Rosemount 5600 Series, Справочное руководство

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Reference Manual
00809-0100-4024, Rev BA
September 2005
Rosemount 5600 Series
4-17
Double Bounce Possible Some radar waves are reflected against the tank roof and back
to the surface before they are detected by the transmitter.
Normally, these signals have a low amplitude and are therefore
neglected by the transmitter. For spherical and horizontal
cylinder tanks, in some cases the amplitude may be strong
enough to lead the transmitter to interpret the double bounce
as the surface echo. By setting the Double Bounce parameter
this type of measurement situation may be improved.
This
function should only be used if the problem of double
bounces can not be solved by changing the mounting
position.
Double Bounce Offset 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
Actual level
Virtual level. After
the signal is
mirrored in the
product surface and
the roof, this level
may be presented
as actual level.
5600_C_07A.EP
S
Tank Roof
Transmitter’s reference point
Double bounce offset
(negative as shown here)
Distance to surface
Distance to first double bounce
B
A
DBO
5600_C
_08A
.E
P
S