CN110631665A - A piezoelectric ultrasonic transducer testing system and method - Google Patents

Abstract

The invention discloses a piezoelectric ultrasonic transducer testing system and method. A piezoelectric ultrasonic transducer testing system includes a host computer, an ultrasonic transducer tester, and a tooling bracket; the host computer and the ultrasonic transducer The ultrasonic transducer tester is connected with the ultrasonic transducer to be tested; the ultrasonic transducer to be tested is set in the test hole of the tooling bracket; the tooling bracket is located in the container containing water; a piezoelectric The method for the type ultrasonic transducer test system comprises the following steps: open the host computer; configure the port number on the host computer, establish the connection between the host computer and the ultrasonic transducer tester; carry out equipment data marking on the ultrasonic transducer to be tested accordingly , pass marks. The invention realizes single-device ultrasonic transducer detection through one machine multi-parameter test, improves the performance and production efficiency of the ultrasonic transducer test system; and can store the test data of the measured ultrasonic transducer.

Description

A piezoelectric ultrasonic transducer testing system and method

technical field

The invention relates to a testing system and method, in particular to a piezoelectric ultrasonic transducer testing system and method, belonging to the field of measurement and control technology and ultrasonic measurement.

Background technique

Piezoelectric ultrasonic transducers are important components of ultrasonic flowmeters such as ultrasonic water meters and heat meters. Most manufacturers focus on the mechanical structure design of the base meter of the flowmeter, and only a few involve the output signal processing of the flow sensor. . The research on the performance of the flow sensor-ultrasonic transducer is generally ignored, and some companies even lack the necessary understanding of the main technical parameters. The technical parameters provided by more than half of the ultrasonic transducer manufacturers have obvious errors; or are too simple, and the main parameters are not provided; or the name is not true, and the actual measurement results deviate greatly. For example: the center frequency of the ultrasonic transducer of almost all heat meters is nominally 1MHz. The measured result is: only 30% reached (1±0.05) MHz, and the largest deviation exceeded 12%.

Ultrasonic transducers are the key components for ultrasonic flowmeters to measure liquid flow rates. Piezoelectric ceramic-based transducers have more than 20 performance parameters that directly affect the measurement accuracy of heat meters. At present, the production level of piezoelectric ceramics and ultrasonic transducers used in ultrasonic heat meters in China is uneven, resulting in poor consistency of the produced products in terms of structural size and performance parameters. And there are problems such as narrow bandwidth, large pulse reverberation, and resonance frequency deviation, which seriously affect the measurement accuracy and service life of the ultrasonic flowmeter.

Ultrasonic flowmeters have been widely used in flow measurement of water, heat and gas, among which piezoelectric ultrasonic transducers are the core components of ultrasonic flowmeters. In actual flow measurement applications, the time difference method is the most widely used test method. The transducers used in the transit-time ultrasonic flowmeter need to be used in pairs, and their performance matching directly affects the flow measurement accuracy of the transit-time ultrasonic flowmeter.

At present, domestic transducer manufacturers generally use a digital frequency characteristic tester to measure the amplitude-frequency characteristic curve of the transducer, so as to measure the resonant frequency and anti-resonant frequency of the transducer. This test method has a high frequency test accuracy. , but the measured data needs to be read and recorded manually, which is not conducive to storage and the cost is high.

The equivalent impedance test generally adopts the constant voltage source transmission line method. The test principle of this method is simple, but the test requires the use of oscilloscopes, signal sources, precision resistance boxes, millivolt meters and other test instruments, which are manually operated and costly.

The amplitude test uses a single-chip microcomputer to generate a 1MHz pulse excitation signal to excite the transducer. By observing the amplitude of the transmitting and receiving signals of the transducer, it is evaluated whether the transducer can meet the application requirements and paired according to the amplitude. The test method has a single excitation signal, complex operation, and low efficiency. The use of an oscilloscope increases additional costs, and requires experienced engineers to manually adjust the oscilloscope and read, which is likely to cause large reading errors.

To sum up, the current piezoelectric ultrasonic transducer testing system still has the following problems: 1. The cost of special testing instruments in ultrasonic transducer performance testing is high; 2. The indicators of instrument testing are single, and one device cannot test multiple 3. The resonance and anti-resonance impedance test is cumbersome and inefficient; 4. There is no host computer for the piezoelectric ultrasonic transducer, and the test parameters of the transducer cannot be stored.

Contents of the invention

In order to solve the shortcomings of the above-mentioned technologies, the present invention provides a piezoelectric ultrasonic transducer testing system and method.

