SPECTROPHOTOMETER

PURPOSE:To improve rectilinearity of an absolute value and to widen a dynamic range, by a method wherein a parallel current voltage amplifier or a logarithmic amplifier, which processes a photospectrometric detecting value by a photo detector, is switched in synchronism with switching of an optical path to sample chambers at a measurement side and a reference side. CONSTITUTION:By means of a synchronizing signal, alternately switching optical paths to a sample chamber 3 at a measurement side and a sample chamber 4 at a reference side of a spectrometer body 1 through the working of a synchronizing signal generating circuit 29, and a signal from the synchronizing signal generating circuit 29, switches S1 and S2 for a current voltage amplifier 22 and a logarithmic amplifier 27, respectively, are controlled. In case the amplifier 22 performs an amplifying motion through closing of the switch S1 and application of a negative feedback, the switch S2 of the amplifier 27 is opened, and the amplifier 27 is prevented from operating. A spectrometric detecting value by an electron multiplier 5 is directly amplified by a switching, and this constitution improves rectilinearity of anabsolute value, and permits the widening of a dynamic range, which results in bringing of logarithmic conversion output data into high reliability.