New instruments for recording lightning currents

IN the early days of lightning investigations surge voltages on transmission lines were measured by a relatively crude device consisting of a number of parallel gaps with different spacings. The maximum gap broken down, which was indicated by markings on a thin piece of paper placed within the gap, was a measure of the voltage. Peters,¹ by applying the phenomenon of Lichtenberg figures to photographic films, then developed the instrument called the klydonograph. Much information concerning the magnitude and frequency of voltage surges on systems was obtained with this instrument. At about this time the cathode-ray oscillograph was just emerging from its laboratory stage of development and several investigating groups adapted it to field work. A number of records were obtained with this device which showed the rate of rise of the voltage wave, its crest, and a limited amount of information regarding its tail. However, the quantity of data secured by this means was quite small, largely because of the initial cost of the instrument and the necessity of constant attendance for operation and maintenance.