VEGA VEGADIF 65 4 … 20 mA_HART - Manual (Page 11)

11
3 Product description
VEGADIF 65 • 4 … 20 mA/HART
36128-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
4 … 20 mA/HART two-wire electronics for voltage supply and meas-
ured value transmission on the same cable.
The supply voltage range can differ depending on the instrument
version.
The data for power supply are specified in chapter "Technical data".
Functional principle
Voltage supply