Humminbird LCR 3D - Manual (Page 26)

4. The depth readout can be changed from feet to meters.
To adjust any of these functions, press ENTER until the black box preceding the function is
blacked-in, use the UP and DOWN arrow keys to adjust the setting, and then press SELECT if no
other adjustments are required.
8. Using Diagnostic
Factory setting: OFF
The Diagnostic function displays "raw" sonar
information from the four beams individually. By
comparing the four returns it is possible to fine tune your
installation and to troubleshoot problems with the system.
The top of the return is the origination of the signal
or the surface of the water, and the large area of the return
is the bottom. Any deviations in the area between the two
are fish or other targets not attached to the bottom. The
horizontal width of the bottom return represents the
strength of the sonar signal reflected off the bottom.
Diagnostic is especially helpful when installing the
sensor of the LCR 3D, since the strength of an individual
beam can be compared to the other beams. This feature
can be used to ensure that the location you have chosen
for the sensor is not degrading the performance of the
LCR 3D. A noticeably weaker signal in one beam than in the others indicates a problem with the
sensor location. By comparing readings taken from various inside hull locations to those taken
outside the hull relative signal loss, and thus performance, for inside hull mounting can be
determined.