In this paper I present an implementation of an observatory instrument, that is made for Hungarian Academy of Sciences Geodetic and Geophysical Institute and it will be installed at Széchenyi István Geophysical Observatory. It measure the telluric current, those are induced by the geomagnetic field. At the observatory two electrode pairs are situated below the ground with distances of 500 meters in North-South and East-West directions to measure these current at 2 dimension plane. The measurement has established since the foundation of the observatory (1957). The requirement of the new instrument was raised mainly due to extend the frequency range of the registrated currents, and the newer instrument allows to make a better quality of the registration.
The instrument measures the voltages between the electrodes and sends the data to a computer where the data are stored. It measures at DC-100Hz frequency range. It has two channels with the same parameters, the minimum amplitude 5μV. The measurement is made more difficult by the power network that generates noise at the measurement frequency range.