The use of air condensers as high-voltage standards

The paper discusses the essentials of correct screening for high-voltage air condensers in order to maintain a high degree of purity and constancy of capacitance with voltage. Tests are described showing the effect of dust and humidity on the purity of an air condenser. Details of the design of three air condensers, the largest working at voltages up to 300 kV, are then given. The precautions necessary in obtaining an accuracy of the order of 1 part in 104 in the calculated capacitance of one of these condensers are dealt with and means are described for measuring the capacitance of air condensers accurately. Test-results are given which show the phase error of this condenser to be less than 0.00001 up to its rated voltasge. Finally, the outstanding advantages of air condensers as high-voltage standards are outlined.