| 摘要 |
PURPOSE:To keep constant output characteristic of a photoelectric multiplier tube with independent adjustment of preamplifier gains, by comparing the peak value of an energy signal outputted from a photoelectric amplifier tube with a reference value to set adjusting conditions of a preamplifier gain fine adjustment circuit according to a deviation therebetween. CONSTITUTION:A channel containing a light source Ra, a photoelectric multiplier tube Ta, an automatic gain adjustment circuit 2a and a preamplifier 3a is selected and a switching signal is sent to analog switches 9a-9c to set a resistance value corresponding to a preset value. The current peak value of a spectrum is sent to a comparator 8 to be compared with a reference peak value. According to a deviation as the results of the comparison, the switch 9a-9c are changed over to determine the new gains of the preamplifier with the readjustment of the gain thereof for the respective photoelectric multiplier tubes. This procedure is carried out at a proper cycle utilizing the time excluding the collection time of image data from each channel thereby allowing an automatic tuning with less variations in individual channels.
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