Photometric device

Claim 1

A PHOTOMETRIC DEVICE IN WHICH A FIRST RESISTIVE MEANS IS TO HAVE ITS RESISTIVE VALUE VARIED IN INVERSE PROPORTION TO A LIGHT FLUX TO BE VARIED COMPRISING A FIRST SERIES CIRCUIT INCLUDING SAID FIRST RESISTIVE MEANS, A FIRST SOURCE OF CONSTANT VOLTAGE AND A PHOTOSENSITIVE DEVICE ALL CONNECTED IN SERIES WITH ONE ANOTHER, SAID PHOTOSENSITIVE DEVICE BEING OF A TYPE WHICH MAINTAINS A CONSTANT CURRENT IN SAID FIRST CIRCUIT WITH VARIATIONS IN THE RESISTIVE VALUE OF SAID FIRST RESISTIVE MEANS AND WHICH VARIES THE CURRENT THEREIN AS A FUNCTION OF CHANGES IN LIGHT FLUX FALLING ON SAID PHOTOSENSITIVE DEVICE, A SECOND SERIES CIRCUIT INCLUDING SECOND AND THIRD RESISTIVE MEANS AND A SECOND SOURCE OF SUBSTANTIALLY CONSTANT VOLTAGE ALL CONNECTED IN SERIES WITH ONE ANOTHER, ONE OF SAID SECOND AND THIRD RESISTIVE MEANS BEING VARIABLE, SAID FIRST AND SECOND CIRCUITS BEING CONNECTED TOGETHER AT ONLY ONE POINT; A HIGH IMPEDANCE MEASURING DEVICE CONNECTED BETWEEN A LOCATION IN EACH OF SAID CIRCUITS REMOTE FROM SAID POINT OF CONNECTION, ONE OF SAID VARIABLE RESISIVE MEANS OF EACH OF SAID CIRCUITS LYING BETWEEN EACH SAID LOCATION AND SAID POINT OF CONNECTION, SAID LOCATIONS HAVING THE SAME POLARITIES RELATIVE TO SAID POINT OF CONNECTION; SAID SOURCES OF VOLTAGE AND SAID RESISTIVE MEANS BEING SUCH THAT THE TOTAL VOLTAGE BETWEEN SAID LOCATIONS MAY BE MADE EQUAL TO ZERO; AND MEANS FOR ADJUSTING AT LEAST SAID FIRST RESISTIVE MEANS TO ADJUST SAID TOTAL VOLTAGE TO ZERO IN THE PRESENCE OF THE LIGHT FLUX TO BE MEASURED WHEREBY THE VALUE OF SAID FIRST RESISTIVE MEANS VARIES IN INVERSE PROPORTION TO THE LIGHT FLUX TO BE MEASURED.