Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1986-05-22
1987-10-06
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250225, 324 96, 356368, G01D 534, G01R 3100, G02F 101, G01J 400
Patent
active
046984976
ABSTRACT:
A drift free magneto-optic current transformer for measuring an electric current which may include a d-c component in which two orthogonally polarized light beams are passed through a magneto-optic element operating as a Faraday rotator to rotate the beams through an angle dependent upon the magnitude of the d-c current. An analyzer, oriented with two orthogonal polarization axes set at +45 degrees and -45 degrees with respect to the plane of polarization of the first input light beam and at -45 degrees and +45 degrees with respect to the plane of polarization of the second input light beam, splits each emerging light beam into two output light beams which are converted into a.sub.1 and b.sub.1, and a.sub.2 and b.sub.2 electrical signals in response to the first and second input light beams respectively. By maintaining the signal (a+b).sub.1 equal to (a+b).sub.2, and by maintaining (a-b).sub.1 +(a-b).sub.2 equal to zero, an output signal (a-b).sub.1 -(a-b).sub.2 proportional to the magnitude of the d-c current, and free from drift due to changes in the attenuation characteristics of the optical components, is obtained without the necessity of dividing by a variable.
REFERENCES:
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patent: 3753101 (1973-08-01), Aumont
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patent: 4554449 (1985-11-01), Taniuchi et al.
patent: 4564754 (1986-01-01), Sato et al.
patent: 4613811 (1986-09-01), Vaerewyck et al.
Asars Juris A.
Miller Robert C.
Abeles Daniel C.
Ruoff J. L.
Westin Edward P.
Westinghouse Electric Corp.
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