| 摘要 |
In a double beam, optical-null type infra red spectrophotometer, an optical system including a movable dispersive optical element causes transmission of a spectrum of light in respective beams through an adjustable optical attenuator and through a sample and thence to a sensing circuit. The sensing circuit provides an error voltage having an amplitude proportional to the difference between the intensites of the beams passing through the sample and through the attenuator respectively. The position of the attenuator is adjusted in proportion to the integral of the error voltage to cause a reduction thereof while, in response to the magnitude of the error voltage in excess of a threshold value, there is a reduction in the rate of movement of the dispersive element.
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