Sensitivity Considerations for PVDF Hydrophones Using the Spot-Poled Membrane Design

Abstruct-me receiving sensitivities of piezoelectric polymer polyvinylidene fluoride (PVDF) hydrophones constructed using the spot-poled membrane design are studied. Formation of deposited leads and the effect of different lead geometries on sensitivity are discussed, and a comparison between voltage and charge amplification techniques is made. Sensitivity variations of withii f 1 dB from 1-10 MHz were achievable for hydrophones having active element diameters of from 0.3-1.0 mm. Depending on the element size and amplifier type and confiiration, the sensitivities ranged from approximately -234 to -268 dB re 1VjbPa. In addition, equivalent noise pressure levels (l-Hz band) of from 109-131 dB re I pPa were measured. 'Ihe resulting signal-to-noise (SIN) ratios for these probes were found t o be within the limits specified by the American Institute of Ultrasound in Medicine and National Electrical Manufacturers Association for hydrophone measurements of pulseecho diagnostic devices.