| 摘要 |
PURPOSE:To shorten an operation interrupting period to be generated at the time of the changing-over of a gain, by injecting a current of a predetermined value in the current signal input terminal of an amplifier only for a predetermined period when a feedback resistor is changed over to be connected to a feedback circuit. CONSTITUTION:Radioactive rays are measured by an ionizing box 1 and an output current I1 is amplified by an amplifier 2 to be displayed on a display part through a signal processing part 8. The output voltage V0 of the amplifier 2 is monitored by a voltage monitor apparatus consisting of upper and lower limit setting devices 10, 11, comparators 12, 13, a reversal counter 17 and a decoder 18 and, when said voltage V0 is shifted from a predetermined range, the incremental and decremental operation of the counter 17 is performed and the signal corresponding thereto is outputted from the decoder 18 to drive desired relay driving circuits 19-23 to insert feedback resistors R1-R5. At the same time, a switch driving circuit 30 is driven through an OR circuit 29 and the current of a current generator 32 is injected in the amplifier 2 only for a predetermined time through a switch 31.
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