Technical information

7500 RTG
6 Varec, Inc.
Measuring Conditions
• The measuring range begins where the beam hits
the tank bottom. Particularly with dish bottoms or
conical outlets the level cannot be detected below
this point.
•For overspill protection, it is possible to define a
safety distance (SD) additionally to the blocking
distance (BD).
• Depending on its consistence, foam can either
absorb microwaves or reflect them off the foam
surface. Measurement is possible under certain
conditions.
• Distance B defined the smallest recommended
measurement range.
• Tank diameter and height should be at least
dimensioned such that a reflection of the radar
signal on both sides of the tank can be ruled out.
• 7530 RTG, 7531 RTG, 7533 RTG: In case of media
with a low dielectric constant (groups A and B), the
tank bottom can be visible through the medium at
low levels (low height C). Reduced accuracy has to be
expected in this range. If this is not acceptable, we
recommend positioning the zero point at a distance
C above the tank bottom in these applications.
7532 RTG: The zero should be positioned at the end
of the tube, as the electromagnetic waves do not
propagate completely outside the tube. It must be
taken into account that the accuracy may be reduced
in the area C. In order to guarantee the required
accuracy in these cases, it is recommended to
position the zero-point at a distance C above the
tank bottom.
• In principle it is possible to measure up to the tip of
the rod and horn antenna. However, due to
considerations regarding accuracy corrosion and
build-up, the end of the measuring range should not
be chosen any closer than 50 mm (2”) to the tip of
the rod and horn antenna.
• In applications with planar or parabolic antennas,
especially for media with low dielectric constants,
the end of the measuring range should not be closer
than 1 m (40”) to the flange.
• This safety distance (SD) is set to 0.1 m (4") by
default for 7530 RTG (horna antenna) and 7531 RTG
(rod antenna) and generating an alarm in case the
product level rises inside the safety distance.
• For 7533 RTG (parabolic antenna) and 7532 RTG
(planar antenna) the safety distance (SD) is set to 0.5
m (20") by default, generating an alarm in case the
product level rises inside the safety distance.
Measuring Conditions & Gauge Orientation
A
100%
0%
B
BD
BD
SD
SD
A
100%
0%
B
C
FMR530/531/533 FMR532
C
ØD
max. levelmax. level
reference: flange / BD (cf. picture) reference: antenna tip (cf. picture)
Blocking distance Safety distance recommended additional settings
BD [m / ft] SD [m / ft] A [mm / inch] B [m / ft] C [mm / inch]
7530 RTG (horn)
horn length 0.1 / 0.3 50 / 2 0.5 / 1.6 150…300 / 6…12
7531 RTG (rod)
0.39/1.3 or 0.54/1.8 0.1 / 0.3 50 / 2 0.5 / 1.6 150…300 / 6…12
7532 RTG (planar)
1 / 3.28" 0.5 / 1.6 1000 / 40 0.5 / 1.6 150…300 / 6…12
7533 RTG (parabolic)
1 / 3.28 0.5 / 1.6 1000 / 40 0.5 / 1.6 150…300 / 6…12