Design and fabrication of an electrometer for the measurement of atmospheric potential

Author(s): S.Manu, C.Panneerselvam, K.U.Nair, S.Gurubaran

The vertical atmospheric electric field may be sensed by using a passive antenna, which is charged slowly by exchanging the charges in the atmosphere. The potential of the atmosphere is obtained by the measurement of potential difference between the antenna and earth’s surface, which is same as the atmospheric potential. In case of a passive antenna at 1m above the surface, the voltmeter system attached with the antenna system and it is operated over a typical input range of ± 500V. This voltage is generated by a floating voltage generator. The input bias current used in this systemis of the order of nearly 10-14A with an input resistance of ~1015 Ù. This combination must be considered in this circuit is to provide an appreciably higher resistance than atmospheric resistance. In this passive antenna system a high voltage guard is also desirable. Adirect method for measuring the atmospheric electric field is used by Electric FieldMill (EFM -100) and FieldMill. The FieldMill needs 230 VAC for running the motor, regular maintenance is required. The above instruments coast high and cannot be used during severe weather condition like high wind speed, rain, lightning snowfall and drifting sand. The passive antenna can be operated any meteorological conditions with 24V battery-powered in any remote place withminimummaintenance. Damages to the electrometer due to severe electrical storms can be cheaply repaired.

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