VEGA VEGADIF 65 Profibus PA - Manual (Page 11)

11
3 Product description
VEGADIF 65 • Profibus PA
36129-EN-130417
A metallic measuring cell is used as sensor element. The process
pressures are transmitted via the separating diaphragms and filling
oils to a resistance measuring bridge (semi-conductor technology).
The difference between the acting pressures generates a change in
the bridge voltage. This change is measured, further processed and
converted into a corresponding output signal.
The markings "+" and "-" on the process component in chapter
"Mounting and connection instructions" must therefore be noted when
connecting to the process. The pressure acting on "+" goes positive,
the pressure acting on "-" goes negative into the calculation of the
pressure difference.
The configuration of the measuring cells differs depending on the
measuring range:
1
2
3
4
5
1
p
2
p
Fig. 8: Metallic measuring cell 10 mbar and 30 mbar - p
1
and p
2
process pres-
sures
1 Measuring element
2 Silicone diaphragm
3 Separating diaphragm
4 Filling oil
5 Integrated overvoltage arrester
1
p
2
p
1
2
3
4
Fig. 9: Metallic measuring cell from 100 mbar - p
1
and p
2
process pressures
1 Measuring element
2 Overload diaphragm/Middle diaphragm
3 Filling oil
4 Separating diaphragm
Power supply via the Profibus DP/PA segment coupler or VEGALOG
571 EP cards. A two-wire cable according to Profibus specification
serves as carrier of both power and digital data transmission for
multiple sensors. The instrument profile of VEGADIF 65 corresponds
to profile specification version 3.0.
Functional principle
Power supply and bus
communication