D.c. measuring device using hall plates connected in feedback relationship and having a common control source

Claim 1

A DIRECT-CURRENT MEASURING DEVICE FOR USE WITH A CONDUCTOR TRAVERSED BY THE DIRECT CURRENT TO BE MEASURED, COMPRISING HALL VOLTAGE GENERATOR MEANS HAVING MAGNETIZABLE CORE STRUCTURE TO BE INDUCTIVELY LINKED WITH THE CONDUCTOR AND HAVING FIRST HALL PLATE MEANS TRAVERSED BY MAGNETIC FLUX OF SAID CORE STRUCTURE DUE TO CURRENT FLOWING IN THE CONDUCTOR, SAID HALL PLATE MEANS HAVING CONTROLCURRENT SUPPLY TERMINALS AND HALL ELECTRODES; A HALL-VOLTAGE MODULATOR, HAVING MAGNET WINGING MEANS AND SECOND HALL PLATE MEANS TRAVERSED BY MAGNETIC FLUX EXCITED BY SAID WINDING MEANS, SAID SECOND HALL PLATE MEANS HAVING CURRENT-SUPPLY TERMINALS AND HALL LECTODES; ALTERNATINGCURRENT SUPPLY MEANS COMMON TO SAID TWO HALL PLATE MEANS AND CONNECTED TO SAID TERMINALS OF SAID RESPECTIVE HALL PLATE MEANS, CIRCUIT MEANS CONNECTING THE HALL ELECTRODES OF SAID FIRST AND SECOND HALL PLATES IN DIFFERENTIAL RELATION AND HAVING OUTPUT LEADS, AMPLIFIER MEANS HAVING AN INPUT CONNECTED TO SAID OUTPUT LEADS AND AN OUTPUT CIRCUIT CONNECTED TO SAID WINDING MEANS FOR CONSTRATINING THE HALL VOLTAGE OF THE SECOND HALL PLATE TOWARD THE HALL VOLTAGE OF THE FIRST PLATE, AND METER MEANS FOR MEASURING THE OUTPUT OF SAID AMPLIFIER MEANS.