Filtering - Emerson Rosemount 5600 Series Reference Manual

Configuration
March 2020
Double Bounce Offset
4.9.6

Filtering

Distance Filter Factor
Activate Jump Filter
Activate Least Square
Filter
Activate Adaptive Filter
78
Use the Double Bounce Offset to define the distance between detected double
bounces. In order to determine the Double Bounce Offset, you need to check the
spectra of signal amplitude vs. distance to echo or read the detected echoes from
the display. The distance between double bounces is constant. By subtracting two
times the distance to the surface level (2A) from the distance to the first double
bounce (B) you will get the Double Bounce Offset. The Double Bounce Offset is
negative if the reflection point (normally the tank roof) is below the transmitter's
reference point.
DBO = B - 2A
DBO: Double Bounce Offset
B: Distance to first double bounce
A: Distance to surface
Transmitter's reference point
DBO
Double bounce offset
(negative as shown here)
A
Distance to surface
B
Distance to first double bounce
The Distance Filter Factor defines how much the level value should be filtered. A
low factor setting will give the new level value by adding a small portion (for
instance 1%) of the level change to the previous level value. A high factor setting
typically takes the latest measurement and presents it as the new level. This implies
that a low factor setting makes the level value steady but the transmitter reacts
slower to level changes in the tank. A high factor setting makes the transmitter
react quickly to level changes but the level value can be somewhat jumpy.
If the surface echo is lost and a new surface echo is found, the Jump Filter tells the
transmitter to wait for some time before it jumps to the new echo. During that
time the new echo has to be a valid echo. The Jump Filter does not use the Distance
Filter Factor and can be used in parallel to the Least Square Filter or the Adaptive
Filter. The Jump Filter is typically used for applications with turbulent surface and
makes the echo tracking work smoother as the level passes the agitator.
This filter calculates the new level value according to the least square method and
will give increased accuracy for slow filling or emptying of tanks. The level value will
follow the surface with high accuracy and without delay as the level changes. When
the level stabilizes at a certain level, the Least Square Filter makes the level move
somewhat further before it aligns to the correct level value.
The Adaptive Filter is tracking the level fluctuations, and is continuously adjusting
the filter grade accordingly. The filter can preferably be used in tanks where fast
tracking of level changes are important, but where turbulence occasionally cause
unstable level values.
Reference Manual
00809-0100-4024, Rev CA
Tank roof
Configuration