Ultrasonic Flow Meter Using Digital Under-Sampling
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Solution Overview
Problem
Existing ultrasonic flow meters face challenges in achieving cost-efficiency and energy efficiency while maintaining accurate time measurements, especially due to the high power consumption and cost of high-speed analogue-to-digital converters (ADCs).
Innovation Solution
The method involves operating the ultrasonic flow meter by generating acoustic wave packets and adding artificial noise, then digitizing the received signals at a sampling frequency below the Nyquist limit to generate under-sampled signals. These signals are processed to determine the difference in propagation time without reconstructing the original signal, reducing the performance demands on the ADC and digital signal processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-speed analogue-to-digital converters are used to achieve accurate time measurements, then measurement precision is improved, but power consumption increases and cost increases
Solution Approach 1:
The patent changes the sampling frequency parameter from high-speed (above Nyquist rate) to low-speed (below Nyquist rate) sampling. This parameter change allows the use of lower-power ADCs while maintaining measurement accuracy through digital signal processing techniques that compensate for the reduced sampling rate.
Solution Approach 2:
The patent replaces the reliance on high-speed hardware ADC performance with digital signal processing algorithms. Instead of using fast ADCs to capture complete waveforms, the system uses processed representations of undersampled signals to determine time of flight, substituting computational methods for hardware performance.
2Measurement precision
If high-speed analogue-to-digital converters are used to achieve accurate time measurements, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent changes the sampling frequency parameter from high-speed to low-speed sampling, enabling the use of cheaper, lower-performance ADCs. This parameter modification directly reduces component cost while maintaining measurement accuracy through digital processing compensation.
Solution Approach 2:
The patent employs inexpensive ADCs that would normally be considered insufficient for accurate time measurement, but compensates through digital signal processing. This approach uses cheaper components to achieve the same functional result, reducing overall device cost.
3Use of energy by moving object
If sampling frequency is reduced below Nyquist limit to lower power consumption, then power consumption is reduced, but signal information is lost
Solution Approach 1:
The patent converts the apparent harm of information loss from undersampling into a benefit by using digital signal processing to extract sufficient information from the reduced data set. The processing algorithms are designed to recover time of flight information even when complete signal reconstruction is not possible.
Solution Approach 2:
The patent extracts only the essential information needed for time of flight measurement from the undersampled signals, rather than attempting to fully reconstruct the original signal. This selective extraction of critical parameters maintains measurement accuracy while working with reduced data from low-speed sampling.
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 determination of propagation time differences using under-sampled signals, leading to a cost-effective and energy-efficient ultrasonic flow meter with extended battery life and minimal impact on measurement accuracy.
Implementation Method 1
at least two ultrasonic transducers arranged for transmission and receipt of ultrasonic signals
Implementation Method 2
arranged for transmission and receipt of ultrasonic signals in opposite directions across a measuring distance
Implementation Method 3
measuring a transit time difference between counter-propagating ultrasonic waves in the medium flow
Data Source
Figure 1~2B
Figure 3A~4C
Figure 5A~6B
AI summary
The invention relates to a method of operating an ultrasonic flow meter by digitally sampling received signals. Acoustic wave packets are transmitted through a measuring distance in opposite directions, and the received signals are digitized at a sampling frequency being below the Nyquist-limit of two times the signal frequency of the wave packet to generate digitized under-sampled signals. From the digitized under-sampled signals, the difference in propagation time along the measuring distance is determined. The accuracy of the measurements are improved by introducing artificial noise into the acoustic wave packets to be transmitted, then compensating for said addition of artificial noise by means of digital signal processing of the received signal, and averaging the determined time difference obtained over a number of measurements.