Ultrasonic Signal Sampling Using Time-Offset Segmentation
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Solution Overview
Problem
Ultrasonic flow meters face challenges in reconstructing high-frequency ultrasonic signals due to the limitations of low-cost microcontrollers' analog-to-digital converters, which cannot sample at the required Nyquist rate, leading to undersampling and inadequate signal digitization for accurate diagnostics.
Innovation Solution
A method involving repeated transmission and reception of ultrasonic signals with varying sampling start times and frequencies, allowing for the combination of digital samples to achieve a higher effective sampling frequency, enabling high-resolution signal reconstruction using relatively inexpensive analog-to-digital converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-cost microcontrollers with integrated analog-to-digital converters are used, then system cost is reduced, but sampling frequency is insufficient to meet Nyquist rate requirements for high-frequency ultrasonic signals
Solution Approach 1:
The sampling process is segmented into multiple sequential sampling operations instead of requiring a single high-speed sampling operation. The ultrasonic signal is sampled multiple times at different time offsets using the low-frequency ADC, and these segmented samples are later combined to reconstruct the high-frequency signal effectively
Solution Approach 2:
The system performs periodic sampling at a lower frequency multiple times with varying time offsets. By repeating the sampling process periodically with different start times and combining the results, the system achieves effective high-frequency signal reconstruction without requiring the ADC to operate at the full Nyquist rate
2Device complexity
If undersampling is used to match ADC capabilities, then hardware requirements are simplified, but signal digitization accuracy is insufficient for effective diagnostics
Solution Approach 1:
The system transitions from a single-dimension sampling approach (single high-speed sample) to a multi-dimensional approach by introducing time offset as an additional dimension. Multiple samples taken at different time offsets create a more comprehensive representation of the ultrasonic signal, enabling accurate reconstruction and diagnostics
3Measurement precision
If expensive high-frequency analog-to-digital converters are used to completely reconstruct the signal, then signal reconstruction accuracy is improved, but system cost increases significantly
Solution Approach 1:
Instead of using a single expensive high-frequency ADC, the system creates multiple copies of the low-frequency ADC sampling process with different time offsets. By combining these multiple low-cost sampling copies, the system achieves the equivalent measurement precision of a single expensive high-frequency converter
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 accurate high-resolution digitization of ultrasonic signals, improving flow speed measurements and enabling effective diagnostics without the need for expensive equipment, by effectively increasing the sampling frequency beyond the limitations of standard converters.
Implementation Method 1
transforming the input electric signal to an ultrasonic signal
Implementation Method 2
transforming the received ultrasonic signal at the second ultrasonic transducer to an output electric signal
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method and a system (1 ) for sampling an ultrasonic signal, comprising two ultrasonic transducers (2, 3) arranged in a fluid path connected to a control unit (4). Task of the invention is to provide a method and a system for sampling an ultrasonic signal that allows to obtain a higher resolution digital output signal without the need for an analog-to-digital converter with a high sampling frequency. The task is solved by a method comprising the following steps: a) Sending an input electric signal from the control unit (4) to a first ultrasonic transducer (2), transforming the input electric signal to an ultrasonic signal and sending it to a second ultrasonic transducer (3) through the flow path, b) transforming the received ultrasonic signal at the second ultrasonic transducer (3) to an output electric signal that is sent to the control unit (4), c) sampling the output electric signal received at the control unit to a first series of digital samples at a sampling frequency, d) repeating steps a) to c) at least once with the same electric input electric signal, wherein in step c) the time of start of the sampling measured from the time of start of the respective input electric signal and/or the sampling frequency is different from the previous sampling, e) combining the obtained series of samples to obtain a combined digital output signal.