Characterization of transducers and resonators under high drive levels

Abstract

-In many applications, piezoelectric transducers are driven at AC voltage levels well beyond the level for which the material was nominally characterized.In this paper we describe an experimental setup that allows for the determination of the main transducer or resonator properties under large AC drive. A sinusoidal voltage from a waveform generator is amplified and applied across the transducer/resonator in series with a known high power resistor. The amplitude of applied voltage and the amplitude and the relative phase of the current through the resistor are monitored on a digital scope. The frequency of the applied signal is swept through resonance and the voltage/current signals are recorded.After corrections for the series resistance and parasitic elements the technique allows for the determination of the complex impedance spectra of the sample as a function of frequency. In addition, access to the current signal allows for the direct investigation of non-linear effects through the application of Fourier transform techniques on the current signal. Our results indicate that care is required when interpreting impedance data at high drive level due to the frequency dependence of the dissipated power. Although the transducer/resonator at a single frequency and after many cycles may reach thermal equilibrium, the spectra as a whole cannot be considered an isothermal measurement due to the temperature change with frequency. Methods to correct for this effect will be discussed. Results determined from resonators of both soft and hard PZT and a ultrasonic horn transducer are presented.

Frequency dependence of piezoelectric vibration velocity

“…(7). This 3D description is used because temperature rise is determined by both the heat generation and dissipation of the vibrating actuator [3,4,10,[23][24][25][26][27]. The heat dissipation is proportional to the surface area (where heat dissipates) to vol- Fig.…”

Ultrasonic Thruster

“…While temperature studies on PZT have been adequately described and investigated in the literature (Duck, Starritt, ter Haar, & Lunt, 1989;Sherrit et al, 2001), we are not aware of any work that makes a direct connection between transducer temperature rise and the propulsive thrust generated. As the UST is an underwater propulsor, knowledge of the conditions leading it to become a thermal source is important in many applications.…”

“…where x p (m) is the thickness of the transducer, k p (W/mC) is the thermal conductivity of the transducer, A p (m 2 ) is the surface area of the transducer, and T p (C) is the temperature at the interface between the transducer and epoxy layer (Sherrit, et al, 2001). Q p (W) is the average heat transfer rate of the piezoelectric material, which is also the average power dissipation, given by 2 2t a n…”

Quality factor concept in piezoceramic transformer performance description

“…8 for a Rosen-type PT, that demonstrates the described approach of building up the practicalQ(f r ) relationship when two kinds of the dependencesQ(t) and f r (t) are preliminarily established. According to (12)- (20), the frequency of maximum input PT admittance (f m ) generally does not coincide with the PT resonance frequency (f r ) of maximum input and output power, efficiency, transformation ratio and input conductance, especially in the range of the load parameter t ∈ (0.1 . .…”