| Abstract: | Optical voltage and current measurement generally necessitates the compensation of light intensity variation which occurs in the optical measuring system, because it is possible the light intensity variation may give rise to a measuring error. Therefore, such compensation methods as dividing the ac component by the dc component of the light intensity are usefully introduced in optical ac voltage and current measurement, but those methods are not useful exactly for the optical measurement of the quantities including dc components. This paper deals with a new useful compensation method for light intensity variation in the optical dc current measurement. Linearly polarized light passes through two kinds of Faraday sensors, in which one detects dc magnetic field caused by dc current and the other detects externally applied constant ac magnetic field. Then, the compensation of the light intensity variation is carried out by measuring the dc and ac components of the beam. The principle of the compensation method using the ac 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 dc current and compensate light intensity variation validity. |
