Vega VEGADIF 65 Operating Instructions Manual page 11

Functional principle
Voltage supply
VEGADIF 65 • 4 ... 20 mA
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:
Fig. 8: Metallic measuring cell 10 mbar and 30 mbar - p
sures
1 Measuring element
2 Silicone diaphragm
3 Separating diaphragm
4 Filling oil
5 Integrated overvoltage arrester
p
1
Fig. 9: Metallic measuring cell from 100 mbar - p
1 Measuring element
2 Overload diaphragm/Middle diaphragm
3 Filling oil
4 Separating diaphragm
4 ... 20 mA two-wire electronics for voltage supply and measured
value transmission on the same cable.
The supply voltage range can differ depending on the instrument ver-
sion. The exact range is stated in chapter "Technical data".
The backlight of the display and adjustment module is powered by
the sensor. The prerequisite for this is a supply voltage at a certain
p
1
1
3 Product description
1
2
3
p
4
2
5
and p process pres-
1 2
2
3
p
2
4
and p process pressures
1 2
11