Phase Shift Time-of-Flight Detection for Ultrasonic Flow Meters
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Solution Overview
Problem
Ultrasonic flow meters using the time-of-flight method face challenges in achieving robust and stable measurements due to external influences such as temperature, fluid properties, and measurement setup variations, leading to instability and high power consumption in battery-powered devices.
Innovation Solution
The method introduces a phase shift in the transmitted signal train, allowing for the detection of a stable reference marker in the time domain, which helps in accurately assigning wave periods and determining time-of-flight signals, thereby improving measurement stability and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If amplitude-based methods (first hit level) are used to detect time-of-flight, then the measurement process is simple, but the measurement stability deteriorates due to changes in wave train amplitude caused by temperature, flow speed, and aging
Solution Approach 1:
The patent changes the detection parameter from amplitude-based (first hit level) to time-based (phase shift). By introducing a predetermined phase shift between first and second groups of waves and detecting the time position of this phase shift, the method achieves stable reference points that are independent of amplitude variations caused by temperature, flow speed, and aging effects.
2Reliability
If correlation method is used to detect time-of-flight, then measurement stability is improved, but power consumption increases which is problematic for battery-powered devices
Solution Approach 1:
The patent extracts only the essential time position information of the phase shift from the received signal, rather than performing the complete correlation calculation. By detecting when the phase shift occurs in time and using this as a reference, the system achieves stable measurements with significantly reduced computational effort and power consumption compared to full correlation methods.
3Reliability
If time delay trigger is used to mask undesired zero crossings, then measurement stability is improved, but device complexity increases due to complex calculations needed to track wave trains
Solution Approach 1:
The patent applies preliminary action by introducing a known phase shift between the first and second groups of waves before transmission. This predetermined phase shift serves as a built-in reference marker that simplifies the detection process, eliminating the need for complex real-time tracking calculations required by time delay trigger methods.
Data Source
AI summary
In an embodiment a method includes transmitting a signal train through a medium, wherein the signal train includes a sequence of waves of a first group and of a second group, the first and second groups being shifted in a time domain according to a predetermined phase shift, receiving the signal train as a received signal train and as a function of time, detecting a phase shift in the received signal train, assigning wave periods of the received signal train to respective wave periods of the first group using the detected phase shift as reference and determining a sequence of time-of-flight signals from the sequence of waves of the first group and the assigned wave periods of the received signal train, respectively.