Surface Pulse Not Found - Emerson Rosemount 5402 Reference Manual

Reference Manual
00809-0100-4026, Rev KC
Hold off distance - upper null zone. Measurements are not performed within the hold off distance. By
setting the hold off distance to zero, measurements can be performed close to the flange. Consider near
zone accuracy. See
Tank bottom. Measurements are not performed after the Tank Bottom limit.
7.3.2

Surface pulse not found

The amplitude thresholds are adjusted manually or during the Measure and Learn function to appropriate
values to filter out noise and other non-valid measurements from the measurement signal.
The amplitude of the measurement signal, that is the amplitude of the signal reflected by the product
surface, is related to the actual dielectric constant of the product.
RRM has a plot function that allows viewing of the reflections in the tank.
If the amplitude threshold is too high, the product level will not be detected, as illustrated in
In a situation like this, the amplitude threshold is lowered so the Surface peak is not filtered out.
Figure 7-2. Example 1: Surface Threshold is Too High
If there are disturbing objects in the tank, the threshold must be set carefully to avoid locking on the
wrong amplitude peak. In
surface, that is a disturbance was interpreted as the product surface.
Figure 7-3. Example 2: Surface Threshold is Too Low
Service and Troubleshooting
"Near zone distance and accuracy" on page
Reference
Figure 7-3, the transmitter has locked on a peak above the actual product
Reference
Distance, m
217.
The surface threshold is above
the surface peak
Distance, m
Actual surface
Service and Troubleshooting
October 2018
Surface threshold =
ATC
P1 - Disturbing echo
misinterpreted as
product surface
Surface threshold =
ATC
Figure 7-2.
163