May 2016
Reference Manual
00809-0100-4530, Rev DD
302
C.3.2
Changing the Hold Off Distance/Upper Null Zone (UNZ)
The Hold Off Distance/UNZ defines how close to the Upper Reference Point a level value is
accepted. You can extend the Hold Off Distance/UNZ to block out disturbing echoes close
to the tank top, see
Figure C-3. Hold Off Distance/UNZ
Note
By adjusting the Hold Off Distance/UNZ, the measuring range is reduced.
Use the Echo Curve plot to verify if there are disturbances in the upper part of the tank, see
.
Figure C-4. Identifying the Hold Off Distance/UNZ in the Echo Curve Plot
Hold Off Distance/UNZ
Surface Threshold
Disturbance
Upper Reference Point
Surface peak
3.0
5.0
Hold Off Distance/UNZ
Disturbance
Am
pl
it
u
d
e,
m
V
Distance, m
Surface Threshold
Surface peak