| 摘要 |
PURPOSE:To enable the highly precise detection of a peak value and an area integral value by a method wherein a base line value of an input signal before measurement is stored as a digital value and this value is subtracted from an output signal of a photodetector during the measurement. CONSTITUTION:An output signal (a) of photodetector 1 is passed through LPF 2, and thereby a direct-current component (b) is obtained. Simultaneusly with a rise signal at the beginning of measurement, a processing unit 7 delivers a conversion start signal (d) to an A/D converter 4. Next, simultaneously with the end of A/D conversion of the component (b), the processing unit 7 delivers a write signal (e) to a memory 5, and thereby a digital value b' of a base line at the beginning of the measurement is stored in the memory 5. Thereafter the content of the memory 5 are inputted to a D/A converter 5 during the measurement, and a value (f) obtained through D/A conversion of the component in the converter 6 is outputted as the ampli tude of the base line at the beginning of the measurement and inputted to a differential circuit 3. In this circuit 3 the value (f) is subtracted from the signal (a), so as to obtain an output signal (g) formed by separating the component (b) away from the signal (a). This signal (g) is inputted to the processing unit 7, and a peak value or the like is detected thereby and displayed as a signal (h) on a display unit 8.
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