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4
Xcalibur Diagnostics for the PDA Detector
Calibrating the PDA Detector from the Xcalibur Data System
Calibrating the PDA Detector from the Xcalibur Data System
Performing a Dark Current Calibration from the Xcalibur Data System
44
Accela PDA Detector Hardware Manual
To calibrate the PDA detector from the Xcalibur data system, follow these procedures:
•
Performing a Dark Current Calibration from the Xcalibur Data System
•
Performing a Wavelength Calibration from the Xcalibur Data System
The Array calibration measures and corrects for the dark current produced by the diodes of
the photodiode array. The dark current is the small amount of background signal that is
produced by the diodes of the array even when both lamps are turned off. Typical dark current
values range from 2000 to 4000 counts.
The environmental conditions of your laboratory can cause the dark current of the diode
array to increase over time. For best results, perform an array calibration (dark current) after
any of the following events occurs:
• After 100 hours of use or monthly, whichever comes first
• Whenever a significant temperature change occurs
• After you move the detector
• After you replace the lamp
• After you update the firmware by placing a new firmware file in the data system directory
Because the dark current produced by the diodes rises as the temperature within the detector
rises, warm up the lamps for one hour before you perform a dark current calibration.
Warming up the lamps for one hour equilibrates the detector to its normal operating
temperature.
The PDA detector briefly turns the lamps off as it performs the dark current calibration
routine. After it completes the dark current calibration, the PDA detector turns the lamps
back on.
To perform the dark current calibration from the Xcalibur data system
1. Pump methanol through the flowcell at 1 mL/min.
2. Turn on both lamps and wait one hour for the lamps to equilibrate (see
Lamps from the Xcalibur Data System"
Control dialog box open.
3. Click the Calibration tab.
The Calibration page appears (see
on
page
35). Leave the Accela PDA Direct
Figure
33).
"Controlling the
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