Reasearch And Design Of Testing Method For Piezoelectric Ultrasonic Transducer

Ultrasonic flowmeter is widely used in water,heat and gas flow measurement,in which ultrasonic transducer is the core component of ultrasonic flowmeter.In the practical application of flow measurement,time difference method is the use of a test method for the most.Ultrasonic transducers applied in the time difference method need to be used in pairs,and the performance matching directly affects the flow measurement accuracy of the time difference method ultrasonic flowmeter.There is no unified technical standard on rating the performance of transducers used in ultrasonic flowmeter at present.Many company producing flowmeters are used to match transducers by experience instead of researching the parameters matching.Aiming at the poor consistency of ultrasonic transducer's main parameters,this paper studied the test of ultrasonic transducer's main parameters,raised test method of six parameters including the resonant frequency,anti-resonant frequency,resonant impedance,anti-resonant impedance,output amplitude and the static capacitance.in order to provide the matched performance transducers.The main contents of this paper are as follows:Firstly,starting from the working principle of ultrasonic flowmeter,this paper analyzed factors that affect the measuring accuracy of time difference method ultrasonic flowmeter.This paper mainly analyzed the effect of ultrasonic signals on the quality of the signal when transmitted in a fluid,the effect of ultrasonic signals on the accuracy of the scheme which associates threshold detection with zero-crossing detection and so on.Secondly,this paper built an equivalent circuit of a thin wafer thickness vibration,and simulated the Transceiver Features of transducers through MATLAB and mathematical method,thereby analyzed the effect of the resonant frequency,anti-resonant frequency,resonant impedance,anti-resonant impedance and the static capacitance on the output amplitude,which provided theoretical basis to performance consistence of transducers.Finally,this paper built a transducer parameter test device based on FPGA.Aiming at the transmission circuit method requiring signal generator a wide frequency range output,based on digital direct frequency synthesis method,this paper designed a signal generator with a wide frequency range output.Aiming at drive signal frequency unable to adjust and requiring reading data manually during the output amplitude measurement,this paper used variable frequency drive signal to measure the output amplitude.In order to solve the problem of low measuring speed and low anti stray capacitance ability when using LCR digital electric bridge to measure static capacitance,this paper use capacitive reactance method to measure static capacitance,with functions of high speed measurement and automatic zero set.The performance of the transducer is evaluated by measuring the parameters of the transducer,so that the performance matching of the transducer can be achieved.The experimental results show that the parameter measurement methods used in this paper meet the design requirements.By testing the six parameters of the transducer,the performance consistence of the matched transducer is verified.The temperature stability of the transducer parameters is verified by measuring the transducer parameters at different temperatures.