In order to solve the above technical problems, the technical solution adopted in the present invention is: a piezoelectric ultrasonic transducer test system, including a host computer, an ultrasonic transducer tester, and a tooling bracket; the host computer is connected to the ultrasonic transducer tester connection; the ultrasonic transducer tester is connected with the ultrasonic transducer to be tested; the ultrasonic transducer tester performs parameter detection of the ultrasonic transducer to be tested, and the parameter test includes static parameters: resonant frequency, anti-resonant frequency, resonant impedance, Anti-resonance impedance; dynamic parameters: transmission amplitude and reception amplitude; the ultrasonic transducer to be tested is set in the test hole of the tooling bracket; the tooling bracket is located in a container filled with water;

The ultrasonic transducer tester includes a main control module; the main control module is connected with the clock reset module, power module and configuration module respectively; the main control module is connected with the communication module; one end of the communication module is connected with the touch screen, and the other end is connected with the upper The main control module is connected with the control circuit; one end of the control circuit is connected with the constant current source circuit, and the other end is connected with the circuit under test; the circuit under test is connected with the signal conditioning module; the signal conditioning module passes through A/ The D module is connected with the main control module.

Further, the frequency of the excitation signal output by the ultrasonic transducer tester is adjustable and the adjustable range is 1KHZ-100MHZ; the ultrasonic transducer tester is connected with the host computer through RS232 communication.

Further, the main control module is an FPGA chip whose model is EP2C8Q208C8N; the model of the A/D module is a high-speed A/D converter AD9244; the model of the touch screen is an industrial serial port screen of DC80480B070_03T/NW.

Further, the material of the tooling bracket is 304 stainless steel; the reflective surface finish at the bottom of the tooling bracket is less than 3.2; the height of the tooling bracket is 30-50mm.

A method for testing a piezoelectric ultrasonic transducer testing system, the method for using the testing system comprises the following steps:

A. Turn on the upper computer;

B. Connect the ultrasonic transducer tester with the host computer through the serial port line;

C. Put the tooling bracket into a container filled with water, put the ultrasonic transducer to be tested into the test hole of the tooling bracket, and adjust the temperature of the water in the container according to the test needs;

D. Connect the ultrasonic transducer tester to the ultrasonic transducer to be tested, and the positive and negative poles of the lead wires of the ultrasonic transducer to be tested should correspond to the signal output polarity of the ultrasonic transducer tester;

E. Configure the port number on the host computer, and establish the connection between the host computer and the ultrasonic transducer tester;

F. Select the performance test in the host computer, detect the resonance, anti-resonance frequency, resonance, anti-resonance impedance, transmission amplitude, and reception amplitude information of the ultrasonic transducer to be tested, and perform data on the transmission amplitude and reception amplitude Processing, according to which the ultrasonic transducer to be tested is marked with equipment data and qualified.

Further, the usage method of the ultrasonic transducer tester is:

I. Power on: Turn on the power switch of the ultrasonic transducer tester, and its display screen is a touch operation screen;

II. Connection: Connect the ultrasonic transducer tester to the ultrasonic transducer to be tested;

III. Enter the corresponding detection page by clicking the touch screen on the touch screen: provide three function options: resonance and anti-resonance frequency detection, resonance impedance and anti-resonance impedance detection, transmission amplitude and reception amplitude detection;

IV. Resonance and anti-resonance frequency test: switch the test item switch to the frequency impedance side, select resonance and anti-resonance frequency detection, input the initial scan frequency and end scan frequency, the minimum initial value is 500KHZ, and the maximum end value It is 2500KHZ; after setting the sweep frequency range and clicking the OK button, the resonance frequency and anti-resonance frequency of the device under test will be displayed, and clicking the frequency curve will enable real-time observation of the waveform of the frequency sweep;

V. Resonance and anti-resonance impedance test: Enter the impedance detection selection page, select the resonant impedance or anti-resonance impedance to be tested, the resonance impedance detection needs to use the resonant frequency value of the device, and the anti-resonance impedance detection needs to use the anti-resonance frequency value of the device.

Further, the specific process of the resonance impedance test in step V is as follows: select the resonance impedance detection option and enter the resonance impedance test page. At this time, the test item switching switch needs to be switched to the impedance frequency side. The specific steps are as follows:

a. Input the resonance frequency of the ultrasonic transducer to be tested;

b. Click the amplitude confirmation button to confirm the amplitude at the current resonance frequency;

c. Adjust the impedance adjustment button to make the equivalent amplitude equal to the confirmed amplitude in the previous step;

d. Click the adjustment confirmation button to confirm that the current equivalent amplitude adjustment is completed, and read the resonance impedance.

Further, the main control module multiplies the clock frequency to 300M by first multiplying the frequency and then divides the frequency, and generates a square wave signal of 1KHz-100MHz by using the look-up table method.

