The present invention relates to a hydrophone specifically designed for use in high pressure shock wave fields, comprising a thin piezoelectric polymer film secured to a rigid hoop structure, having a centrally located active element and two conducting leads extending from the active element on each side of the film. Under the action of high pressure shock waves, the conductive material which makes up the active area electrode and the conductive leads is slowly removed, altering the hydrophone's sensitivity and eventually rendering it unusable. The present invention provides an improved design for a hydrophone which monitors the loss of electrode and lead integrity due to shock wave action so that the hydrophone may be replaced before it produces invalid readings. The leads on each side of the centrally located active element are electrically switched to measure the resistance between the leads and the central portion. In another embodiment, the film may be a disposable item allowing for rapid replacement once damaged.
An acoustic device, such as a membrane hydrophone, includes a support structure and an outer membrane that suspends a transducer membrane within the interior of the support structure. The transducer membrane is selected for its acoustic and piezoelectric properties and is preferably a polymer such as P(VDF-TrFE). The outer suspension membrane is selected primarily for its mechanical properties. Portions of the suspension membrane may be removed in order to reduce mechanical drag encountered during movement of the device in a liquid. The transducer membrane includes at least one active area that is poled to provide a piezoelectrically strong region. Electrical charge generated at the active area is amplified at a preamp for transmission to remote equipment.
An omnidirectional ultrasonic microprobe hydrophone is disclosed. Applicans include underwater mine detection, explosive shock testing, high wave number measurements, medical imaging, and therapeutic systems. The apparatus includes at least two lead zirconate titanate (PZT) pressure sensing elements having a plurality of columnar voids formed therein. The pressure sensing elements are deposited on a metallic or nonmetallic substrate which provides mechanical support for the microprobe hydrophone. Electrical connection to the pressure sensing elements is made by deposition of conductors and insulators on the substrate material. Wire bonds are used to attach wire leads for connection to a supporting structure containing a preamplifier. Line arrays and planar arrays of microprobe hydrophone elements are also disclosed.
