Emerson 3308A Rosemount 3308 Series, Reference Manual

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93
Reference Manual
00809-0100-4308, Rev BA
Section 6: Service and Troubleshooting
December 2014
Service and Troubleshooting
Figure 6-13. Near Zone Threshold
Guidelines for setting the Near Zone Threshold

The Near Zone Threshold must be higher than the Surface Threshold to have an effect.
The threshold in the near zone is set to the highest value of the configured Near Zone
Threshold and Surface Threshold.

The margin to waveform disturbances and noise must be at least 3 Cnts.
Procedure
To manually set the Near Zone Threshold function, do the following:
1. Read the Echo Curve:
a. Start the Echo Curve reading, refer to “Reading the Echo Curve” on page 83 .
b. View the Echo Curve plot to find out if there are disturbing echoes close to the tank
top.
2. Set the Near Zone Threshold:
a. From the Home Screen, go to Service Tools > Echo Tuning > Near Zone > Near
Zone Threshold .
b. Under Threshold Control , select User Defined .
c. If using Field Communicator, click Send . The Threshold and End Distance values
can now be changed.
d. Under Threshold , type the desired value into the box.
e. Under End Distance , type the desired value into the box. This value is the distance
from Upper Reference Point to point where the Near Zone Threshold ends.
Near Zone Threshold blocking
the disturbance
Surface
Threshold
Reference Peak
Disturbance
Product Surface Peak