| 摘要 |
In the double-beam spectrophotometer, two light beams, a reference beam and a sample beam, are used. Optical signals in the light beams are converted into electrical signals. The magnitudes of a reference signal and a sample signal are compared. A voltage to be applied to a photoelectric converting means is adjusted on the basis of the difference signal between the larger signal of the compared signals and a reference voltage so that the magnitude of the larger signal is substantially constant. The spectrum displayed by a recorder is obtained by the ratio of the reference signal to the sample signal. Since the larger signal is controlled to be substantially constant, when the sample signal is larger than the reference signal as in the case of a difference spectrum, the photoelectric converting means is not saturated and a wide photometering range is secured.
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