Echo Tuning; Registration Of False Echoes - Emerson Rosemount 5400 Series Reference Manual

Preliminary copy
Rosemount 5400 Series

ECHO TUNING

Registration of False
Echoes
Figure 5-3.
5-8
There are different methods available for disturbance echo handling with the
Rosemount 5400 Series Transmitter:
• False Echo registration
• Customized Noise Threshold Table (Amplitude Threshold Curve (ATC)
The False Echo function is used to improve the performance of the gauge
when the surface is close to a horizontal surface of a stationary object in the
tank. The object causes an echo when it is above the surface. When the
echoes from the surface and the object are close to each other, they might
interfere and cause a decrease in performance.
False echo
Surface echo
The False Echo function allows you to register disturbing echoes caused by
objects in the tank in the memory of the gauge. When the surface is passing
by a disturbing object, the gauge can measure with a higher reliability, when
the position of the object is registered. This makes it possible to detect a
product surface close to a disturbance echo even if the surface echo is
weaker than the disturbing echo. See the following recommendations before
you register new interfering echoes:
• Make sure that a correct amplitude threshold is set before you register
any disturbance echoes.
• Keep the number of registered echoes to a minimum.
• Compare the list of interfering echoes with the tank drawing or by
visible inspection of the tank. Note if there are objects like beams,
heating coils, agitators etc. which correspond to the found echoes. Only
register echoes which can be clearly identified as objects in the tank.
• Make sure that the level is stable before you register a disturbance
echo. A fluctuating level may indicate a temporary disturbance which is
not due to an interfering object.
Reference Manual
00809-0100-4026, Rev AA
November 2003
Disturbing
object