Automatic ultrasonic measuring system using phase-sensitive detection

A new ultrasonic measuring system is developed that enables us to measure the changes in the sound velocity and attenuation in MHz frequency range simultaneously and automatically. The system utilizes a gated amplifier and a phase-sensitive detector (PSD) and is controlled by a personal computer. The unique feature of the system lies in the PSD with two double-balanced mixers that enables us to obtain simultaneously the sine and cosine components of the ultrasonic signal. The phase and amplitude of the signal are calculated from them by the personal computer and are then converted to changes in the velocity and attenuation, respectively. The performance of the PSD is tested. The system is suitable for measurements at low temperatures. The temperature dependences of the velocity and attenuation in ionic crystals are measured with this system.