The sparkless sphere gap voltmeter

Sphere gaps may be used for measuring very high voltages by holding them at a separation greater than spark-over distance, and measuring the Force between them. The voltage may then be calculated easily and accurately from well known electrostatic principles. Among the advantages of this type of measurement over the conventional spark-over methods are: no corrections are necessary for air temperature, humidity, and pressure; effective voltage values are given; measurements are not erratic; and numerous difficulties in taking measurements are avoided.