Geophysical Company of Norway A.s.

Eigil Larsen

Clive T Snook

Eldar K Lien

An arrangement in a piezoelectric hydrophone that is provided with a protective outer housing enveloping a waterproof closed casing (2). Said casing is provided with two mutually opposed and parallel diaphragm wafers (3) on the insides of which piezoelectric crystals (4) being metal coated on their outsides are respectively attached. A connecting wire is extended from said case through its hollow central portion (6). Said central portion (6) is formed by at least two ceramic elements (7) joined along a plane parallel with the diaphragm wafers and provided with a metalization (11) in the mutual contact areas (9, 10). In the cavities (12) respectively of the two elements (7) stiffening ceramic disks (8) are provided and attached to the elements (7) by the aid of a matching projection (13). The inward facing poles of the piezoelectric crystals are conductively connected with the metalization in the contact plane of the elements, and an additional wire (5) is provided from the metalization (11) on the outside. The poles facing outward of said crystals are connected via said diaphragm wafers (3) on the outside of the casing (2). The ceramic material used is Al.sub.2 O.sub.3 having a degree of purity of more than 85%.

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Horten, Norway

Eigil Larsen