Vortex shedding flowmeter based on CPLD and correcting method thereof

Abstract

The invention belongs to the technical field of flow measurement, and relates to a CPLD-based vortex shedding flowmeter. The vortex shedding flowmeter comprises a supply voltage conversion circuit, a piezoelectric sensor used for generated vortex shedding signals, a front end signal processing circuit, a standard pulse shaping circuit, the CPLD and a peripheral circuit thereof as well as a crystal oscillator circuit for providing a clock for the CPLD and a precision voltage flow conversion circuit, wherein, the piezoelectric sensor, the front end signal processing circuit and the standard pulse shaping circuit are sequentially connected, and PWM signals output from the standard pulse shaping circuit are sent to the CPLD; the CPLD stores a lookup table which reflects the corresponding relation between the vortex shedding frequencies before and after correction, and the CPLD counts the vortex shedding signals according to the input PWM signals, and corrects a count value by the lookup table to output a frequency signal reflecting the flow rate. The invention also provides a correction method of the flowmeter. The vortex shedding flowmeter and the correction method have the advantages of low power consumption, reliable performance and good real-time property.

Description

technical field [0001] The invention belongs to the technical field of flow measurement, and in particular relates to a vortex flowmeter. Background technique [0002] Flow sensors with frequency signal output such as vortex street and turbine can obtain output signals with good repeatability in a wide flow range. The instrument coefficient of the vortex flowmeter is basically a constant in the normal flow range, but it shows obvious nonlinearity when measuring small flow, which restricts the measurement range and measurement accuracy of the vortex flowmeter. For example, the range ratio of ordinary analog vortex street can only reach 1:10 when the nonlinear error of instrument coefficient is within ±1%, which is far lower than the theoretical range of 1:100. With the development and progress of industrial technology, the demand for wide-range and high-precision flow meters is becoming increasingly urgent, and various non-linear correction methods and applications of meter ...

AI Technical Summary

Problems solved by technology

However, since this method is realized by software compensation, small errors in programming and uncertainties caused by complex conditions on the application site can easily cause the program to deviate from the normal path, resulting in crashes or "running away" of the program, resulting in Instability to use

[0005] The traditional method is to use the average meter coefficient as the only value of the sensor meter coefficient, so that the measurement range of the flow meter is narrow under the premise of ensuring the measurement accuracy

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