Near Zone Threshold - Emerson Rosemount 3300 Series Reference Manual

Reference Manual
00809-0600-4811, Rev AA
February 2009

Near Zone Threshold

Figure 5-9. A disturbing echo
from the nozzle is erroneously
marked as the product surface.
Figure 5-10. The Near Zone
Threshold hides the disturbing
echoes.
Rosemount Radar Level Transmitters
Disturbing echoes may result from rough edges in the nozzle. Figure 5-9
illustrates that this may cause the transmitter to identify the wrong peak as the
product surface.
If the product surface is not located as close to the nozzle as indicated in the
waveform plot, set the Near Zone Threshold. The amplitude threshold T2 can
be adjusted to filter out disturbances close to the nozzle. The adjusted
threshold T2 correctly detects the surface peak, as illustrated in Figure 5-10.
Near Zone threshold
5-7