ANORDNING FOR AKUSTISK DETEKTERING

摘要

An improved acoustic emission transducer and transmission system for the on-line monitoring of acoustic signals generated by a metal when under mechanical stress. The transducer structure includes a tubular housing having a continuous side wall, a bottom wall and an open top. A piezoceramic element is fastened to the bottom of the housing by means of a conductive high temperature adhesive. A positive electrode is fixed to the piezoceramic element by the adhesive and both the piezoceramic element and the positive electrode are cushioned and insulated from the side wall of the housing by means of an inner tubular housing of high temperature insulating material. The inner housing assembly is sealed to enclose the piezoceramic element, adhesive and electrode - the sealant preventing moisture from penetrating the assembly and shorting the crystal. The upper end of the positive electrode passes through the sealant and is connected to an electrical cable which transmits any signal picked up by the transducer to a remote location. The cable is attached directly to a transformer which is used to couple maximum power from the transducer to an output transmission line. The transformer is selected to match the impedance of the transducer to the transmission line.