Vega VEGADIF 65 Operating Instructions Manual page 29

Interface measurement
VEGADIF 65 • Foundation Fieldbus
The min. adjustment is carried out for the differential pressure
measured at density 1.0:
Δp = • g • h
= 1.0 kg/dm³ • 9.81m/s • 0.3 m
= 29.4 mbar
The max. adjustment is carried out for the differential pressure
measured at density 1.2:
Δp = • g • h
= 1.2 kg/dm³ • 9.81m/s • 0.3 m
= 35.3 mbar
Fig. 23: Measurement setup with density measurement
In a vessel with varying level, an interface measurement with a
differential pressure transmitter can be realized. The connection on the
vessel is carried out via a chemical seal on two measuring points. An
interface measurement is only possible if the densities of the two
products remain the same and the interface is always between the two
measuring points. The total level must always be above the upper
measuring point.
This density measurement functions with open but also with closed
vessel.
Example for an interface measurement:
Distance between the two measurement points: 0.3 m
Min. density: 0.8 kg/dm
Max. density: 1.0 kg/dm
The min. adjustment is carried out for the differential pressure occuring
with density 0.8:
Δp = • g • h
= 0.8 kg/dm³ • 9.81 m/s• 0.3 m
∆p
–
=
h g
+
3
3
4 Mounting
29