VEGA VEGABAR 82 4 … 20 mA_HART - Operating Instructions - Manual (Page 9)

9
3 Product description
VEGABAR 82 • 4 … 20 mA/HART
45028-EN-131010
•
Absolute pressure
•
Vacuum
Measured products are gases, vapours and liquids.
Depending on the process fitting and measurement setup, measured
products can be also viscous or contain abrasive substances.
Sensor element is the CERTEC ® measuring cell with robust ceramic
diaphragm. The process pressure deflects the ceramic diaphragm
and causes a capacitance change in the measuring cell. This capaci-
tance change is converted into an electrical signal and outputted as
measured value via the output signal.
The CERTEC
® measuring cell is available in two sizes:
•
ø 17.5 mm with small process fittings and pressure measuring
range 100 bar
•
ø 28 mm with large process fittings as well as all flange connec-
tions
The CERTEC ® measuring cell has also an integrated temperature
sensor. The temperature value is outputted through:
•
The display and adjustment module
•
The current output
•
The digital signal output
The measuring cell design depends on the selected pressure type.
Relative pressure: the measuring cell is open to atmosphere. The
ambient pressure is detected in the measuring cell and compensated.
It thus has no influence on the measured value.
Absolute pressure: the measuring cell is evacuated and encapsu-
lated. The ambient pressure is not compensated and does hence
influence the measured value.
Relative pressure, climate-compensated: the measuring cell is
evacuated and encapsulated. The ambient pressure is detected
through a reference sensor in the electronics and compensated. It
thus has no influence on the measured value.
The following presentations show the installation of the CERTEC ®
measuring cell into the process fitting and the different seal concepts.
Measured products
Measuring system
Pressure types
Seal concepts