VEGA VEGAFLEX 67 (-200…+400°C) Foundation Fieldbus - Manual (Page 9)

It is designed for industrial use in all areas of process technology and
can be used in liquids.
High 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 The upper medium must not be conductive
l The dielectric figure of the upper medium must be known (input
required). Min. dielectric figure: rod version 1.7; coax version 1.4.
You can find a list with the dielectric figures on our home page:
www.vega.com
l The composition of the upper medium must be stable, no varying
products or mixtures
l The upper medium must be homogeneous, no stratifications within
the medium
l Min. thickness of the upper medium 100 mm
l Clear separation from the lower medium, no emulsion phase, no
mull layer
l If possible, no foam on the surface
Lower medium (L1)
l The 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
figure 12
Functional principle
Prerequisites for inter-
face measurement
VEGAFLEX 67 • Foundation Fieldbus 9
3 Product description
32314
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EN
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