抄録
Optical voltage and current measurement generally necessitates the compensation of light beam intensity variation which occurs in the optical measuring system, because it is possible the light beam intensity variation may give rise to a measuring error. Therefore, such compensation methods as dividing the A C component by the D C component of the light beam intensity are usefully introduced in optical A C voltage and current measurement, but these methods are not useful exactly for the optical measurement of the quantities including D C components.
This paper deals with a new useful compensation method for light beam intensity variation in the optical D C current measurement. Linearly polarized light beam passes through two kinds of Faraday sensors, in which one detects D C magnetic field caused by D C current and the other detects externally applied constant A C magnetic field. Then, the compensation of the light beam intensity variation is carried out by measuring the D C and A C components of the beam. The principle of the compensation method using the A C component is described in the paper. Experimental results of this method using flint glass as the Faraday effect cells are reported and it is clarified that this method can decrease the measuring error of the modulation depth for D C current and compensate light beam intensity variation validly.
