Apparatus for measuring the thickness of nonmagnetic coatings on magnetic material

Claim 1

APPARATUS FOR MEASURING THE THICKNESS OF A NONMAGNETIC COATING APPLIED TO A MOVING STRIP OF MAGNETIC MATERIAL, WHICH APPARATUS COMPRISES A ROLL AT THE ENTRY END OF THE COATING APPARATUS OVER WHICH THE STRIP PASSES, A FIRST MAGNETIC HEAD ADJACENT SAID ROLL ADAPTED TO CONTACT THE UNCOATED STRIP ON THE SIDE OPPOSITE SAID ROLL, A ROLL AT THE EXIT END OF THE COATING APPARATUS OVER WHICH THE COATED STRIP PASSES, A SECOND MAGNETIC HEAD ADJACENT SAID SECOND ROLL ADAPTED TO CONTACT THE COATED STRIP ON THE SIDE OPPOSITE SAID SECOND ROLL, EACH OF SAID MAGNETIC HEADS INCLUDING A COIL, SAID COILS BEING CONNECTED IN A BRIDGE CIRCUIT WITH THE FIRST AND SECOND COILS BEING CONNECTED TO EACH OTHER, A THIRD COIL IN SAID BRIDGE CIRCUIT, A FOURTH COIL IN SAID BRIDGE CIRCUIT, SAID THIRD AND FOURTH COILS BEING CONNECTED TO EACH OTHER AND TO SAID FIRST AND SECOND COILS RESPECTIVELY, A PAIR OF LEAD WIRES ONE CONNECTED TO THE BRIDGE CIRCUIT BETWEEN THE FIRST AND SECOND COILS AND THE OTHER CONNECTED TO THE BRIDGE CIRCUIT BETWEEN THE THIRD AND FOURTH COILS, SAID LEAD WIRES BEING ADAPTED TO BE CONNECTED TO AN A. C. POWER SOURCE, A SECOND PAIR OF WIRES ONE CONNECTED BETWEEN THE FIRST AND THIRD COILS AND THE OTHER CONNECTED BETWEEN THE SECOND AND FOURTH COILS, AND MEANS FOR MEASURING THE POTENTIAL BETWEEN THE SECOND PAIR OF WIRES.