| Piezoelectric transducer is one of the core contents of ultrasonic technology.It plays a very important role in many fields,such as industry,agriculture,transportation,medical and military.Transducer parameters,which are used to calculate the conversion efficiency of transducers,are the standard parameters to evaluate the performance of devices,and are very important to determine the parameters of matching network.However,the current measurement methods and technologies for transducer parameters have shortcomings in the adaptive matching,integration and measurement efficiency of multi frequency ultrasonic power supply.According to the research on the working mechanism and matching network of the energy converter,combined with the software and hardware design technology,two devices for directly measuring the parameters of the energy converter are designed.According to the different characteristics of transducer equivalent circuit at different frequencies,the measurement schemes based on impedance method and phase method are designed,and the simulation verification and error analysis are carried out respectively.A piezoelectric transducer parameter measurement device based on arm is designed,including hardware circuit design and software program design.The signal generating circuit is used to generate sine wave signals of four specific frequencies and drive the transducer to work;The function of the sampling circuit is to collect the voltage and current values at both ends of the transducer,and keep their values transmitted to the next unit;In addition to calculating the effective value,the peak signal obtained by the peak detection circuit can also be used as the input signal of the phase detection circuit,and the analog multiplier is used to calculate the phase difference of two sine waves;The purpose of A/D conversion circuit is to convert continuous analog input signals into digital signals that can be used by STM32.A stable power module is designed to ensure that the chip is in the best working state;DDS signal source module uses current extremum method to sweep frequency,and writes frequency control words required by different frequencies from STM32 to DDS chip;The function of the data acquisition and processing module is to calculate the equivalent circuit parameters of the converter according to the two algorithms;The display control module completes the design of touch screen and operation keys according to the communication protocol and instruction set adopted by Devon screen.In order to verify the accuracy and practicability of the proposed two parameter measurement methods,a test platform was built to measure the piezoelectric transducers with resonant frequencies of 19kHz～40kHz for many times.Comparing the test results with the impedance analyzer PV520A,it is found that the parameter measurement error of the two methods is less than 2%,the measurement accuracy meets the actual needs,and the stability is good.The basis for the performance matching of the transducer can be given according to the measurement data,so as to realize the automatic matching of the multi frequency transducer. |
