Rosemount 5401, Reference Manual

Page: 171 / 180

Reference Manual
00809-0100-4026, Rev FA
July 2009
C-11
Rosemount 5400 Series
Double Bounce
A double bounce echo is an echo that has been reflected against the tank roof
then down to the surface before being detected by the transmitter.
Double bounces are commonly present in spherical or horizontal cylinder
tanks. In this case, the tank roof can sometimes amplify the double bounce
echo amplitude. Normally, double bounce echoes appear when the tank is
60-70% full. In these cases, the double bounce echo can cause the
transmitter to lock onto the wrong echo.
The Double Bounce function is used for managing problems with echoes
appearing in the tank because of the tank shape stronger than the surface
echo itself.
The Double Bounce Offset is given by the following formula:
Double Bounce Offset=B - 2*A,
where A is the distance from the Tank Reference Point to the product surface,
and B is the distance from the Tank Reference Point to the Double Bounce
echo. In many cases, the Double Bounce Offset is given by the height of the
nozzle.
Note that the surface echo is required to suppress the double bounce. If the
surface echo enters the hold off distance region, there is no product surface
reference and the double bounce might be interpreted as the surface echo.
A
B
Double Bounce Offset=B - 2*A
Amplitude
Dist
ance