| 摘要 |
PURPOSE:To save a space by providing a counting rate calculating element which calculates a counting rate of this time on the basis of a pulse signal count value, a selecting element which compares the counting rates of this time and the last time with each other and selects the one meeting the condition, etc. CONSTITUTION:When radiation enters a pulse-type radiation detector 1, first, an output pulse corresponding to the strength of the radiation is outputted from this detector 1 and it is amplified by an amplifier circuit 2 and then inputted to a counter circuit 3. The circuit 3 conducts level discrimination at a level corresponding to a peak value of the output pulse supplied from the circuit 2 and filters noise, and then it counts the pulse and supplies a count value thereof to an arithmetic circuit 4. The circuit 4 collects the count value every time when it is supplied from the circuit 3, determining a counting rate of this time on the basis of the time passing from the supply of the count value of the last time to the supply of that of this time and the count value supplied this time and comparing it with the counting rate of the last time. Next, the circuit 4 determines a time constant by determining an increase or decrease of the counting rate, executes an operation to determine the counting rate to be outputted this time, and outputs it.
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