The LD40 Laser Ceilometer Satus Flag

The LD40 laser ceilometer performs a number of self-check and self-adjustment routines for each 15 s measurement cycle. Error and warning messages are coded within an 8 digit instrument status integer. A value of 99999999 implies that no observations were made. Zeros in the first seven digits imply that the instrument was functioning correctly. The interpretation of individual digits is as follows:

Status Digit 1 (most significant digit): Power supply

0: Power supply OK.

1: +/-5 V or +/- 12 V supply failure.

2: Not used.

3: Avalanche photodiode voltage regulator failure.

4: Test laser voltage regulator failure.

5: Original laser voltage regulator failure.

6: No response from AD/DA converter.

Status Digit 2: Window backscatter and solar shutter

0: Window backscatter and solar radiation measurements within allowed range.

1: Window scatter > 50%. Window requires cleaning.

2: Solar radiation too strong. Shutter is closed.

Status Digit 3: Receiver

0: Receiver OK.

1: Offset too low.

2: Offset too high.

3: Not used.

4: Receiver sensitivity too low. Error. No more measurements possible.

5: Receiver sensitivity too low and offset too low.

6: Receiver sensitivity too low and offset too high.

Status Digit 4: Original laser and test laser

0: Transmitter module OK.

1: Laser power low. Warning only. Measurements continue.

2: Laser power too low. Error. No more measurements possible.

3: Not used.

4: Not used.

5: Test laser failure. Error. No more measurements possible.

6: Original laser switched off.

Status Digit 5: Flash-ADC

0: Flash-ADC OK.

1: One flash-ADC error during regulation of the bias voltage of the avalanche photodiode.

2: Several flash-ADC errors during regulation of the bias voltage of the avalanche photodiode.

3: Flash-ADC failure.

4: Flash-ADC too slow during normal measurements. No reply.

Status Digit 6: Temperature regulation

0: Temperature regulation OK.

1: Temperature controller defect.

Status Digit 7: Reset and data reception

0: Data transmission OK.

1: Sensor will perform a reset.

2: Not used.

3: Not used.

4: Not used.

5: Not used.

6: Not used.

7: Received and calculated checksum differ.

8: Received command message is too long.

Status Digit 8 (least significant digit): Setup information

0: Current setup is the setup stored in the EEPROM.

1: EEPROM failure. Current setup if the default setup.

2: Setup has been changed by the user and is different from the EEPROM and default setups.

3: Not used.

4: In case of failures, the message contains dashes instead of data.

5: EEPROM is defective. Current setup is the default setup and the message contains dashes instead of data.

6: Setup has been changed by the user and is different to the EEPROM and default setups. The message contains dashes instead of data.

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Description of the instrument, of the measurement procedure and of the meaning of the data products.

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