VEGA VEGABAR 86 4 … 20 mA - Operating Instructions - Manual (Page 9)

9
3 Product description
VEGABAR 86 • 4 … 20 mA
45506-EN-131010
through different cable and tube versions allows the instrument to be
used in many different applications.
Measured products are liquids.
Depending on the instrument version and measurement setuo, meas-
ured 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 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 illustration shows the installation of the CERTEC ®
measuring cell in the transmitter as well as the sealing concept.
1
2
3
4
5
Fig. 3: Front-flush installation of the CERTEC ® measuring cell with double seal
1 Housing, transmitter
2 Measuring cell
3 Lateral seal for measuring cell
4 Additional, front seal for measuring cell
5 Diaphragm
Measured products
Measuring system
Pressure types
Seal concept