A geophone with a magnet and a coil concentrically arranged around a central pole

摘要

A vibration transducer such as a geophone, comprising a central pole piece ( 110 ) with a magnet ( 112 ) and coil ( 118 ) concentrically arranged around it. The position of the magnet ( 112 ) is fixed relative to the pole piece ( 110 ) and the coil ( 118 ) is movable relative to the magnet ( 112 ). A method of manufacturing a vibration transducer is characterised in that a bobbin carrying the coils is formed from a substantially tubular body which is positioned on a mandrel and at least one coil is wound around its outer surface, the mandrel being removed from the bobbin when the coil is complete. Another method is characterised in that the coil is formed separately and the bobbin is formed from a substantially tubular body which is positioned inside the coil and expanded to contact the coil when in position.