Ultrasonic Flow Meter Algorithm for Low Power Phase Difference Calculation
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Solution Overview
Problem
Existing flow measurement systems face challenges in efficiently calculating the envelope and phase or time difference between signals with high accuracy and low power consumption, especially in battery-operated devices, due to complex sine and cosine calculations and sensitivity to frequency variations and noise.
Innovation Solution
A system and method that use a mathematical model with a reference frequency related to the sample frequency, allowing for simplified calculations by reducing sine and cosine functions to division operations, and employing a Least Square Fit method with a Hanning weight function to achieve fast and robust phase or time difference calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sine and cosine calculations are used to determine phase or time difference, then measurement accuracy is maintained, but power consumption increases and calculation speed decreases
Solution Approach 1:
The patent transforms the calculation parameters by introducing a reference frequency that is a divisor of the sampling frequency. This allows sine and cosine calculations to be replaced with simple division operations and lookup table accesses, dramatically reducing computational complexity and power consumption while maintaining measurement accuracy through the preserved frequency relationship
Solution Approach 2:
The patent creates a simplified computational model that copies the essential frequency relationship without requiring full sine/cosine calculations. By storing pre-calculated values in lookup tables and using division operations to maintain the frequency ratio, the system replicates the phase difference measurement function with minimal computational overhead
2Measurement precision
If traditional sine and cosine calculations are used to determine phase or time difference, then measurement accuracy is maintained, but calculation speed decreases
Solution Approach 1:
The patent changes the computational parameters by establishing a reference frequency that is an integer divisor of the sampling frequency. This transformation converts complex trigonometric calculations into simple division operations and memory lookups, increasing calculation speed by orders of magnitude while preserving the accuracy needed for phase and time difference measurements
Solution Approach 2:
The patent replaces the mechanical computation of sine and cosine functions with an electronic/substitutional approach using division operations and pre-stored lookup tables. This substitution eliminates the need for iterative or complex mathematical computations, achieving fast results suitable for real-time flow measurement applications
3Device complexity
If fixed frequency calculations are used, then calculation simplicity is maintained, but reliability decreases due to sensitivity to frequency variations
Solution Approach 1:
The patent introduces dynamic adaptability by calculating the actual frequency of the received signal and adjusting the reference frequency accordingly. The system maintains the divisor relationship dynamically, allowing it to adapt to frequency variations caused by temperature, humidity, or medium density changes while preserving calculation simplicity through the maintained integer divisor relationship
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual signal frequency and using this information to adjust the reference frequency selection. This feedback mechanism ensures that the divisor relationship is maintained under varying operating conditions, improving reliability without sacrificing calculation simplicity
Data Source
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AI summary
The present invention relates to a method for calculating the flow in a gas or a liquid by an ultrasonic flow meter. It is the object of the pending patent application to achieve a very fast calculation of fluid flow, gas or liquid, in a flow channel. A further object is to achieve calculation of flow with extremely low power consumption of the system calculating the fluid flow. This can be achieved by performing condensing and summarizing of the data by use of a mathematic model in order to fit data to the following general model function g(t) = h(t; a4, a5,..., aM). sin(a1. t + a2) + a3. and by calculating the flow by using either the digital Constant Fraction Discriminator, DCFD, using a part of, or all, of the data frame or by Least Square Fit (LSQF) by fitting measured data to a model function of the type g(t) = h(t; a4, a5,..., aM). sin(a1 . t + a2) + a3, or a combination of DCFD and LSQF for achieving at least Ta, Tb and DT. The use of a mathematical model calculating further in the system using the model will give a function that still contains the necessary transmission times Ta and Tb as well as time difference DT.