The invention adopts multi-frequency scanning technology through the ultrasonic transducer tester, can automatically generate excitation signals of different frequencies, and does not need to connect other testing equipment such as a frequency sweeper, a precision resistance box, etc., and realizes a single device for ultrasonic transducer detection change. The invention can test parameters such as the transmitting and receiving amplitude, resonance and anti-resonance frequency, resonance impedance and anti-resonance impedance of the piezoelectric ultrasonic transducer through a machine, and improves the performance and production efficiency of the ultrasonic transducer testing system ; And through the measurement and screening of ultrasonic transducers, ultrasonic transducer products with superior performance and matching parameters can be obtained for ultrasonic flowmeter products. The design has low cost, multi-parameter test and can store the test data of the measured ultrasonic transducer, with simple operation, high precision and easy data management.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of the present invention.

Figure 2 is a block diagram of the ultrasonic transducer tester system connection.

Figure 3 is a schematic diagram of the power module circuit.

Figure 4 is a schematic diagram of the configuration module circuit.

Figure 5 is a schematic diagram of the constant current source circuit.

Figure 6 is a schematic diagram of a precision full-wave rectification circuit.

Fig. 7 is a circuit schematic diagram of a second-order voltage-controlled voltage source low-pass filter.

Figure 8 is a schematic diagram of the analog-to-digital conversion circuit.

Fig. 9 is a flow chart of excitation signal generation.

Figure 10 is a flow chart of the frequency sweep.

Fig. 11 is a flow chart of continuous excitation signal generation.

Fig. 12 is a flow chart of discontinuous excitation signal generation.

Fig. 13 is a schematic diagram of sampling allowable time for various test items.

Fig. 14 is a flow chart of one sampling data output.

Figure 15 is a schematic plan view of the tooling bracket.

Figure 16 is a schematic diagram of the crystal oscillator circuit.

Figure 17 is a schematic diagram of the reset circuit.

In the figure: 1. Host computer; 2. Ultrasonic transducer tester; 3. Tooling bracket; 4. Ultrasonic transducer to be tested.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

A piezoelectric ultrasonic transducer test system as shown in Figure 1 and Figure 2, including a host computer 1, an ultrasonic transducer tester 2, and a tooling bracket 3; the host computer 1 and the ultrasonic transducer tester 2 are in phase Connection; the ultrasonic transducer tester 2 is connected with the ultrasonic transducer 4 to be tested; the ultrasonic transducer tester 2 performs parameter detection on the ultrasonic transducer 4 to be tested, and the parameter test includes static parameters: resonant frequency, anti-resonant frequency , resonant impedance, anti-resonant impedance; dynamic parameters: transmitting amplitude and receiving amplitude; the ultrasonic transducer 4 to be tested is set in the test hole of the tooling bracket 3; the tooling bracket 3 is located in a container filled with water;

Ultrasonic transducer tester 2 comprises main control module; Main control module is connected with clock reset module, power supply module, configuration module respectively; Main control module is connected with communication module; One end of communication module is connected with touch screen, the other end is connected with The upper computer is connected to 1 phase; the main control module is connected to the control circuit; one end of the control circuit is connected to the constant current source circuit, and the other end is connected to the circuit under test; the circuit under test is connected to the signal conditioning module; the signal conditioning module passes through The A/D module is connected with the main control module. Wherein, the tested circuit refers to the ultrasonic transducer 4 to be tested; the communication module refers to the RS232 communication interface.

The important performance indicators of transducers used in ultrasonic flowmeters include resonant frequency and anti-resonant frequency, resonant impedance and anti-resonant impedance, and emission intensity. These indicators can comprehensively reflect the performance of the transducer, and provide a basis for performance evaluation of the ultrasonic transducer and the pairing of the transducer. The ultrasonic transducer tester 2 is designed around these parameters.

Ultrasonic transducer tester 2 is designed with FPGA as the main control chip, and the test items are selected through touch screen control. The FPGA model chooses EP2C8Q208C8N chip, and the touch screen adopts industrial serial port screen, the model is DC80480B070_03T/NW. FPGA is used as an excitation signal source to generate the excitation signals required by each test item. Since some circuits between each test item are the same, analog switches and mechanical switches are used to realize circuit multiplexing to reduce the design PCB (printed circuit board) area. Analog switches Controlled by FPGA. The response signal generated by each test item is rectified and amplified by the signal conditioning circuit to obtain a signal suitable for A/D sampling. According to the frequency and amplitude change of the test signal, this design uses a high-speed A/D converter AD9244 for Data sampling. The FPGA preprocesses the data after A/D conversion to obtain the test results of each test item, and sends the test results to the touch screen in real time for display. The test data is sent to the upper computer 1 through the RS232 communication interface, and the upper computer 1 is used to process and store the test data. The overall design block diagram is shown in Figure 2.

