Campbell Scientific CS135 Lidar Ceilometer - Manual (Page 18)

CS135 Ceilometer
10
Remove the washers and nuts from the protruding length screw. Then lower the
CS135 into place. If you plan to tilt the unit make sure it is orientated so that when
tilted in the preferred direction the window angle steepens.
Finally, secure the CS135 with the washers and nuts.
If the surface is not level and flat it may be necessary to add washers under the
base on one or more of the foundation screws.
Fig 4.1 Mounting footprint
4.4 Tilt Angle
The CS135 is designed to be tilted 6°, 12°, 18° or 24° from vertical. There are
several reasons why this might be done. In tropical regions it might be
advantageous to tilt the sensor north in the northern hemisphere and south in the
southern hemisphere to prevent the sun shining directly into it, it can reduce
problems caused by direct specular reflections from ice crystals and reduce
problems from rain or snow falling onto the window. To adjust the tilt angle
remove the bolts shown in Fig 4.2, move the CS135 to the required tilt angle and
replace them.
The CS135 has tilt sensors in both axes so that if it is not possible to provide a
level base cloud height can be compensated. This feature can be useful for mobile
or marine applications. Note that profile data is NOT compensated but tilt angles
are included in data messages.
Note that increasing the tilt angle beyond 24° can cause significant errors in
vertical visibility measurements if scatter coefficients vary significantly with
height.