Emerson Rosemount 5408 Reference Manual page 213

Reference Manual
00809-0100-4408, Rev BA
This function requires the Bottom echo visible when tank is empty parameter to be disabled.
Bottom echo visible when tank is empty
Only enable this parameter if the bottom echo is visible when tank is empty. By setting this parameter,
the bottom echo will be treated as a disturbance echo to facilitate tracking of weak surface echoes close
to the tank bottom (see
Tank bottom projection
The Tank Bottom Projection is used to enhance measurement performance near the bottom of the tank.
When the tank bottom echo is strong (typical for flat tank bottoms) and the dielectric constant of the
product is low (e.g. oil), the transmitter may lock on the bottom echo and report a false level
measurement (empty tank). This problem can be solved by using the Tank Bottom Projection function.
See "Tracking of weak surface echoes close to tank bottom" on page 108
Bottom product dielectric constant
Enter the product dielectric constant for the product in the bottom of the tank.
Maximum projection distance
This defines the range where the function is active. Enter the maximum distance from the zero level
(tank bottom).
Minimum tank bottom amplitude
Enter the minimum allowed amplitude for the echo from the tank bottom before this function is
activated.
Echo tracking
Surface echo tracking
Use these settings to configure how the transmitter should keep track of the surface. These are advanced
settings. Normally, they should not be changed.
Search window size
This parameter defines a window centered at the current surface position where new surface echo
candidates can be selected. The size of the window is ±Search Window Size. Echoes outside this window
will not be considered as surface echoes.
If there are rapid level changes in the tank, the value of the Search Window Size can be increased to
prevent the transmitter from missing level changes. On the other hand, a large value may cause the
transmitter to select an invalid echo as the surface echo.
Track first echo
Select the Track First Echo check box if the first echo above threshold always should be considered as the
surface echo (see
Double surface handling
If there are multiple products in the tank, the Double Surface Handling function can be manually set to
allow user to select if the upper or lower product should be used as output.
The upper and lower surface echoes must be stronger than any disturbance echoes in the search region
for Double Surface Handling to function properly.
Track upper surface
Track upper surface when there are multiple products in the tank (for example thin oil layer on top of
water).
Configuration Parameters
"Enable bottom echo visible when tank is empty" on page
"Handling ghost echoes in still pipes" on page
Configuration Parameters
November 2017
108).
for further instructions.
110).
201