VEGA VEGAFLEX 67 (-200…+400°C) 4 … 20 mA_HART four-wire - Manual (Page 9)

I t is designed for industrial use in all areas of process technology and
can be used in liquids.
H igh frequency microwave impulses are guided along a steel cable or
rod or a rod inside a steel tube. When reaching the product surface, a
part of the microwave impulses is reflected. The other part passes the
upper product and is reflected a second time by the interface. The
running times to the two product layers are processed by the
instrument.
Upper medium (L2)
l T he upper medium must not be conductive
l T
he dielectric figure of the upper medium must be known (input
required). Min. dielectric figure: rod version 1.7; coax version 1.4.
Y
ou can find a list with the dielectric figures on our home page:
www.vega.com
l T he composition of the upper medium must be stable, no varying
products or mixtures
l T he upper medium must be homogeneous, no stratifications within
the medium
l M in. thickness of the upper medium 100 mm
l C lear separation from the lower medium, no emulsion phase, no
mull layer
l I
f possible, no foam on the surface
Lower medium (L1)
l T he dielectric figure must be 10 higher than the dielectric figure of
the upper medium, preferably electrically conductive. Example:
upper medium dielectric figure 2, lower medium at least dielectric
fi
gure 12
Functional principle
Prerequisites for inter-
face measurement
VEGAFLEX 67 • 4 … 20 mA/HART - four-wire 9
3 P roduct description
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EN
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