User guide

Principles of Operation Model 6200T Total Sulfur Analyzer
292 Teledyne Analytical Instruments
13.1.7.2. PMT Optical Filter
The PMT used in the 6200T reacts to a wide spectrum of light which includes much of
the visible spectrum and most of the UV spectrum. Even though the 214 nm light used
to excite the SO
2
is focused away from the PMT, some of it scatters in the direction of
the PMT as it interacts with the sample gas. A second optical band pass filter placed
between the sample chamber (refer to
Figure 13-2) and the PMT strips away light outside of the fluorescence spectrum of
decaying SO
2
* (refer to
Figure 13-5) including reflected UV form the source lamp and other stray light.
LAMP OUTPUT
(Arbitrary Untis)
10
5
10
4
10
2
10
3
10
1
1
100 200 300 400 500
WAVELENGTH (nm)
0
213.9
330.3
SO
2
* FLUORESCENT
SPECTRUM
PMT OPTICAL FILTER
BANDWIDTH
Figure 13-5: PMT Optical Filter Bandwidth