159
Reference Manual
00809-0100-4530, Rev DD
May 2016
7.4
Product surface peak not found
The amplitude of the measurement signal, i.e. the amplitude of the signal that is reflected
by the product surface, is related to the actual dielectric constant of the product. The
amplitude threshold that is used by the transmitter is based on the parameter configuration
of the current product dielectric constant (see section
“Basic configuration parameters” on
). Normally no other threshold adjustment is needed, but if the transmitter still
does not track the product surface correctly, it may be necessary to adjust the threshold
values.
Rosemount Radar Master (RRM) has a plot function showing the reflections along the probe
(see
“Using the echo curve analyzer” on page 153
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 has to be lowered so that the
Surface peak is not filtered out.
Figure 7-6. Surface Threshold is Too High
If there are disturbing objects in the tank, the threshold must be carefully set to avoid
locking on the wrong amplitude peak. In
, the transmitter has locked on a peak
above the actual product surface, i.e. a disturbance was interpreted as the product surface,
whereas the actual product surface was interpreted as the interface or the probe end.
Figure 7-7. Surface Threshold is Too Low
3.0
5.0
The Surface Threshold is above
the Surface peak
Surface Threshold=
Amplitude Threshold
Curve (ATC)
Reference Threshold
Amplit
ude
, mV
Distance, m
3.0
5.0
Actual surface
Disturbing
echo
misinterpreted
as product
surface
Amplitude
, m
V
Distance, m
Reference Threshold
Surface Threshold=
Amplitude Threshold
Curve (ATC)