Dual-wavelength absorption detector adapted for continuous-flow detection

摘要

A dual-wavelength absorption detector is provided. The detector includes an electronics section, a three branched optical guide and a detector-cell. Each branch of the optical guide has a plurality of fibers, and at one end the branches are separated and connected to different portions of the electronics section. Two of the three branches are terminated next to LEDs having different wavelengths, a measuring wavelength and a reference wavelength. The third branch is terminated next to a photodetector. At the opposite end of the optical guide the three branches are combined to form a common end which is terminated within the detector-cell. The detector-cell includes a continuous-flow sample cell connected to a sample line. Within the detector-cell, the common end's fiber ends are held at a fixed location on one side of the sample cell with a concave mirror being located on the opposite side. Sequential pulses of light from the LEDs are guided through their respective branches to the common end where they cross the sample cell to be absorbed by sample material flowing through the cell. Portions of each pulse are reflected by the concave mirror back across the sample cell to the common end and strike the photodetector branch fiber ends. At the photodetector, signals proportional to the illumination intensity of the pulses striking the fiber ends are produced. The signals are then compared to provide an output signal which represents the absorption of the sampled material.