MAGNETIC OPTICAL METER OF PERMANENT MAGNETIC FIELDS AND DIRECT CURRENTS Russian patent published in 1995 - IPC

FIELD: instruments. SUBSTANCE: device uses Faraday's effect in light-sensitive magnetic film 4 having surface anisotropy. Degree of magnetization of this magnetic film depends on external magnetic fields. Film 4 is positioned on optical contact surface of hypotenuse of prism 3. Polarized light from light-emitting diode 1 is modulated in the film according to its degree of magnetization. Beams with orthogonal polarization are separated by analyzer 5 and are detected by photo diodes 6 and 7 which are connected to differential amplifier 8. Signal from output of amplifier 8 is processed in two parallel channels. first channel has low-pass filter 9 and comparator 12 which generates control signal according to sign of constant constituent of differential detected signal. second channel has high- pass filter 10, synchronization detector 11, comparator 13 which generates control signal according to sign of second harmonic of signal detected in synchronism. signals from both channels are received at input of commutator 15 which is controlled by zero detector 14. output of commutator is connected to current amplifier 16 which supplies coil 17 which serves for compensation of external magnetic fields. Effect of coercion is eliminated and possibility to operate using second harmonic of magnetizing current is provided by means of second coil 18 which is connected to high- frequency signal oscillator 19. Measured value is judged by level of current running through coil 17. EFFECT: measuring magnetic fields and currents of power supply units. 1 dwg