Emerson Rosemount 3308 Series Reference Manual page 132

Service and troubleshooting
February 2020
Figure 6-13: Echo Curve Before and After Trim Near Zone
A. Reference Peak
B. Trim Near Zone
C. 0-3.3 ft (0-1 m)
Use the Trim Near Zone function
The Trim Near Zone function is used to fine tune performance in the area close to the tank
top (Near Zone).
Prerequisites
Before performing the Trim Near Zone, ensure that:
• There is product in the tank.
• The product level is below the Near Zone region (0-3.3 ft (0-1 m) below the Upper
Reference Point).
Note
The Trim Near Zone function should only be used for reducing impact from stationary
disturbances. For occasional disturbances, use the Near Zone Threshold.
Procedure
1. Select Service Tools → Echo Tuning and click Near Zone.
2. Under Near Zone Compensation, select Trim Near Zone and follow the on-screen
Change the upper null zone
Measurements are not performed within the Upper Null Zone (UNZ). The Upper Null Zone
can be extended to block out disturbing echoes close to the tank top, caused by for
example a narrow nozzle with rough walls, obstacles close to the probe, or a nozzle that
protrudes into the tank. See
132
instructions.
Figure 6-14.
Reference Manual
00809-0100-4308
Rosemount 3308 Series