Instrument for measuring temperature of extended surfaces

Claim 1

IN AN INSTRUMENT FOR DETERMINATING THE TEMPERATURE OF A MATERIAL TO BE MEASURED AS COMPARED TO THE TEMPERATURE OF AN EXTENDED REFERENCE PLATE WHICH HAS LINE DIMENSIONS LARGE IN COMPARISON TO THE SPACING BETWEEN THE PLATE AND THE MATERIAL TO BE MEASURED, THE IMPROVEMENT WHICH COMPRISES: (A) A REFERENCE PLATE HAVING DIMENSIONS AT LEAST AN ORDER OF MAGNITUDE GREATER THAN THE SPACING FROM THE MATERIAL THE TEMPERATURE OF WHICH IS TO BE MEASURED, (B) HEATING MEANS FOR MAINTAINING THE SURFACE OF THE REFERENCE PLATE AT A PREDETERMINED TEMPERATURE, (C) TEMPERATURE SENSING MEANS EMBEDDED IN THE SURFACE OF THE REFERENCE PLATE, SAID SENSING MEANS CONTROLLING THE OPERATION OF THE HEATING MEANS, (D) A DIFFERENTIAL RADIATION DETECTOR HAVING ELEMENTS EXPOSED TO RADIATION AND REFERENCE ELEMENTS SHIELDED THEREFROM, SAID DIFFERENTIAL DETECTOR BEING SUBSTANTIALLY CENTRICALLY LOCATED IN THE REFERENCE PLATE, (E) MEANS FOR MAINTAINING THE REFERENCE ELEMENTS OF THE DIFFERENTIAL DETECTOR AT REFERENCE PLATE SURFACE TEMPERATURE WHEREBY THE ELEMENTS OF THE DETECTOR RECEIVING RADIATION FROM THE MATERIAL THE TEMPERATURE OF WHICH IS TO BE MEASURED PRODUCED A DIFFERENTIAL SIGNAL WHICH IS ZERO WHEN THE TEMPERATURE OF THE SURFACE TO BE MEASURED IS IN THE SAME AS THAT OF THE SURFACE OF THE REFERENCE PLATE, AND (F) ELECTRONIC PROCESSING MEANS FOR THE DIFFERENTIAL DETECTOR OUTPUT PRODUCING A SIGNAL WHICH IS A FUNCTION OF TEMPERATURE DIFFERENCE BETWEEN THE REFERENCE PLATE SURFACE AND THE SURFACE TO BE MEASUREED.