Ultrasonic Flow Meter ADC Offsets for Accurate Transit-Time Sensing
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Solution Overview
Problem
Transit-time based ultrasonic flow meters face challenges in accurately measuring transit-times and transit-time differences due to the non-linearity and inaccuracy of medium or low-quality analog-to-digital converters, especially in measuring low-flow rates and broadband signals, which affects the accuracy of flow and volume measurements.
Innovation Solution
The implementation of an analog-to-digital converter arrangement with different input level offsets for each ultrasound measurement signal, allowing for the use of medium or low-quality converters by averaging linearity errors across multiple measurements, thereby improving the robustness against non-linearity and increasing the accuracy of transit-time difference measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution and high-quality analog-to-digital converter with a high sample rate is used to measure ultrasound signals, then measurement precision of transit-time difference is improved, but device cost and energy consumption increase significantly
Solution Approach 1:
The measurement process is segmented into multiple separate ultrasound signal measurements instead of relying on a single high-precision conversion. By taking multiple measurements with different input level offsets and processing them together, the system achieves high effective precision using a medium or low-quality converter that would normally be insufficient for the task.
Solution Approach 2:
The input level offset parameter is varied across multiple measurements to deliberately sample different portions of the ADC transfer function. This parameter change strategy allows the system to average out non-linearity errors and achieve high measurement precision despite using a lower-quality converter with inherent non-linearities.
2Measurement precision
If conventional dithering techniques are applied to improve linearity in low-quality converters, then measurement accuracy is improved, but the technique becomes complicated and may become destructive for small scale, broadband signals sampled at low rate
Solution Approach 1:
Instead of adding complex dithering noise to the signal path, the invention extracts the essential function of linearization by using multiple measurements with different input level offsets. This approach removes the need for complicated dithering circuitry and signal processing while achieving the same linearity improvement goal.
Solution Approach 2:
The system uses multiple disposable measurements with different input level offsets rather than implementing a complex, persistent dithering mechanism. Each measurement can be considered a simple, inexpensive sampling event that contributes to the overall accurate result when processed together, avoiding the need for sophisticated ongoing dithering.
3Measurement precision
If multiple measurements with different input level offsets are taken and processed, then robustness against non-linearity is improved and measurement accuracy increases, but measurement time and processing complexity increase
Solution Approach 1:
The system performs periodic measurements with different input level offsets in a systematic sequence. This periodic approach allows the measurements to be taken and processed efficiently, achieving high accuracy through multiple samples while maintaining a regular, predictable measurement rhythm that minimizes overall time loss.
Solution Approach 2:
The different input level offsets are predetermined and prepared in advance as part of the measurement sequence. This preliminary preparation of the measurement strategy allows the actual measurements to proceed efficiently without real-time decision-making delays, reducing processing time while maintaining the accuracy benefits of multiple offset variations.
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 enhances the average accuracy of transit-time difference measurements and flow representations, reducing errors over time and improving the overall performance of transit-time based flow meters, particularly in low-flow rate and broadband signal conditions.
Implementation Method 1
two ultrasonic transducers mounted relative to the flow of a fluid in such a way that ultrasonic signals can be transmitted at least partially along the flow or against the flow
Implementation Method 2
The transit-time, or time-of-flight, of an ultrasonic signal varies with the direction and fluid flow rate
Implementation Method 3
an analog-to-digital converter arrangement for sampling ultrasound measurement signals from the ultrasonic transducers
Data Source
AI summary
Transit-time based ultrasonic flow meter with analog-to-digital conversion for measuring ultrasonic signals, wherein accuracy of measurements is improved by making several measurements with different input offset, reference voltage, frame offset or sample rate in an analog-to-digital conversion stage.