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About IIG Observatory Instruments and Facilities


Instrument Details

Make: Lviv Centre of Institute of Space Research, Ukraine
Model: LEMI-30i
Locations: Shillong, Jaipur, Silchar, Maitri, Bharati

Specifications: Each of three LEMI-30i Induction-coil sensors has following parameters:

The complete set of the magnetometer consists of three LEMI-30i sensors, one communication unit (CAM Unit) and accessories (cables, GPS antenna and PC software) and portable PC. All three LEMI 30i sensors have similar construction and characteristics.
Each of LEMI-30i sensors consists of the Induction-coil and two PCB fixed inside the protective housing. The front panel of the sensor has the connector for cable coupling. Induction coil sensor consists of mu-metal sensor core SC, main winding W m, additional winding W c and two feedback windings W f1 and W f2.
Sensor core is made of a number of insulated tapes of high permeability amorphous alloy, and is fixed inside the tubular housing on which all windings are wound.

Induction coil, or search coil, magnetometers measure changes in magnetic field. Faraday's law of inductance describes the relationship of induced voltage to a changing magnetic field, and is the operating principle of this design of magnetometer. Essentially, the magnetometer consists of a coil with a very large number of turns of wire wrapped around a high permeability core. The relationship between the measured signal ( V), the number of turns ( n), the area of the coil ( A), the relative permeability of the core material ( µ r) and the changing magnetic field ( B) can be expressed as: The core acts as a magnetic field concentrator, increasing the density of the magnetic field inside the coil, and so increasing the sensitivity. A feedback winding is also wound around the core to flatten the frequency response of the magnetometer.

  • Schumann Resonance
  • Geomagnetic Pulsations
  • Earthquake precursors in ULF/ELF range

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