User's Manual

BZ
Product zone
Antenna
minimum
ullage
Antenna
zone
length
Radar reference
AZ
SF
Threshold Product zone ZP
Antenna
surface
Antenna
min. ullage
Threshold
Bottom zone (ZB)
Bottom zone
offset BZ
Product zone
Antenna
zone length
AZ
Threshold
Antenna zone
ZA
Bottom zone
Ullage
Tank
zero
Radar reference
Signal
strength
[dB]
Bottom zone
0.44 m*
*) 3x Fourier distance
Commissioning
Instruction manual 973 SmartRadar LT Page 23
Warning
The product reflection in the area “Antenna minimum ullage” will be indicated as product level
with reduced accuracy and with warning code 7013: ‘level above measuring range’.
Do not use this area as normal operational area because of the chance for a tank overflow.
Figure 3.5 Zones and thresholds
3.4.4 Zones and threshold settings
The tank height is divided into 3 measuring zones: Antenna zone, Product zone and Bottom zone.
In addition, ten obstruction zones can be programmed. Refer to figure 3.5.
Please note that the X-axis from figure 3.5 indicates
ullage
. The zero point on the X-axis represents the
"Radar reference". This is in most cases the nozzle height, with respect to the tank zero, on which the
antenna is mounted (item
PR
; position radar). Refer also to figure 3.4.
The antenna is located inside the antenna minimum ullage area. In this area, reflections from the antenna
will decrease to almost zero at 0.5 to 2 metres distance from the antenna surface (depending on the type of
antenna).
Figure 3.6 shows a so-called reflection diagram.
The reflection diagram can be made with the Enraf service tool ”Ensite”.
Not all reflections in the reflection diagram are selected as possible peak for the product level. A first
selection can be made by the threshold in each of the three zones. The thresholds should be set such that
noise is filtered out. Only the peaks above a threshold setting are selected as possible product peak.
The antenna zone length (item
AZ
) covers the area where antenna reflections are low but still present.
The antenna zone threshold should cover the most of the antenna reflections.
The antenna zone length does not need to extend till the antenna reflections are completely zero; only
until the higher reflections are covered, such as those which might be expected in the product zone.
Refer to example of reflection diagram in figure 3.6.