Teledyne T100, Инструкция по эксплуатации, Страница: 224 / 404

Theory Of Operation Teledyne ML - T100 UV Fluorescence SO2 Analyzer
224 06807A(DCNxxxx)
The Model 100 E UV Fluorescence SO
2
Analyzer is specifically designed to create these
circumstances.

The light path is very short ( x ).

A reference detector measures the intensity of the available excitation UV light and is used
to remove effects of lamp drift (
I
0
).

The temperature of the sample gas is measured and controlled via heaters attached to the
sample chamber so that the rate of decay (
k ) is constant.

A special hydrocarbon scrubber removes the most common interfering gases from the
sample gas.

And finally, the design of the sample chamber reduces the effects of stray light via its optical
geometry and spectral filtering.
The net result is that any variation in UV fluorescence can be directly attributed to
changes in the concentration of SO
2
in the sample gas.
9.1.2. THE UV LIGHT PATH
The optical design of the T100’s sample chamber optimizes the fluorescent reaction
between SO
2
and UV Light (refer to Figure 9-2) and assure that only UV light resulting
from the decay of SO
2
* into SO
2
is sensed by the instruments fluorescence detector.
UV radiation is generated by a lamp specifically designed to produce a maximum
amount of light of the wavelength needed to excite SO
2
into SO
2
* (214 nm) and a
special reference detector circuit constantly measures lamp intensity (refer to (Equation
9-2)). A Photo Multiplier Tube (PMT) detects the UV given off by the SO
2
* decay (330
nm) and outputs an analog signal. Several focusing lenses and optical filters ensure that
both detectors are exposed to an optimum amount of only the right wavelengths of UV.
To further assure that the PMT only detects light given off by decaying SO
2
* the
pathway of the excitation UV and field of view of the PMT are perpendicular to each
other and the inside surfaces of the sample chamber are coated with a layer of black
Teflon
®
that absorbs stray light.