TWP/VCEIL/C3 - Reduced sensitivity to high clouds

The instrument produced a significant number of optical cross-talk warnings and displayed 
a reduced capacity to detect high clouds.  The internal cables were inspected, the 
compensation fiber and optics monitor were replaced, the crosstalk compensation was adjusted, 
and the system tested with an optical termination hood, all with no improvement.  While 
waiting for a new receiver board, receiver ribbon cable, and compensation fiber cable from 
Vaisala, a spare ceilometer with a standard, "non-tropics", window was installed.

• Second lowest cloud base height(second_cbh)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Altitude of highest signal(alt_highest_signal)
• Detection status. See details(detection_status)

TWP/VCEIL/C2 - optical cross-talk compensation

The ceilometer gave frequent optical cross-talk compensation warnings, was insensitive to 
high clouds, and the tropics window was deteriorated. The instrument was replaced with a 
spare.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Millivolts at internal ADC input(window_contamination)

TWP/VCEIL/C2 - Receiver failure

The receiver failed and the instrument was replaced.  Data during the specified period are 
not valid.

• Aerosol backscatter coefficient at 355 nm(backscatter)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Backscatter sum(sum_backscatter)

TWP/VCEIL/C3 - Reduced sensitivity to high clouds

The instrument had reduced sensitivity to high clouds.

The instrument produced a significant number of optical cross-talk warnings and displayed 
a reduced capacity to detect high clouds. The window was cleaned and the instrument was 
power-cycled but with no improvement. Diagnostics indicated the problem was with the 
compensation fiber cable. 

The problem was corrected by replacing this standard-window instrument (that was tilted at 
16 degrees) with a tropics unit that became available.

• Vertical visibility(vertical_visibility)
• Second lowest cloud base height(second_cbh)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Altitude of highest signal(alt_highest_signal)