4
Xcalibur Diagnostics for the PDA Detector
Calibrating the PDA Detector
Thermo Scientific
Surveyor PDA Plus Detector Hardware Manual
39
Performing a Dark Current Calibration
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 1500 to 3000 counts.
The environmental conditions of your laboratory can cause the dark current of the diode
array to increase over time. Therefore, Thermo Fisher Scientific recommends performing 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 download a new firmware file
Because the dark current produced by the diodes rises as the temperature within the detector
rises, it is important to warm up the lamps for 1 hour before performing a dark current
calibration. Warming up the lamps for 1 hour equilibrates the detector to its normal operating
temperature.
The lamps turn off briefly as the detector performs the dark current calibration routine. After
it completes the dark current calibration routine, the lamps turn back on.
To perform the dark current calibration
1. Pump methanol through the flow cell at 1 mL/min.
2. Turn on both lamps and wait 1 hour for the lamps to equilibrate.
3. On the menu bar of the Surveyor PDA Plus Detector Instrument Setup window, choose
Surveyor PDA > Direct Control
. Then click the
Calibration
tab to open the
Calibration page.
shows the readback display for an uncalibrated detector.
