7.10 Application challenges
7.10.1 Handling disturbances at top of tank
In addition to using the ATC, the Rosemount 5300 Level Transmitter supports alternative
methods to filter out disturbances at the top of the tank, such as the Trim Near Zone and
the Hold Off Distance/Upper Null Zone functions, which can be used to handle
disturbances from narrow nozzles or nozzles with rough edges.
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). The Near Zone stretches about 3.3 ft (1 m) into the tank from the lower
side of the device flange.
The device will learn how the echo curve in the Near Zone looks like and use this for
enhancing accuracy when the surface echo is within the Near Zone. When leaving factory,
the near zone measurement has been fine tuned. The factory setting is normally sufficient
and does not need to be repeated after installation.
However, since the setting is optimized depending on actual installation, further trimming
may be necessary in the case of unfavorable conditions (for instance if there are
disturbance echoes caused by the tank nozzle, or if you have exchanged the probe).
Trimming means that the measurement performance in the Near Zone is maintained even
under these conditions and prevents false echo indication.
Figure 7-28 describes the Trim Near Zone function and its effect on the echo curve. This
effect is only visible if measurement conditions so require.
Service and troubleshooting Reference Manual
April 2019 00809-0100-4530
224 Rosemount 5300 Level Transmitter
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