Vega VEGABAR 81 Product Information - page 3
1
Measuring principle
1
.1
Overview
The VEGABAR 81, 82 and 83 can be used universally for the measure-
ment of gases, vapours and liquids. The instrument series is designed for
all applications in industrial measurement engineering. The pressure
transmitters are the ideal solution for special as well as standard applica-
tions. Setup and commissioning is always the same. The VEGABAR 81,
82 and 83 offer maximum reliability and operational safety.
1
.2
Measuring cell technology
VEGABAR 81
The VEGABAR 81 is equipped with a chemical seal system. It consists of
a process diaphragm as well as an isolating liquid. The process dia-
phragm is available in different materials.
The process pressure acts on the sensor element via the chemical seal
system and an internal stainless steel diaphragm. The process pressure
causes a resistance change which is converted into a corresponding
output signal and outputted as measured value.
1
3
4
2
Fig. 1: Configuration of the piezoresistive measuring cell in VEGABAR 81
1
Sensor element
2
Base element
3
Silicone oil filling
4
Process diaphragm
For measuring ranges up to 40 bar, a piezoresistive sensor element with
internal transmission liquid is used, and for measuring ranges 100 bar and
higher, a strain gauge (DMS) sensor element on the back side of the
stainless steel diaphragm (dry) is used.
VEGABAR 82
The sensor element is the CERTEC
®
measuring cell with front-flush,
abrasion resistant ceramic diaphragm. The hydrostatic pressure of the
medium or the process pressure causes a capacitance change in the
measuring cell via the diaphragm. This change is converted into an ap-
propriate output signal.
16 µm
1
2
3
Fig. 2: Configuration of the CERTEC
®
measuring cell in VEGABAR 82
1
Diaphragm
2
Soldered glass bond
3
Base element
The CERTEC
®
measuring cell is also equipped with a temperature sen-
sor. The temperature value can be displayed via the display and adjust-
ment module or processed via the signal output.
VEGABAR 83
The process pressure acts via the process diaphragm to the sensor ele-
ment. The process pressure causes a resistance change which is con-
verted into a corresponding output signal and outputted as measured
value. The process diaphragm is available in different materials.
For measuring ranges up to 40 bar, a piezoresistive sensor element with
internal transmission liquid is used, and for measuring ranges 100 bar and
higher, a strain gauge (DMS) sensor element on the back side of the
stainless steel diaphragm (dry) is used.
With small measuring ranges or higher temperatures, the METEC
®
measuring cell is used. It consists of the ceramic-capacitive CERTEC
®
measuring cell and a special, temperature-compensated chemical seal
system.
4
3
2
1
Fig. 3: Configuration of the METEC
®
measuring cell in VEGABAR 83
1
Process diaphragm
2
Isolating liquid
3
FeNi adapter
4
CERTEC
®
measuring cell
Measuring principle
Process pressure – Pressure transmitter
3
45078
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EN
-140625