| 摘要 |
PURPOSE:To automatically and continuously compensate variation of irradiation light by holding the voltage of an amplification system at a constant value through a variable attenuator according to the deviation between the output voltage of an irradiated light intensity detection signal amplification system and a set voltage and making the output of a particulate scattered light signal amplification system constant. CONSTITUTION:Light emitted by a light source 3 passes through an irradiation lens 4 to illuminates a sample air flow 9 and scattered light from suspended particulates in the air flow is incident on a scattered light detector 5 through a photodetection lens 10. Its output is passed through an amplifier 7 and the particle scattered light signal amplification system into which a variable attenuator 18 is inserted in series and detected by a particulate counter 11. Part of the irradiated light from an irradiated light detector 13 is passed through an amplifier 14 and the irradiated light intensity detection signal amplification system and inputted to a differential amplifier 15. The differential amplifier 15 outputs the deviation between the output of an amplifier 14 and the set voltage to control variable attenuators 17 and 18 through a control element 19.
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