| 摘要 |
PURPOSE:To enable lengthening of a measuring time and the improvement of a precision, by a method wherein, when an output of an integrating capacitor, whereto a voltage corresponding to a measurement current is applied, is produced into a given level, a reference voltage is applied in an overlapping manner to the capacitor. CONSTITUTION:With a switch 7 closed, a measurement current 1 flows to a load resistance 2, and voltages at the opposite ends of the resistor 2 are integrated by means of integrating circuits 4, 5, and 6. If an output of an operational amplifier 4 reaches a voltage of a reference voltage source 31, a comparator 32 actuates, a switch 8a is closed and a switch 8b is opened through a program-setting circuit 13 to flow a reference current 9 to the load resistance 2, and simultaneously, to open a gate 15. After a given time has elapsed after measurement starts, the switch 7a opens and 7b closes, and at the point of time when the output of the operational amplifier 4 is brought into a null position, the gate 15 closes. A clock pulse from a pulse generator 14, passing through the gate 15, is counted to measure a measurement current. This increases a ratio of the measurement time to a measuring period, and permits the reduction of the influence exerted by disturbance. |
