Ultrasonic Flow Meter Trigger and Zero-Cross Detection
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Solution Overview
Problem
Existing ultrasonic flow velocity measurement methods face challenges in accurately detecting the zero cross point of peak waveforms with high signal-to-noise ratio, as the peak waveform for trigger detection does not necessarily coincide with the waveform having a high S/N ratio, leading to inaccuracies in propagation time difference measurement.
Innovation Solution
The measurement apparatus employs a method where the trigger detecting section identifies a peak waveform with a large amplitude difference between consecutive peak waveforms to set the trigger level, and the specifying section detects the zero cross point from a peak waveform with a high S/N ratio, separate from the trigger-determined waveform, to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the trigger level is set based on the peak waveform with the largest amplitude, then the trigger detection is simplified, but the zero cross point detection accuracy deteriorates because the peak waveform with largest amplitude does not necessarily have the highest S/N ratio
Solution Approach 1:
The patent segments the waveform analysis into two independent parts: trigger detection based on peak amplitude and zero cross point detection based on S/N ratio. The trigger level is determined from the peak waveform with largest amplitude, while the zero cross point is detected from the peak waveform with highest S/N ratio, allowing each function to optimize for its specific requirement without interference
Solution Approach 2:
Different quality criteria are applied to different detection purposes: peak amplitude is used for trigger detection simplicity, while S/N ratio is used for zero cross point accuracy. This local quality differentiation allows each detection process to use the most appropriate criterion for its specific function
2Device complexity
If the zero cross point is detected from the peak waveform determined by trigger level, then the detection process is streamlined, but measurement accuracy deteriorates due to noise interference in peak waveforms with low S/N ratio
Solution Approach 1:
The detection process is segmented into trigger detection (based on peak amplitude) and zero cross point detection (based on S/N ratio). This segmentation allows the system to use different optimization criteria for each detection stage, improving overall measurement accuracy without significantly increasing complexity
Solution Approach 2:
The patent changes the selection parameter from peak amplitude (for trigger) to S/N ratio (for zero cross point). By evaluating peak waveforms based on S/N ratio rather than just amplitude, the system identifies the most reliable waveform for accurate zero cross point detection, thereby improving measurement precision
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 allows for precise detection of the zero cross point, improving the accuracy of flow velocity calculation by distinguishing between waveforms based on amplitude differences and S/N ratios, thereby enhancing the reliability of propagation time period measurements.
Implementation Method 1
By measuring a time period in which an ultrasonic wave is propagated in a medium (referred to as a propagation time period)
Implementation Method 2
a piezoelectric element 11a included in the sensor 11 to output, as an ultrasonic wave, a voltage signal varying in accordance with a received ultrasonic wave
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A measurement apparatus 100 comprises a measurement unit 10 to propagate, using sensors 11 and 12 provided in a pipe 99, a measurement wave in a medium 98 flowing through the pipe and receive the measurement wave, a trigger detecting section 21 to detect whether or not a level of the received measurement wave exceeds a predetermined trigger level, and a specifying section 22 to specify a reception timing of the measurement wave based on a waveform part in a period of the received measurement wave different from a period in which the level of the received measurement wave exceeds the trigger level.