| 摘要 |
Provided is an electric current measuring instrument wherein compensation for the ratio error versus temperature characteristics of optical fibers and Faraday rotators for a sensor can be made by an optical system of an electric current instrument and wherein the fluctuation range of ratio errors in outputs can be brought within a range of ±0.5%. The fluctuation range of ratio errors in measured values of electric currents outputted by a signal processing circuit is set within a range of ±0.5% over a temperature range of -20OC or more to 80OC or less by means of the following: An electric measuring instrument is constructed in such a way as to include a signal processing circuit equipped with at least a polarized light separation unit, Faraday rotators, a light source, a photoelectric conversion element, and optical fibers for a sensor. The optical fibers for the sensor are placed around the periphery of an electrical conductor through which electric current to be measured flows. Furthermore, the rotation angle of each Faraday rotator at the time when the magnetism of each Faraday rotator is saturated is set to 22.5O + aO at a temperature of 23OC, thereby changing the rotation angle of each Faraday rotator by aO from 22.5O. |
