User's Guide ______________________________________________________________________
86 __________________________________________________________________ M210482EN-B
the sub unit that is suspected to be faulty. In this example, it is
the Ceilometer Transmitter CLT311.
7.
Wait until the 3-minute blower check is over and check the
result from the status message. After this, place a piece of white
paper on the ceilometer window. The blower should start within
one minute. Remove the paper. The blower should stop within
one minute.
8.
If there are clouds present, compare the ceilometer measurement
with a qualified weather observer's height approximation.
9.
In case there are no clouds present and if the site is suitable, do a
hard target test. Turn the measurement unit 90 degrees and aim
it on a fixed target (such as a wall or a forest front).
NOTE
The minimum distance to a hard target should be 300 meters
(1000 ft). The backscatter signal from a hard target is very strong
compared to the signal from a cloud. The receiver may saturate if the
distance is too short.
CAUTION
When tilting the unit, make sure that nobody is watching it with
binoculars or other magnifying optics.
Disable the automatic angle correction by first giving the OPEN
command and then the following commands:
CEILO > SET MESSAGE ANGLE_COR OFF
CEILO > CLOSE
Compare ceilometer's distance reading to a reference
measurement.
Warning and Alarm Messages
This section describes different warning and alarm messages.
Table 18
Warnings
Status Message Info
Reason
Instructions
Window contamination
warning (appears from
time to time and lasts < 5
min).
Usually drizzle drops on the
window.
The blower will clean the window.
If clouds are detected, the height
information is correct. If no clouds
are detected, it is possible that high
clouds are missed.
