Process and device for measuring an alternating electric current with temperature compensation

A device for measuring an alternating electric current, comprising:

• a plurality of injection devices for injecting a linearly polarized measuring light into a sensor device subjected to a magnetic field generated by the alternating electric current, the linearly polarized measuring light having a polarization plane which is rotated as a function of the alternating electric current;
• an analyzer for splitting the linearly polarized measuring light into two linearly polarized component light signals having different corresponding polarization planes, the linearly polarized measured light being split after passing at least once through the sensor device;
• optoelectric converters for converting each of the two linearly polarized component light signals into a respective electric intensity signal;
• normalizing devices for forming respective normalized intensity signals as a function of the respective intensity signals, the normalized intensity signals corresponding to a quotient of an alternating signal component and a direct signal component of the respective intensity signal;
• analyzing devices for deriving a measuring signal for the alternating electric current as a function of the normalized intensity signals substantially in accordance with the formula:
• S=(2.multidot.S1.multidot.S2)/((S2-S1)+K.multidot.(S1+S2)),
• wherein K is a real correction factor and wherein:
• cos(2.theta.+2.eta.)=-2/(3K), and sin(2.theta.-2.eta.)=1,
• where:
• .eta. is an injection angle of the plane of polarization of the measuring light injected into the sensor device with respect to a natural axis of a linear birefringence in the sensor device, and
• .theta. is an exit angle between the natural axis of the linear birefringence and a natural axis of the analyzer.