The clock reset module is the clock and reset circuit module: the clock circuit is the crystal oscillator circuit, and the crystal oscillator circuit provides an accurate reference clock. Since an excitation signal of 500KHz to 2.5MHz needs to be generated by the FPGA, a reliable and accurate clock signal is required, so the crystal oscillator chooses 50MHz Active crystal oscillator with an accuracy of 10PPM. As shown in Figure 16. As shown in Figure 17, the reset circuit has two purposes. The first is when the FPGA program runs away or an abnormal phenomenon occurs, the reset circuit is used to reset the program and let the program run from the beginning; the second is to replace When the other ultrasonic transducer 4 to be tested is tested, the program parameters are initialized through the reset key. Since the FPGA itself has its own power-on reset circuit, the peripheral reset circuit mainly realizes the initialization of program parameters.

The power module is used to provide corresponding voltage to FPGA and other devices. FPGA needs 3.3V I/O port standard voltage and 1.2V core power supply voltage, A/D converter, touch screen, etc. need 5V voltage power supply, configuration chip needs 3.3V power supply. The schematic diagram of the power module circuit is shown in Figure 3.

The ultrasonic transducer tester 2 configuration module includes a configuration chip and a configuration interface. The configuration chip is used to store the application program of the FPGA. If the chip is not configured, the program downloaded to the FPGA through the JTAG interface will be lost when the power is turned off, and the program needs to be downloaded again after each power-on. The configuration chip selects the EPCS4 series that matches the EP2C8 series FPGA, the specific model is EPCS4SI8N, the capacity is 4Mbits, and it can be reprogrammed. The configuration module EPCS4SI8N chip communicates with FPGA through serial mode. The four signals of the EPCS4 chip, the serial clock input (DCLK), the serial data output (DATA), the chip select signal (nCS) and the AS control signal input (ASDI) are the four pins of the EPCS4 chip, which are connected to the FPGA respectively. Four pins: DCLK, DATA0, nCSO and ASDO are connected. The schematic diagram of the configuration module circuit is shown in Figure 4.

Ultrasonic transducer tester 2 control circuit is divided into automatic control and manual control. The automatic control part controls two analog switches 74HC4053 through FPGA to switch the circuit to control the direction of the signal; the manual control part is realized through two double-pole double-throw mechanical switches. Since the on-resistance exists when the analog switch is turned on, the on-resistance has a great influence on some test items of the ultrasonic transducer tester 2, while the on-resistance of the mechanical switch is very small and can usually be ignored. One of the two mechanical switches in the ultrasonic transducer tester 2 is used to switch between the test items of the amplitude of the transmitted signal and the received signal and the other two test items, and the other is used to switch the constant current source circuit to test the impedance of different ranges .

The testing range of the equivalent impedance of the ultrasonic transducer tester 2 is 0-5.5KΩ. The resonance impedance of the ultrasonic transducer used in the ultrasonic flowmeter is small, generally less than 100Ω; the anti-resonance impedance is large, but generally not more than 3KΩ. R11, R12, R13, and R14 in Figure 5 form a resistance bridge. The operational amplifier U7B is a voltage follower with high input impedance. It can be seen that the potential difference between points A and B is 1.2V. When the triode is in the enlarged state , the circuit is capable of producing a constant current. When the Y0 channel of the analog switch U6 is turned on, the constant current source current flows through R20 and the resistance Rx to be measured. If Rx is too large, the triode will enter a saturated state and cannot achieve constant current, so when Rx is greater than 1.5KΩ, a mechanical switch is used to switch to a small current state. The current of the constant current source is I=1.2V/R, when the switch is on the R17 side, I1=1mA, and the 129 pin of the FPGA is low at this time; when the switch is on the other side, I2=0.2mA, and the 129 pin of the FPGA is high at this time . FPGA distinguishes the current of the constant current source according to the high and low levels of pin 129, and thus uses different algorithms to calculate the resistance value. When testing the resonant impedance and anti-resonant impedance of the transducer, in order to avoid the problem of low efficiency caused by manual recording and storage, a constant current source circuit is introduced to realize the automatic reading and storage of equivalent impedance.

The function of the signal conditioning module is to rectify, filter and amplify the response signal obtained by the excitation transducer to obtain a signal suitable for A/D sampling, including a rectification circuit and a filter circuit. The rectification circuit adopts a precision full-wave rectification circuit with single-ended input to realize full-wave rectification. The schematic diagram of the precision full-wave rectification circuit is shown in Figure 6. Select R21＝R22＝R24＝R25＝2R23＝1KΩ in the rectification effect tester. In order to prevent high-frequency interference in the circuit, it is necessary to filter the rectified signal with a low-pass filter. The second-order voltage-controlled voltage source low-pass filter is selected as the filter circuit of the signal conditioning module, as shown in Figure 7.

