Abstract
A new ferroelectric sensor for measuring the particle motion in hydroacoustic fields has been developed. The sensor is a capacitor constructed by adding conducting end plates to single crystals or polymer composites of antimony sulfur iodide (SbSI). The device is operated above the Curie point of about 20 °C. The heating is accomplished through the hysteresis cycle driven by a Sawyer-Tower-type bridge. In the temperature region slightly above the Curie point, both the real part ε′ and the imaginary part ε″ of the dielectric permittivity have a large negative slope as a function of temperature. The negative slope in ε″ causes the Temperature Autostabiling feature of the Nonlinear Delectric ELement (TANDEL). Cooling the sensor by a fluid flow changes the temperature of the sensor, and consequently ε′ and ε″. The change of ε′ unbalances the bridge, producing a detectable signal. The output for steady flow shows the characteristic exponential dependence on fluid speed. The sensor displays directional sensitivity. The response to low-frequency acoustic fields is discussed and related to the heat transfer properties of horizontal cylinders. [Work supported by the ONR.]
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