow rates and transient changes, and maintaining robust start-up behavior without an extended zero range, thus providing more reliable volume quantity measurements.
Implementation Method 1
A flow velocity can be determined by comparing the times of flight of an ultrasonic wave between the ultrasonic transducers for both measuring directions
Implementation Method 2
ultrasonic-based flow measuring devices, which typically use two ultrasonic transducers attached to the measurement volume
Data Source
AI summary
A flow measuring device detecting a fluid volume quantity since a start of a measurement includes a processing device determining a current flow rate parameter at measurement times using measurement data of a sensor, to increase a volume quantity based on a current flow rate parameter when operating in a first operating mode, and to keep the volume quantity constant when operating in a second mode. The processing device stores the current flow rate parameter for each measurement time in a data memory, resulting after several measuring times in storing previous flow rate parameters determined at these measuring times. Upon satisfying a switchover condition, depending on the current flow rate parameter, during operation in the second mode, the processing unit switches over to the first mode, and the volume quantity increases as a function of the current flow rate parameter and a predefined number of previous flow rate parameters.