D. c. ammeter calibrator utilizing feedback control and regulation of calibrating current

Claim 1

A SELF-BALANCING SYSTEM FOR MAINTAINING A CONSTANT CURRENT OUTPUT FROM A D.-C. CALIBRATOR COMPRISING, MEANS DEVELOPING A D.-C. POTENTIAL DIRECTLY PROPORTIONAL TO THE CURRENT OUTPUT FROM THE D.-C. CALIBRATOR, A SOURCE OF D.-C. REFERENCE VOLTAGE OPPOSED TO THE SAID D.-C. POTENTIAL PROPORTIONAL TO THE CURRENT OUTPUT, AN AMPLIFIER HAVING AS AN INPUT THE UNBALANCE POTENTIAL BETWEEN THE REFERENCE VOLTAGE AND D.-C. POTENTIAL PROPORTIONAL TO THE CURRENT OUTPUT, AN A.-C. VOLTAGE REGULATOR HAVING AS A CONTROL SIGNAL THE AMPLIFIER OUTPUT, MEANS RECTIFYING THE A.-C. VOLTAGE REGULATOR OUTPUT TO PROVIDE THE D.-C. CALIBRATOR OUTPUT CURRENT, THE REGULATED D.-C. OUTPUT CURRENT BEING OF A MAGNITUDE TO PROVIDE A BALANCE BETWEEN THE SAID D.-C. REFERENCE VOLTAGE AND D.-C. POTENTIAL PROPORTIONAL TO THE SAID CURRENT OUTPUT, AND A VARIABLE TRANSFORMER HAVING A MOVABLE ARM CONNECTING THE OUTPUT FROM THE A.-C. VOLTAGE REGULATOR TO THE SAID RECTIFYING MEANS, THE SAID SOURCE OF D.-C. REFERENCE VOLTAGE INCLUDING A VOLTAGE DIVIDER NETWORK COMPRISING A PLURALITY OF SERIES CONNECTED RESISTORS OF EQUAL RESISTANCE VALUES, A SWITCH HAVING A MOVABLE CONTACT AND A PLURALITY OF FIXED CONTACTS CONNECTED TO THE INDIVIDUAL JUNCTIONS BETWEEN ADJACENT RESISTORS OF THE VOLTAGE DIVIDER NETWORK, THE SAID SWITCH PROVIDING MEANS FOR OBTAINING A PLURALITY OF REFERENCE VOLTAGE VALUES FROM THE VOLTAGE DIVIDER NETWORK, AND MEANS MECHANICALLY COUPLING THE MOVABLE ARM OF THE VARIABLE TRANSFORMER TO THE MOVABLE CONTACT OF THE SAID SWITCH FOR SIMULTANEOUS ACTUATION THEREOF, THE OUTPUT VOLTAGE FROM THE VARIABLE TRANSFORMER INCREASING AS THE REFERENCE VOLTAGE IS INCREASED BY ACTUATION OF THE SWITCH.