Chapter 6 ______________________________________________________________ Maintenance 
VAISALA ______________________________________________________________________ 209 
 
14.  Re-install the measurement head cover and lock it carefully. 
15.  Close the interface unit and mount the upper interface unit cover 
after fine alignment and calibration is finalized. 
Replacing Transmitter Optics Unit 
LTO112 
NOTE 
To replace the complete receiver optics unit, the receiver measurement 
unit has to be opened. For this reason, it is highly recommended to 
dismount the complete measurement unit and carry out the replacement 
work on a clean workbench in a dry room. 
 
To remove the complete transmitter measurement unit, the AC power has 
to be switched off first and then the measurement head cover has to be 
removed. 
1.  Remove the upper interface unit cover and open the interface unit 
with the provided key. 
NOTE 
Switch the AC switch off, before you proceed with the next steps. In 
case of the optional LTBB111, switch the battery backup switch off as 
well. See Figure 40 on page 83. 
 
2.  Loosen the three lock screws at each side of the measurement head 
cover and carefully remove the cover from the measurement head. 
See Figure 95 on page 140. 
3. 
The measurement unit is fixed with two fastening screws. Through 
the mast adapter of the support unit, these two hex- socket screws, 
size 4, can be reached. See Figure 78 on page 118. 
The following steps should be carried out in a closed room
. The 
measurement unit cover has to be opened carefully. 
1.  Loosen the four fastening screws of the cover plate, hex-socket, 
size 5 and remove the cover with air duct. See Figure 72 on page 
115. 
2.  To remove the optics unit, two fastening screws (hex-socket size 3) 
and one fastening bolt (socket wrench, size 7) have to be loosened. 
See Figure 121 on page 210.