Geophone with stationary coil and moving permanent magnet - mounted on spring bushes and polarisable according to direction of vibrations expected

摘要

Conventional geophones, i.e. seismometers for geophysical research, have a fixed permanent magnet inside a pick-up coil which is vibrated by the seismic shock. The movable coil can produce harmonic distortion and its connections can be damaged by excessive vibrations. The present geophone has a movable, hollow, cylindrical, permanent magnet (116), mounted on spring bushes to the outer housing (114) of the geophone. The pick-up coil (110) passes through the hollow body of the magnet in a cylindrical housing (112). The magnetic body (116) may be radially or axially polarised, dependent on the direction of the vibrations it is required to detect. The present geophone is more robust than conventional geophones and less likely to produce harmonic distortion.