The A/D module is an important part of the entire tester, as shown in Figure 8. Convert the analog signal after rectification, filtering and amplification into digital signal and send it to FPGA for processing. The analog-to-digital converter selected by the ultrasonic transducer tester 2 is a high-speed A/D converter AD9224. In order to avoid the influence of the input impedance of the A/D converter and enhance the driving capability, a voltage follower is added to the front end of the analog input.

The frequency of the excitation signal output by the ultrasonic transducer tester 2 is adjustable and the adjustable range is 1KHZ-100MHZ; the ultrasonic transducer tester 2 is connected with the host computer 1 through RS232 communication. Ultrasonic transducer tester 2 is one of the most important components in the test system. It mainly completes the generation of excitation signals, receives signal feedback from the ultrasonic transducer 4 to be tested and analyzes the physical indicators of the transducer, and obtains The data is transmitted to the host computer 1 for subsequent use.

Ultrasonic transducer tester 2 is the core of the entire test system. As the excitation signal generator for each test item, it also performs data collection, processing and display at the same time. It can send test data and results to the host computer 1, and can also be separated from the host computer. 1 work independently.

Ultrasonic transducer tester 2 can detect the resonant frequency and anti-resonant frequency, resonant impedance and anti-resonant impedance in one machine, and can measure the dynamic parameters of the transducer (receiving amplitude and transmitting amplitude), and simulate the actual work of the transducer The parameters at the time, so as to judge whether the transducer is qualified by comprehensively transmitting and receiving the signal amplitude of the ultrasonic transducer 4 to be tested, and two transducers with similar parameters can be used together in several transducers that have been judged to be qualified , contribute to the performance stability of the final product. The ultrasonic transducer tester 2 uses FPGA as the main controller, and uses serial port communication to realize data transmission with the host computer 1, and the host computer 1 processes the test data.

The upper computer 1 provides a simple and clear user operation interface. Through the test data stored in the upper computer 1, the user can intuitively understand whether the ultrasonic transducer 4 to be tested meets the selection criteria, and the user can flexibly exchange it according to his own needs. Adjust the selection criteria of the transducer, and through the test data, it is convenient to select the transducer equipment with similar indicators. The upper computer 1 analyzes and calculates the test data, and outputs qualified ultrasonic transducer data. The upper computer 1 stores and processes the test data from the transducer tester. The performance detection item in the host computer is to store and process the receiving and transmitting amplitudes, and the parameter test item is to store the resonant frequency, anti-resonant frequency, impedance, etc. of the transducer.

The main control module is an FPGA chip of model EP2C8Q208C8N; the model of A/D module is high-speed A/D converter AD9244; the model of touch screen is industrial serial port screen of DC80480B070_03T/NW.

FIG. 15 is a schematic plan view of the tooling bracket 3 . The tooling bracket 3 is used to clamp the ultrasonic transducer 4 to be tested, and can be placed in water of different temperatures to simulate and test the performance parameters of the ultrasonic transducer 4 to be tested in water of different temperatures. The tooling bracket 3 is made of 304 stainless steel; the reflective surface finish at the bottom of the tooling bracket 3 is less than 3.2; the path of the simulated ultrasonic wave in the actual product application, that is: after the ultrasonic wave is sent from the bottom surface of the ultrasonic transducer 4 to be tested, the test tooling The reflective surface at the bottom of the bracket 3 is reflected and then received by the ultrasonic transducer 4 to be tested. The path length of the ultrasonic wave should be equal to the distance traveled by the ultrasonic wave in the forward and reverse paths of the ultrasonic flowmeter product. The height of tooling support 3 is 30-50mm. The test tooling bracket 3 is made of special stainless steel material, especially used as the bottom plane of the emitting surface. The distance from the upper plate of the bracket to the reflection surface of the bottom plate can be adjusted so that the lower bottom plane of the ultrasonic transducer 4 to be tested is in line with the test tooling bracket 3 The distance of the bottom reflective surface fully complies with the actual working distance of the ultrasonic transducer in the ultrasonic heat meter.

