PURPOSE:To enable to perform a high-reliable, high-precise counting, by a method wherein both crest amplification and dose rate counting are simultaneously controlled by means of a signal which causes starting and stopping of counting. CONSTITUTION:An output pulse from a radiation detector 1 receives in a circuit 6 a delay time which is equivalent to a load function value, corresponding to the crest of the output pulse. Meanwhile, a counting control circuit 10 generates a starting and a stopping signal which correspond to the interval of a delay time by means of each output signal from crest discriminating circuits 3 and 7 for counting start and counting stop, respectively. A generating circuit 8 outputs a reference signal, having a constant frequency, for the period during which a starting and a stopping signal are generated, and an enumerated value obtained in a digitable circuit 9 is indicated as a dose rate. The starting and the stopping signal control a crest amplifying control circuit 11 as well, and the passage of an output of a linear amplifier 2 is checked between the starting and stopping signal.
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