Patent ID: 8957667
Filing Date: 2015-02-17
Classification: G01R

Abstract:
1. An electric current measuring apparatus comprising: a signal processing circuit which includes at least an optical fiber for a sensor, a polarization separating unit, a Faraday rotator, a light source, and a photoelectric conversion element, wherein the optical fiber for a sensor is provided around the periphery of an electrical conductor through which an electric current to be measured flows, and has one end at which linearly polarized light is incident and the other end at which the incident linearly polarized light is reflected, the polarization separating unit is provided at one end of the optical fiber for a sensor, the Faraday rotator is disposed between one end of the optical fiber for a sensor and the polarization separating unit, and the Faraday rotation angle of the Faraday rotator at the time of magnetic saturation is set to degrees of 22.5°+α° at a temperature of 23° C., a curve of temperature characteristics of a ratio error in a measurement value of an electric current to be measured, output from the signal processing circuit is shifted to a high-temperature side by adjusting the Faraday rotation angle, such that the fluctuation range of the ratio error in the measured value of a measured electric current output from the signal processing circuit is set within a range of ±0.5%, and a temperature range, in which the fluctuation range is set within a range of ±0.5%, is 100 degrees in the Celsius scale.