TELEDYNE API T703U - The Absorption Path; Figure 9-20: T703 U O3 Photometer Gas Flow - Measure Cycle; Figure 9-21: T703 U O Photometer Gas Flow - Reference Cycle

Principles of Operation Teledyne API T703/T703U Calibrator Operation Manual
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Figure 9-20: T703U O3 Photometer Gas Flow – Measure Cycle
Figure 9-21: T703U O
3
Photometer Gas Flow – Reference Cycle
The Absorption Path 9.6.1.3.
In the most basic terms, the photometer uses a high energy, mercury vapor lamp
to generate a beam of UV light. This beam passes through a window of material
specifically chosen to be both non-reactive to O
3
and transparent to UV radiation
at 254nm and into an absorption tube filled with sample gas.
Because ozone is a very efficient absorber of UV radiation the absorption path
length required to create a measurable decrease in UV intensity is short enough
(approximately 42 cm) that the light beam is only required to make one pass
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