An antenna electrometer system for atmospheric electrical measurements

A +/-300 V dynamic range, battery-powered, and inexpensive electrometer system is described that has been used with passive horizontal wire antennas to measure the atmospheric electric potential at I and 2 m above the earth's surface. Input currents drawn by the electrometer circuit are of order femtoamperes, and a guard drive output is provided to minimize leakage. The implementation of the passive wire antenna is described, using rigorous insulation and signal guarding, together with results obtained in fair weather conditions. Linearity of the portable electrometer over the input range is demonstrated to be comparable with a commercial laboratory electrometer, and the antenna potential can be determined to within a few volts in the fair weather electric field. Several such portable systems can be cheaply combined, sharing a common high tension supply, to measure the profile of the atmospheric electrical potential above the surface, at a remote site, Damage to the electrometer sustained in electrical storms can be cheaply repaired. (C) 1997 American Institute of Physics.