Hungarian Academy of Sciences Boltek EFM 100. Potential gradient (PG) is measured using a BOLTEK EFM 100 Atmospheric Electric Field Monitor. It is mounted on a 3m metal pole surrounded by trees at a distance of ~ 15-30 m. Resolution of measured PG values: 10 V/m. The measurement is calibrated by the BOLTEK company. The official user manual suggests a calibration method aided by a second field mill, which has not been performed yet. Elevation of the site is 153m above mean sea level. The data is contains 1 second and 1 minute averages.

The instrument is located at MTA CSFK GGI Széchenyi István Geophysical Observatory (47.63'N, 16.72'E).