Magnetic Calibration and Test Laboratory

The magnetic calibration and test laboratory of the Nurmijärvi Geophysical Observatory services aviation and space industry as well as manufacturers and users of ground based magnetic instruments.

We make magnetic test measurment and calibrations in the following fields:

    * Compass swing base measurements at airfields
    * Calibration of three component magnetometers
    * Sight compass calibrations

Compass calibration

The calibration of a sight compass is performed in the absolute house of the observatory on the same pillar where also the absolute values of the magnetic field (e.g. declination) are measured. A non-magnetic Askania circle base is used to rotate the compass and to read the rotation angles. A fluxgate magnetometer in the variation house records the variation of the declination during the compass calibration.

Compass Swing Base Measurement

Airplanes need to check their magnetic direction sensing elements: a flux valve or a magnetic compass. Compass swing bases at airfields serve for this task. The compass swing base need to be magnetically sufficiently clean and the direction of the magnetic field at the base need to be known.

The Nurmijärvi magnetic calibration and test laboratory has equipment and knowledge to make these measurements at airfields. A usual procedure is to start the research with a regular grid of total field measurements with a proton magnetometer. The geographic azimuth is measured with two GPS satellite receivers and the magnetic declination with two DI-theodolites.

Calibration of Three-Component Magnetometers

In the magnetic calibration and test laboratory several parameters of a magnetometer can be measured:

  1. Transformation coefficients of the sensors; analog [nT/mV] or digital [nT/nT] in the temperature range -30 ... +60 °C
  2. Angles between the three measuring components (-30...+60 °C)
  3. Angles between the three measuring components and the three magnetic directions of the coil system
  4. Optical orientation of two mechanical exes of the sensor
  5. Offsets of the measuring components
  6. Noise of the measuring components