The 25 mm long threaded socket should
project into the silo so as to minimise
effects due to condensation and
material build-up.
★
L
B
(covered length):
With non-conductive materials having
low dielectric constants, the rope probe
must be approx. 5 % (or minimum
300 mm) longer than the distance from
the roof of the vessel to the switch point.
If it is not possible to select the correct
L
B
for minimum detection with very long
Heat insulation prevents condensation
and build-up on the steel plate.
When mounting in a silo made of
plastic, a counter electrode must be
mounted on the outside and at the same
height as the weight.
The length of the edge of the counter
electrode should be roughly the same
length as the distance of the weight to
the silo wall.
probes then a special version with
»butterfly weight« can be supplied as
an accessory. The increased surface
area of this weight ensures that there is
a large enough change in capacitance
when the probe is covered by material.
An L
B
of 300 mm is normally sufficient.
TI133Y09
Steel plate
connected to
the reinforcing
steel
Concrete
roof
recommended
with
condensation:
Heat
insulation
Steel plate
Silo with concrete walls
TI133Y10
Ground
connection
Surface
area
e.g. 1 m
2
Counter
electrode e.g.
sheet metal plate
Weight
Electrical
HF field
Distance
e.g. 1 m
TI133Y11
L
Limit
Electrically
conductive bulk
solid (e.g. ore)
L
Limit
L
B
m
in.
200 mm
Bulk solid with high
dielectric constant
(e.g. meal)
L
mi
n.
0.05x
L
mi
n.
300 m
m
L
B
★
Bulk solid with low
dielectric constant
(e.g. moulding sand)
Limit
Silo with plastic walls
Different probe lengths
8
