| 摘要 |
PURPOSE:To prevent the suffocation of a counting rate meter in a simple constitution by detecting the output-side high-voltage current of a high-voltage power source, which activates a GM counter tube, by a photo coupled transistor to control an indicator. CONSTITUTION:A high-voltage current is flowed to load 14 from high-voltage power source according to measured energy, and instrumentation pulses dependent upon pulse shaping and amplifier circuit 18 are counted by pulse counting rate meter 19 on a basis of the radioactivity detection output of GM counter tube 13 which is activated by the high voltage of load 14, and the radioactivity strength is indicated on indicator 23. The high-voltage current in the output side of power source 16 is detected as a voltage by photo coupled transistor 25 provided in high-voltage current detection circuit 15 connected to the output side of power source 16 and is applied to comparator 28 of indication holding circuit 20 where a reference voltage is set. Then, when the high-voltage current exceeds a prescribed value, the output of comparator 28 generates a high- level output and applies it to indicator 23, and indicator 23 is caused to perform display over full scale, so that the generation of suffocation phenomena can be prevented in a simple constitution in comparison with detection of the current in the ground side of the high-voltage power source.
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