Development And Experiment Of Stress Vortex Flow Sensor Measurement System

Vortex flow sensor is a kind of sensor applied to the signal detection of vortex flowmeter.Vortex flowmeter is a flowmeter for flow measurement based on Carmen vortex principle.It has a series of advantages,such as no mechanical movable parts in the instrument,reliable operation,simple maintenance,low pressure loss,and the measurement results are not affected by fluid density,temperature,viscosity and other parameters.It has become one of the main flow instruments in the world.Vortex flow sensor is the signal detection device of vortex flowmeter,which can be divided into stress type,thermal type,capacitive type and ultrasonic type according to the measurement method.The stress vortex flow sensor generally adopts piezoelectric sensor,which has the advantages of fast response,low cost and high reliability.It is widely used in vortex flowmeter.This paper takes the stress vortex flow sensor as the research object,and studies the design method of the measurement system.The details are as follows:Design the signal conditioning circuit of the system.Based on the analysis of the output signal characteristics of piezoelectric sensor,a differential charge amplifier with voltage negative feedback is designed to solve the disadvantage of the low frequency performance of traditional charge amplifier restricted by the input bias current and feedback resistance of operational amplifier.Simulation and experimental results show that the improved charge amplifier can effectively reduce the influence of input bias current and feedback resistance,enhance the low frequency signal amplification ability,and play a positive role in broadening the flowmeter range.In view of the traditional bandpass filter bank cannot flexibly adjust the passband frequency and the shortcomings of high cost and high power consumption caused by too many components,a bandpass filter with adjustable center frequency is designed,which greatly simplifies the hardware structure,flexibly adjusts the center frequency according to the needs,improves the filtering effect and reduces the system power consumption.The amplitude limiting amplifier circuit and low-pass filter circuit are used to realize the amplitude limiting and anti-aliasing filtering of flow signal.The temperature and pressure compensation circuit is designed to compensate for the influence of fluid temperature and pressure.Finally,the signal conditioning circuit is shielded to reduce electromagnetic interference.Design the vortex flow sensor measurement system.In order to realize the low-power operation and communication function of the system,and to broaden the application of the system,a wide-range and low-power system design scheme with two power supply modes is proposed.The power management circuit of battery and power supply is designed.At the same time,according to the characteristics and requirements of the two power supply modes,different power supply modes carry out different signal measurement methods and control measures.Design battery protection circuit and charging circuit,and conduct surge protection for external power supply.Build constant current source and reference voltage source to supply power to the corresponding circuit of the system.The ultra-low power MCU MSP430F6459 is used as the core processor,and the corresponding peripheral circuits are built.Design man-machine interface circuit and carry out electrostatic protection.The current output circuit under the two-wire voltage source power supply mode and the corresponding pulse output circuit under the two power supply modes are designed.Design the anti-periodic vibration interference scheme of the system.Taking the common periodic vibration interference of pipeline as the research object,the antiinterference method of the system is analyzed based on the designed hardware circuit,and the corresponding software is designed.In the case of external two-wire power supply,the method based on frequency variance is used to identify the flow signal;In the case of battery power supply,an anti-periodic vibration interference strategy based on controllable bandpass filter is proposed to reduce the amount of calculation of single chip microcomputer and prolong the service life of battery,and the corresponding software of the system is designed.Finally,an experimental platform is built to test the performance of the corresponding modules of the developed system.