MEASUREMENT OF THE DISSIPATION ASSOCIATED WITH THE ELECTROMECHANICAL COUPLING IN PIEZOELECTRIC CERAMICS
CONNECTICUT UNIV STORRS DEPT OF ELECTRICAL ENGINEERING
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An investigation was made to develop methods for precise measurements of velocity or displacement including their phase angles as well as their magnitudes and to apply these methods to extend the knowledge of the dissipative parameters of piezoelectric ceramics. Laser interferometry is a very promising new method for measuring small vibrations. In this method the motion of a small mirror attached to the vibrating body phase-modulates the light beam, and the light beam is subsequently demodulated by a photomultiplier tube. An electronic control system was developed to stabilize the interferometer against low-frequency building vibrations. In this system the mirror of the interferometer that is normally fixed is mounted on a small piezoelectric transducer. This transducer is driven by a servo amplifier in such a manner that it keeps the path length of the interfering beams constant at low frequencies. Building vibrations thus are canceled out, but the control system becomes inoperative above 1 kHz and, hence, does not interfere with the measurement of the desired vibration signals, which are in this upper frequency range. Another feedback control system was developed to stabilize the amplitude of the laser output, which was found to fluctuate as much as 10 percent. These fluctuations were reduced to about 1 percent. After suitable measurement methods had been developed, measurements were made of the electromechanical transfer ratios of a number of ceramic samples.
- Ceramics, Refractories and Glass
- Test Facilities, Equipment and Methods