Emerson Rosemount 3308A Reference Manual page 115

Reference Manual
00809-0100-4308, Rev CA
2. Set the Near Zone Threshold.
a. Select Service Tools > Echo Tuning > Near Zone > Near Zone Threshold.
b. Under Threshold Control, select User Defined.
c.
changed.
d. Under Threshold, type the desired value into the box.
e.
Reference Point to point where the Near Zone Threshold ends.
Using the trim near zone function
The Trim Near Zone function is used to fine tune performance in the area close to the tank top. Normally
it is not necessary to use the function, but if you experience problems related to the nozzle, pipe, or
chamber installation, you may need to use this function.
Figure 6-14
visible if measurement conditions so require.
Figure 6-14. Echo Curve before and after Trim Near Zone
Reference Peak
Note
Make sure the product level is below the Near Zone region (0-3.3 ft. (0-1 m) below the Upper Reference
Point) before performing the Trim Near Zone.
Note
The Trim Near Zone function should only be used for reducing impact from stationary disturbances. For
occasional disturbances, use the Near Zone Threshold.
To use the Trim Near Zone function:
1. Select Service Tools > Echo Tuning and click Near Zone.
2. Under Near Zone Compensation, select Trim Near Zone and follow the on-screen instructions.
Changing 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
Service and Troubleshooting
PRELIMINARY
If using Field Communicator, select Send. The Threshold and End Distance values can now be
Under End Distance, type the desired value into the box. This value is the distance from Upper
describes the Trim Near Zone function and its effect on the echo curve. This effect is only
Trim Near Zone
Service and Troubleshooting
Reference Peak
August 2017
Figure 6-16.
103