VEGA VEGAFLEX 81 Foundation Fieldbus Coax probe - Manual (Page 12)

12
3 Product description
VEGAFLEX 81 • Foundation Fieldbus
44215-EN-130910
TS
d1
h1
h2
d2
1
L2
L1
L3
Fig. 5: Interface measurement
1 Sensor reference plane (seal surface of the process fitting)
d1 Distance to the interface
d2 Distance to the level
TS Thickness of the upper medium (d1 - d2)
h1 Height - Interface
h2 Height - Level
L1 Lower medium
L2 Upper medium
L3 Gas phase
Upper medium (L2)
•
The upper medium must not be conductive
•
The dielectric constant of the upper medium or the actual distance
to the interface must be known (input required). Min. dielectric con-
stant: 1.6. You can find a list of dielectric constants on our home
page: www.vega.com.
•
The composition of the upper medium must be stable, no varying
products or mixtures
•
The upper medium must be homogeneous, no stratifications
within the medium
•
Min. thickness of the upper medium 50 mm (1.97 in)
•
Clear separation from the lower medium, emulsion phase or detri-
tus layer max. 50 mm (1.97 in)
•
If possible, no foam on the surface
Lower medium (L1)
•
The dielectric constant must be 10 higher than the dielectric
constant of the upper medium, preferably electrically conductive.
Example: upper medium dielectric constant 2, lower medium at
least dielectric constant 12.
Gas phase (L3)
•
Air or gas mixture
•
Gas phase - dependent on the application, gas pahse does not
always exist (d2 = 0)
Prerequisites for inter-
face measurement