| 摘要 |
PURPOSE:To eliminate drift from concentration, by detecting the concentration of substance in gas or liquid in a way to calculate easily in digital signal processing by determining the transmittance from the phase difference of alternating-current signals. CONSTITUTION:This is an improved version of densitometer to measure the concentration of a substance in gas or liquid from the light absorbing characteristic. This densitometer is equipped with a chopper 10' using rotary polarizing plate, a coefficient multiplier 15', and analyzers 16, 17. The polarizing direction of the analyzer 16 is 45 degree offset from that of the analyzer 17 in the rotating direction of the chopper 10'. The densitometer is further constituted with a semi-transparent mirror 18, a photo detector 19, a phase difference measuring device 22, and a tangent operator 23. Since digital signal processing may be performed easily by using the alternating-current components of phase difference signal 20 and reference phase signal 21 and opening the gate of phase difference measuring device 22 with the rise of the reference phase signal 21 and closing the gate with the rise of the phase signal 20 to count with a clock, appearance of drift in the concentration may be prevented. |
