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7 - Galitzine


Galitzine horizontal

Galitzine vertical

Made in 1910 in Saint-Petersbourg. In use in Strasbourg from 1910 to 1975.
Two instruments of similar design: the first is for recording a horizontal component and the second a vertical component:

  • an electromagnetic seismometer: a coil oscillates in a magnetic field and creates a measurable electric current by induction
  • damping by Foucault current
  • horizontal: mass 7kg (15lb); period 12s
  • vertical: mass 10kg (22lb); period 24s
  • optical recording by means of a galvanometer mirror with a mobile frame.

This is the first electromagnetic instrument developed for recording earthquakes.

The two Galitzine seismometers represent a major technological breakthrough. Made from 1910 onwards, they are the first to use the principles of electromagnetism.They are "simple" pendulum, so called because they are designed to record a single component which may be horizontal or vertical depending on the apparatus in question. The innovation resides in the coil placed at the far end of the pendulum's rod. This coil oscillates in a magnetic field and by its displacement creates an electric induction current. A copper plate, fixed on the same rod as the coil, oscillates in the field of a second magnet and allows for damping by Foucault current. The current is transmitted to a galvanometer equipped with a mobile frame and a mirror. A beam of light shed on the mirror records the deflected beam on photopaper. Two types of amplification take place: electromagnetic amplification - the galvanometer mirror turns much more than the pendulum oscillates - and optical amplification due to the distance between the photographic plate and the mirror.

Galitzine horizontal

The advantages of this process can be easily seen. No more huge masses, no more difficult settings... Galitzine instruments are the beginning of the developments which led to modern equipment, made up, for the most part, of instruments which combine electromagnetism (a small mass and a magnet) and electronics.