VEGA VEGABAR 87 Profibus PA - Operating Instructions - Manual (Page 9)

9
3 Product description
VEGABAR 87 • Profibus PA
45047-EN-131107
The VEGABAR 87 is a pressure transmitter for pressure and level
measurements of liquids with higher temperatures in the chemical,
food processing and pharmaceutical industry.
Measured products are liquids.
Depending on the instrument version and the measurement setup,
the measured products can be also viscous.
The process pressure acts on the sensor element via the stainless
steel diaphragm and an internal transmission liquid. The process
pressure causes a resistance change which is converted into a cor-
responding output signal and outputted as measured value.
The METEC
® measuring cell is the measuring unit. It consists of
the ceramic-capacitive CERTEC ® measuring cell and a special,
temperature-compensated isolating system.
4 3 2 1
Fig. 3: Configuration of the METEC ® measuring cell with VEGABAR 87
1 Process diaphragm
2 Isolating liquid
3 FeNi adapter
4 CERTEC ® measuring cell
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.
Application area
Measured products
Measuring system
Pressure types
Seal concept