Rosemount 5401, Reference Manual

Page: 97 / 180

Reference Manual
00809-0100-4026, Rev FA
July 2009
7-7
Rosemount 5400 Series
Registration of False
Echoes
The False Echo function improves the performance of the gauge when the
surface is close to a horizontal surface of a static 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 may interfere and cause a
decrease in performance.
Figure 7-5. The Rosemount
5400 can handle disturbing
radar echoes.
The False Echo function allows registration of disturbing echoes caused by
objects in the tank. When the surface is passing a disturbing object, the
transmitter measures with higher reliability if 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.
Follow these recommendations before registering new interfering echoes:
• Make sure a correct amplitude threshold curve is set before registering
any disturbance echoes (see “Amplitude Threshold Curve” on
page 5-11)
• Compare the list of interfering echoes with the tank drawing or visual
inspection of the tank. Note any objects like beams, heating coils,
agitators, etc. which correspond to the found echoes. Only register
echoes above the Amplitude Threshold Curve which can be clearly
identified as objects in the tank, keeping the number of registered
echoes to a minimum
• Make sure the level is stable before registering a disturbance echo. A
fluctuating level may indicate a temporary disturbance that is not from
an interfering object
• Do not register False Echoes located below the product surface. It is
recommended that registration be done when the tank is empty
False echo
Surface echo
Disturbing
objects