An Absolute Method of Measuring High Frequency Currents

Abstract

UNTIL recently the measurement of currents at radio-frequencies has depended on the assumption that the instruments used did not alter their calibration with frequency, and every endeavour was made to satisfy this condition. The method largely adopted comprised the use of sufficiently thin conductors so that freedom from skin effect could be obtained. While this naturally limited the magnitude of the currents which could be employed satisfactorily, transformer and condenser methods have been used by D. W. Dye and P. R. Coursey respectively at medium radio-frequencies, for the conversion of large currents into those which could more conveniently be measured directly. More recently, E. B. Moullin has developed an instrument the operation of which depends upon the attraction of two parallel wires carrying the same current. While this instrument would appear to be satisfactory as an absolute method of measurement, it has been considered desirable to develop another method based upon a different principle in order to place the very important subject of radio-frequency current measurement on secure foundations.