Application Cases

Experiment Name: Research on Calibration Technology of Acoustic Field Characteristics of Ultrasonic Transducers Based on Hydrophone Method

Research Direction: Ultrasonic Transducers

Experimental Objective:
Ultrasonic non-destructive testing (NDT) is one of the significant techniques in the field of non-destructive testing. As a critical component in ultrasonic testing, transducers are widely used in industrial testing and medical ultrasonic imaging. Their performance directly affects the effectiveness and application scope of ultrasonic technology, particularly acoustic field characteristics, which significantly influence the detection range, defect detection rate, and accuracy of defect evaluation in ultrasonic NDT. Therefore, conducting in-depth research on accurately measuring the acoustic field characteristic parameters of ultrasonic transducers is of great value.

This study focuses on the calibration of acoustic field characteristic parameters of ultrasonic transducers using the hydrophone method, including the equipment composition and technical specifications of the calibration setup, as well as calibration methods for acoustic field parameters such as focal length, focal zone size, and beam divergence angle. Experimental measurements of acoustic field characteristic parameters are performed, and the experimental data are further discussed.

Testing Equipment:
ATA-8202 RF power amplifier, hydrophone, signal generator, oscilloscope, etc.

Experimental Procedure:

Figure: Schematic Diagram of the Ultrasonic Transducer Acoustic Field Calibration System

The ultrasonic transducer acoustic field calibration system mainly consists of an ultrasonic acoustic field scanning and positioning device, an ultrasonic pulse excitation device, and a signal acquisition device. The schematic diagram of the calibration system is shown above.

1. Installation of the Standard Hydrophone and the Ultrasonic Transducer Under Test

• The membrane at the tip of the hydrophone is extremely fragile. Therefore, the hydrophone tip must not be touched by fingers or any other objects. Gently rinse it with distilled water if necessary.

• Secure the standard hydrophone onto the clamping bracket of the five-degree-of-freedom motorized motion system, ensuring that the connecting wires do not entangle with the motion mechanism.

• Secure the ultrasonic transducer under test onto the clamping bracket of the manual five-degree-of-freedom motion system, ensuring that the connecting wires do not entangle with the motion mechanism.

• After installation, adjust the positions and orientations of the ultrasonic transducer under test and the standard hydrophone by driving the manual and motorized five-degree-of-freedom motion systems, respectively. Ensure that the surface of the ultrasonic transducer under test remains perpendicular to the hydrophone as much as possible, and that the axes of the transducer and the hydrophone are aligned along the same line at the center of the water tank.

2. System Connection and Calibration

• Connect the ultrasonic transducer under test to the power amplifier and signal generator. Set the signal generator operating frequency to the nominal frequency of the transducer (2.25 MHz) and switch it to burst mode. Set the number of pulse excitation waveform cycles to 10 to ensure the hydrophone output reaches a steady state.

• Connect the standard hydrophone to the amplifier and oscilloscope. Use the motorized five-degree-of-freedom motion system to move the hydrophone with a step distance of 0.2 mm and a speed of 10 mm/s for multi-plane scanning to obtain the acoustic field characteristic parameters.

Experimental Results:

Figure: Measurement Results of Acoustic Field Characteristic Parameters for a Focused Ultrasonic Transducer

Comparison of the actual measurement results with theoretical values shows that the measured acoustic field aligns well with the simulation results. The measured acoustic field characteristic parameters fall within a reasonable range, demonstrating that the system can accurately measure the acoustic field of the focused transducer.

Aigtek ATA-8000 Series RF Power Amplifier:

Figure: Specifications of the ATA-8000 Series RF Power Amplifier