Detector Control
Adjusting the Light Throughput (Accela PDA 80 Hz)

During the lamp’s lifetime, the lamp’s light output decreases. Manually adjust the attenuators on the Accela PDA 80 Hz detector as the light output from the lamps decreases.

 

When to Adjust the Light Throughput:

After replacing the lamp

After replacing the LightPipe flowcell

After changing the maximum data collection rate in the Server Configuration

 

To adjust the light throughput:

  1. Connect the detector in Chromeleon.

  2. Verify that the lamps are turned on and equilibrated (wait for 1 hour).

  3. Pump methanol through the flowcell at 1 mL/min.

  4. Open the Accela PDA Control Panel. Click Light Levels to open the light throughput subpanel.

  5. Click Start Light Throuput Adustment. The intensity readings for Channels A, B, and C are displayed in the related boxes.

  6. Click Take Intensity Scan to display the current intensity spectrum in the plot window. In addition, the intensity scan is saved to a Spectra Library named Accela PDA.lib in the Manual sequence of the timebase. Any intensity scans are stored and can be used for future comparisons to see if there is degradation in light intensity.

  7. Adjust the left attenuator tab (UV attenuation) on the detector to achieve a Channel A value as close as possible to 400000–900000 intensity counts without saturating the array.

  8. Adjust the right attenuator tab (Visible attenuation) on the detector to achieve a Channel C value as close as possible to 900000 intensity counts without saturating the array.

  9. Click Stop Light Throughput Adjustment.

 Notes:

If you increase the data collection 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 data collection rate (for example, from 80 Hz to 20 Hz), check the intensity counts, and if necessary reduce the light throughput to avoid saturating the array.

Also, refer to the Accela PDA Detector Hardware Manual.