A method for testing a piezoelectric ultrasonic transducer testing system, the method for using the testing system comprises the following steps:

A. Turn on the upper computer 1;

B. Connect the ultrasonic transducer tester 2 with the host computer 1 through the serial port line;

C. Put the tooling bracket 3 into a container filled with water, put the ultrasonic transducer 4 to be tested into the test hole of the tooling bracket 3, and adjust the temperature of the water in the container according to the test needs;

D, the ultrasonic transducer tester 2 is connected with the ultrasonic transducer 4 to be tested, the positive and negative poles of the ultrasonic transducer 4 leads to be tested should correspond to the signal output polarity of the ultrasonic transducer tester 2;

E. Configure the port number on the host computer 1, and establish the connection between the host computer 1 and the ultrasonic transducer tester 2;

F. Select the performance test in the host computer 1 to detect the resonance and anti-resonance frequency, resonance, anti-resonance impedance, emission amplitude, and reception amplitude information of the ultrasonic transducer 4 to be tested, and to transmit and receive the amplitude. The data is processed, and accordingly the ultrasonic transducer 4 to be tested is marked with equipment data and qualified.

The ultrasonic transducer tester 2 mainly obtains the resonance and anti-resonance frequency, resonance, anti-resonance impedance, transmission amplitude, and reception amplitude information of a single transducer, and transmits the information obtained by the testing instrument to the host computer 1 for storage. And the parameter analysis of the transducer can be carried out according to the receiving amplitude and other parameters.

The method of using the ultrasonic transducer tester 2 is as follows:

I. start: open the power switch of ultrasonic transducer tester 2, its display screen is a touch operation screen;

II. Connection: connect the ultrasonic transducer tester 2 with the ultrasonic transducer 4 to be tested;

III. Enter the corresponding detection page by clicking the touch screen on the touch screen: provide three function options: resonance and anti-resonance frequency detection, resonance impedance and anti-resonance impedance detection, transmission amplitude and reception amplitude detection;

IV. Resonance and anti-resonance frequency test: switch the test item switch to the frequency impedance side, select resonance and anti-resonance frequency detection, input the initial scan frequency and end scan frequency, the minimum initial value is 500KHZ, and the maximum end value It is 2500KHZ; after setting the sweep frequency range and clicking the OK button, the resonance frequency and anti-resonance frequency of the device under test will be displayed, and clicking the frequency curve will enable real-time observation of the waveform of the frequency sweep;

V. Resonance and anti-resonance impedance test: Enter the impedance detection selection page, select the resonant impedance or anti-resonance impedance to be tested, the resonance impedance detection needs to use the resonant frequency value of the device, and the anti-resonance impedance detection needs to use the anti-resonance frequency value of the device.

The specific process of the resonance impedance test in step V is as follows: select the resonance impedance detection option and enter the resonance impedance test page. At this time, the test item switch needs to be switched to the impedance frequency side. The specific steps are as follows:

a. input the resonant frequency of the ultrasonic transducer 4 to be tested;

b. Click the amplitude confirmation button to confirm the amplitude at the current resonance frequency;

c. Adjust the impedance adjustment button to make the equivalent amplitude equal to the confirmed amplitude in the previous step;

d. Click the adjustment confirmation button to confirm that the current equivalent amplitude adjustment is completed, and read the resonance impedance.

The measurement of anti-resonant impedance is basically the same as the measurement of resonant impedance. There are two differences: first, the anti-resonant impedance requires the input frequency to be the anti-resonant frequency of the device under test. Second, due to the large anti-resonant impedance, if the equivalent amplitude is adjusted to the maximum by adjusting the impedance knob, it is still smaller than the amplitude of the current frequency, you need to switch the impedance range switch to 5KΩ.

The main control module adopts the method of frequency multiplication first and then frequency division, multiplies the clock frequency to 300M, and applies the look-up table method to generate a square wave signal of 1KHz-100MHz.

Ultrasonic transducer tester 2 generates different excitation signals required by each test item through FPGA, and the required excitation signals can be divided into sweep frequency excitation signals, continuous excitation signals and intermittent excitation signals.

The 50MHz clock frequency of the system is multiplied to 200MHz through the PLL IP core that comes with the FPGA, and then the 200MHz frequency is divided to obtain an excitation signal of 500KHz to 2.5MHz with a step distance of 10KHz. The flow chart of excitation signal generation is shown in Figure 9.

Among them, f_out is the actual output excitation signal, which is configured to pin 138 of the FPGA; send_en is the sending excitation enable signal. When the sending enable signal is low, the output f_out is in a high-impedance state, and when the sending excitation enabling signal send_en is high, Output the excitation signal f_out_r obtained by frequency division.

When testing the resonant frequency and anti-resonant frequency of the transducer, the FPGA needs to send a frequency-sweeping excitation signal with a variable frequency in the range of 500KHz to 2.5MHz. The default frequency sweep range of the tester is 500KHz, and the cutoff frequency is 2.5MHz. The range of the excitation signal can be set arbitrarily on the basis of 10KHz step distance through the touch screen. The frequency scanning flow chart is shown in Figure 10.

