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Adjusting the Light Throughput with the ChromQuest Data System
Thermo Scientific
The Accela PDA Detector has two attenuators that control the light throughput from the
lamps.
Decreasing light throughput increases baseline noise. Increasing light throughput can saturate
the diode array. When the array is saturated, the response from the Accela PDA Detector is a
flat baseline.
Adjust the attenuators as the light output from the deuterium lamp decreases and whenever
you do the following:
• Replace either lamp (see
• Replace the LightPipe flowcell (see
• Change the configured diode array scan rate (see
Tip As the diode array scan rate increases, the sampling time per diode decreases. The
integrated light intensity viewed on the Display page is a function of the light throughput
to the diode array and the sampling time per diode. So when you change the diode array
scan rate, you must adjust the light throughput.
• If you increase the diode array scan rate (for example, from 20 Hz to 80 Hz), you
must increase the light throughput to achieve the same intensity counts.
• If you reduce the diode array scan rate (for example, from 80 Hz to 20 Hz), you must
reduce the light throughput to avoid saturating the array.
Pushing the attenuator tabs upward increases the light throughput to the diode array.
Pushing the attenuator tabs down decreases the light throughput to the diode array. (See
Figure 20
on
page
25.)
Check the light intensity by following the Operational Verification procedure and adjust the
attenuators to provide light intensities in the specified operating ranges.
Note Before you adjust the attenuators, replace the column with a flow restrictor, and set
the pump to deliver HPLC-grade water at a flow rate of 1 mL/min through the flowcell.
To adjust the light throughput from the lamps, follow these procedures:
1.
Setting Up the Spectral and Discrete Channel Displays
2.
Adjusting the Attenuators
5
Adjusting the Light Throughput with the ChromQuest Data System
"Replacing the Lamps"
on
"Installing the LightPipe Flowcell"
Chapter 3, "Configuration."
ChromQuest Diagnostics for the PDA Detector
page
89)
on
page
Accela PDA Detector Hardware Manual
17)
)
69
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