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1
Introduction
Functional Description
Functional Description
Figure 2.
The PDA detector optical system
Deuterium
Beam combiner
lamp
Attenuators
2
Accela PDA Detector Hardware Manual
The detector is a full-featured, time-programmable, photodiode array (PDA) detector capable
of scanning the ultraviolet-visible wavelength range from 190 to 800 nm. You can acquire
data across the entire spectral range (with an effective resolution of 1.2 nm) at a rate of 0.5 to
80 Hz with 20-bit digital conversion.
The PDA detector is a benchtop unit for inclusion in the Accela liquid chromatography
system. You control the detector through an Ethernet link to a data system computer that has
the Xcalibur™ or ChromQuest™ data system installed. The detector consists of a dual-light
source, an optical bench, a photodiode array, a low voltage power supply, several printed
circuit boards (PCBs), and four status light-emitting diodes (LEDs).
Figure 2
shows the optical system used in the detector. The dual-light source includes a
deuterium lamp for detection in the ultraviolet wavelength range (190 to 360 nm) and a
tungsten-halogen lamp for detection in the visible wavelength range (360 to 800 nm). The
light output from the two lamps overlaps in the 300 to 500 nm range. You can increase or
decrease the light intensity reaching the photodiode array by manually adjusting the
attenuator for the deuterium lamp and the attenuator for the tungsten lamp.
The optical bench contains a beam combiner, focusing lens, filter wheel, LightPipe flowcell,
beam shaper, folding mirror, and grating. The beam combiner reflects the light coming from
the tungsten-halogen lamp so that it is parallel to and coincident with the light from the
deuterium lamp. A lens focuses the combined beam on the inlet window of the LightPipe
flowcell through the filter wheel. The standard filter wheel has two positions. For normal
operation, leave the filter wheel in Position 1 (Open). Position 2 contains a sealed quartz
cuvette filled with a holmium oxide/perchloric acid solution (traceable to NIST) used for
wavelength accuracy verification and calibration.
Focusing lens
Filter wheel
Fixed grating
Tungsten-halogen lamp
LightPipe flowcell
Beam shaper
Folding mirror
×
1
512
photo diode
array
Thermo Scientific
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