Teledyne UA-6, Installation And Operation Manual

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UA-6 Detector
Section 4 Theory of Operation
4-9
Light radiating through the reflector aperture, then through the
measuring flow cell, is filtered and passed to a photodetector.
Both filter assemblies, which are matched in wavelength to the
source screen, transmit a narrow spectral region. The resultant
output from the filter assemblies is applied to two photodetectors
which generate an electrical resistance that is inversely propor-
tional to the amount of light projected onto the photosensitive
surfaces. Any increase in the light intensity results in a decrease
in the electrical resistance generated by the photodetectors.
Outputs from the photo¬detectors are transmitted to an absor-
bance detector control system, which reflects these photodetector
outputs as units of absorbance.
Figure 4-3 Type 11 Optical Unit Functional Diagram
With respect to the 254 nm, 280 nm, 310 nm, and 340 nm filter
assemblies, the UV lamp produces numerous discrete emission
lines, with a very prominent one at 254 nm. The fluorescence
filter assembly, which is located in the light path after the light
has passed through the flow cell, consist of these main elements.
• A UV-transmitting filter that blocks green visible light.
• A fluorescent layer that produces green fluorescence
when excited by UV light.
• Green transmitting filter.