When testing the resonant impedance and anti-resonant impedance of the transducer, the FPGA needs to send a continuous excitation signal with a fixed frequency, and the frequency of the excitation signal is set through the touch screen. The frequency does not change during the whole process of testing the impedance, and the continuous excitation signal generation process is shown in Figure 11.

When testing the amplitude of the transmitting and receiving signals of the transducer, the FPGA needs to send a fixed-frequency intermittent excitation signal. After sending the excitation signal for a period of time, it needs to be delayed for a period of time to bypass the echo signal to prevent the emission signal and the echo signal from being superimposed. . The duration of the excitation signal is related to the height of the test fixture support 3 . For example, the tooling bracket 3 used by the ultrasonic transducer tester 2 has a height of 40mm, and the propagation speed of ultrasonic waves in water is about 1500m/s, so an echo signal returns to the transducer about 53μs after the excitation signal is sent out. An excitation signal of 50 μs is sent at a time. The flow chart of discontinuous excitation signal generation is shown in Figure 12.

The sampling frequency of AD9224 used by Ultrasonic Transducer Tester 2 is 20MHz. The clock of the analog-to-digital conversion module is a 40MHz clock obtained by multiplying 50MHz by four times and dividing by five through the FPGA internal phase-locked loop, and then divides 40MHz by two to output 20MHz As A/D sampling clock.

The sampling time of different test items in the ultrasonic transducer tester 2 is different. When testing the resonant frequency and anti-resonant frequency, the excitation signal is a frequency sweep signal, which is sampled at 10 μs in the middle of each frequency point; when testing the resonant impedance and anti-resonant impedance First sample for 50ms and then sample for 10μs, and continue to cycle; when testing the amplitude of the transmitted signal and received signal, in order to avoid the oscillation and attenuation of the signal, the sampling is performed in the middle of 10μs between the transmitted signal and the received signal. The sampling time is controlled by controlling the sampling allowable signal oe_n, and the schematic diagram of the sampling allowable time of each test item is shown in Fig. 13 .

Among them, sp_mid is the middle moment of each frequency point of the frequency sweep excitation signal, and send_mid and hb_mid are the middle moments of the sending signal and the echo signal respectively.

The frequency range of the excitation signal of the tester is 500KHz to 2.5MHz, the sampling frequency of the A/D converter is 20MHz, and the sampling times per cycle of each frequency point ranges from 8 to 40 times. The flow chart of one sampling data output is shown in Figure 14.

The upper computer 1 will automatically receive the test data uploaded by the ultrasonic transducer tester 2, and the user can intelligently filter the data collected by the current function according to the currently used test function. The data storage of the upper computer 1 adopts SQLite database.

For the qualification standards of ultrasonic transducers, the requirements of different manufacturers are not uniform. In order to meet different test standards, the qualified parameters of the transducer can be adjusted flexibly: the emission amplitude, reception amplitude and test water temperature can be adjusted. Ultrasonic transducers are used in pairs, and the transducers used in pairs in ultrasonic flowmeters need to be as close as possible in physical properties, and the matching standards can be adjusted according to user requirements.

The ultrasonic transducer test system has a small amount of data, and the database selection adopts a small SQLite database, which improves the simplicity of installation and use, and facilitates later maintenance. The database mainly completes data storage and reading operations, and mainly saves data for user information and transducer test data. The database has a report export function, and the selected data can be exported in the form of an EXCEL form, which is convenient for users to search and count data.

The above-mentioned embodiments are not limitations to the present invention, and the present invention is not limited to the above-mentioned examples, and changes, modifications, additions or substitutions made by those skilled in the art within the scope of the technical solution of the present invention also belong to this invention. protection scope of the invention.

Claims (8)

1. A piezoelectric ultrasonic transducer test system is characterized in that: the ultrasonic transducer testing device comprises an upper computer (1), an ultrasonic transducer tester (2) and a tool support (3); the upper computer (1) is connected with the ultrasonic transducer tester (2); the ultrasonic transducer tester (2) is connected with the ultrasonic transducer (4) to be tested; the ultrasonic transducer tester (2) is used for carrying out parameter detection on the ultrasonic transducer (4) to be tested, and the parameter detection comprises static parameters: a resonant frequency, an anti-resonant frequency, a resonant impedance, an anti-resonant impedance; dynamic parameters: transmitting amplitude and receiving amplitude; the ultrasonic transducer (4) to be tested is arranged in a test hole of the tool bracket (3); the tool support (3) is positioned in a container for containing water;

the ultrasonic transducer tester (2) comprises a main control module; the main control module is respectively connected with the clock reset module, the power supply module and the configuration module; the main control module is connected with the communication module; one end of the communication module is connected with the touch screen, and the other end of the communication module is connected with the upper computer (1); the main control module is connected with the control circuit; one end of the control circuit is connected with the constant current source circuit, and the other end of the control circuit is connected with the tested circuit; the tested circuit is connected with the signal conditioning module; the signal conditioning module is connected with the main control module through the A/D module.

