Emerson Rosemount 3308A Reference Manual page 116

Service and Troubleshooting
August 2017
Note
Desired measuring range must be below the Upper Null Zone.
Note
Before changing the Upper Null Zone, check entered limit and deadband values for the High Level Alerts.
High Level Alerts should not be placed in the Upper Null Zone.
To set the Upper Null Zone:
1. Identify desired Upper Null Zone using the Echo Curve plot.
a. Start the Echo Curve reading, refer to
b. View the Echo Curve plot to find out if there are disturbing echoes close to the tank top.
2. Set the desired Upper Null Zone value.
a. Select Configure > Manual Setup > Level Setup > Probe > Advanced Probe Options.
b. Under Upper Null Zone, type the desired value into the box, and then select Send.
Figure 6-15. Upper Null Zone
A. Upper Reference Point
B. Upper Null Zone
C. Measurement Range
Figure 6-16. Upper Null Zone Is Extended to Block Out Disturbances at the Top of the Tank
A. Upper Null Zone
B. Disturbance
C. Product Surface Peak
104
PRELIMINARY
A
B
C
A
B
C
3.0
DISTANCE
"Reading the echo curve" on page
5.0
Reference Manual
00809-0100-4308, Rev CA
93.
Service and Troubleshooting