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Detector
Two light-sensitive detectors are typically used, one for the sample cell and one
for the reference. The detectors output a voltage proportional to the intensity of
the light striking the active area. The type of detectors used varies depending on
the wavelength, which in turn depends on the analyte(s).
GRIN Lens
GRIN is short for graded-index or gradient index. One of the most important
advantages of GRIN lenses compared to classical lenses is that the optical
surfaces of GRIN lenses are flat. This is very important for creating a good
quality joint between the lens and the fiber optics. The GRIN lens in the TDLAS
focuses the laser/fiber-optics package to detect the best signal.
Sample Gas Flow
The sample flows from the inlet thru a Genie filter where any liquid condensate
is removed. The liquid removed flows down the drain vent connection on the
side of the 5100 HD. The gas sample then flows thru the sample cell. Cell
pressure and temperature are monitored using pressure and temperature sensors
respectively. The cell is heated to a maximum of 150C.
Laser Configuration
The laser output is coupled to a single mode fiber, which in turn is connected to
a fiber optic splitter. The splitter is used to divide the optical power for use in the
sample and reference measurements, respectively. The 'sample' output is coupled
to the cell assembly by means of a fiber/Gradient Refractive INdex (GRIN) lens
combination. 'Reference' out put is also similarly coupled to the reference cell.
The GRIN lens helps collimate the output of the single mode fiber and direct the
beam through the sample and reference cells. The beam is reflected by a mirror
at the other end of the cell and is received by a light-sensitive detector at the
originating end.
Measurement
The detector converts the light energy received to an electrical signal and sends
it for signal processing and the analyte concentration determination. WMS and
signal processing are digital providing enhanced quality of analyzer response.
1-6 | Model 5100 HD Analyzer
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