2. The piezoelectric ultrasonic transducer testing system according to claim 1, wherein: the frequency of an excitation signal output by the ultrasonic transducer tester (2) is adjustable, and the adjustable range is 1KHZ-100 MHZ; the ultrasonic transducer tester (2) is connected with the upper computer (1) in an RS232 communication mode.

3. The piezoelectric ultrasonic transducer testing system according to claim 2, wherein: the main control module is an FPGA chip with the model number of EP2C8Q208C 8N; the type of the A/D module is a high-speed A/D converter AD 9244; the model of the touch screen is an industrial serial port screen of the DC80480B070_ 03T/NW.

4. The piezoelectric ultrasonic transducer testing system according to claim 3, wherein: the tool support (3) is made of 304 stainless steel; the finish degree of a reflecting surface at the bottom of the tool support (3) is less than 3.2; the height of the tool bracket (3) is 30-50 mm.

5. The method of testing a piezoelectric ultrasonic transducer according to claim 1, wherein: the use method of the test system comprises the following steps:

A. opening the upper computer (1);

B. connecting the ultrasonic transducer tester (2) with the upper computer (1) through a serial port line;

C. putting the tool support (3) into a container containing water, putting the ultrasonic transducer (4) to be tested into a test hole of the tool support (3), and adjusting the temperature of the water in the container according to test requirements;

D. connecting the ultrasonic transducer tester (2) with the ultrasonic transducer (4) to be tested, wherein the anode and the cathode of a lead of the ultrasonic transducer (4) to be tested correspond to the signal output polarity of the ultrasonic transducer tester (2);

E. configuring a port number on the upper computer (1) and establishing the connection between the upper computer (1) and the ultrasonic transducer tester (2);

F. the selectivity can be tested in the upper computer (1), the resonance and anti-resonance frequency, the resonance, anti-resonance impedance, the transmitting amplitude and the receiving amplitude information of the ultrasonic transducer (4) to be tested are detected, the transmitting amplitude and the receiving amplitude data are processed, and accordingly, the equipment data and the qualified mark are carried out on the ultrasonic transducer (4) to be tested.

6. The method of the piezoelectric ultrasonic transducer testing system according to claim 5, wherein: the use method of the ultrasonic transducer tester (2) comprises the following steps:

I. starting up: turning on a power switch of the ultrasonic transducer tester (2), wherein a display screen of the power switch is a touch operation screen;

II, connecting: connecting the ultrasonic transducer tester (2) with the ultrasonic transducer (4) to be tested;

and III, entering a corresponding detection page in a mode of clicking a touch screen through a touch screen: three function choices of resonance and anti-resonance frequency detection, resonance impedance and anti-resonance impedance detection and transmission amplitude and reception amplitude detection are provided;

resonance and anti-resonance frequency testing: switching a test item change-over switch to one side of frequency impedance, selecting resonance and anti-resonance frequency for detection, inputting initial scanning frequency and termination scanning frequency, wherein the initial value is 500KHZ at minimum, and the termination value is 2500KHZ at maximum; setting a frequency sweep range click determination button, displaying the resonance frequency and the anti-resonance frequency of the device to be tested, and observing the waveform of frequency scanning in real time by using a click frequency curve;

v. resonant and anti-resonant impedance testing: and entering an impedance detection selection page, and selecting the resonant impedance or the anti-resonant impedance to be tested, wherein the resonant impedance detection needs to use the resonant frequency value of the device, and the anti-resonant impedance detection needs to use the anti-resonant frequency value of the device.

7. The method of the piezoelectric ultrasonic transducer testing system according to claim 6, wherein: the specific process of the resonance impedance test in the step V is as follows: selecting a resonant impedance detection option, entering a resonant impedance test page, and switching the test item switcher to the impedance frequency side at the moment, wherein the specific steps are as follows:

a. inputting the resonant frequency of the ultrasonic transducer (4) to be tested;

b. clicking an amplitude determination button to determine the amplitude under the current resonant frequency;

c. adjusting an impedance adjusting button to enable the equivalent amplitude to be equal to the confirmed amplitude in the previous step;

d. and clicking an adjustment determining button to confirm that the current equivalent amplitude adjustment is finished, and reading the resonant impedance.

8. The method of the piezoelectric ultrasonic transducer testing system according to claim 6, wherein: the main control module adopts a method of firstly frequency multiplication and then frequency division to multiply the frequency of the clock to 300M and applies a table look-up method to generate a square wave signal of 1KHz-100 MHz.

Images