1
M
easuring principle
1
.
1
O
verview
T
he
VEGABAR
81
,
82
and
83
can be used universally for the measure
-
ment of gases
,
vapours and liquids
.
T
he instrument series is designed for
all applications in industrial measurement engineering
.
T
he pressure
transmitters are the ideal solution for special as well as standard applica
-
tions
.
S
etup and commissioning is always the same
.
T
he
VEGABAR
81
,
82
and
83
o
ff
er maximum reliability and operational safety
.
1
.
2
M
easuring cell technology
VEGABAR
81
T
he
VEGABAR
81
is equipped with a chemical seal system
.
I
t consists of
a process diaphragm as well as an isolating liquid
.
T
he process dia
-
phragm is available in di
ff
erent materials
.
T
he process pressure acts on the sensor element via the chemical seal
system and an internal stainless steel diaphragm
.
T
he process pressure
causes a resistance change which is converted into a corresponding
output signal and outputted as measured value
.
1
3
4
2
F
ig
.
1
:
C
on
fi
guration of the piezoresistive measuring cell in
VEGABAR
81
1
S
ensor element
2
B
ase element
3
S
ilicone oil
fi
lling
4
P
rocess diaphragm
F
or 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
T
he sensor element is the
CERTEC
®
measuring cell with front
-
fl
ush
,
abrasion resistant ceramic diaphragm
.
T
he hydrostatic pressure of the
medium or the process pressure causes a capacitance change in the
measuring cell via the diaphragm
.
T
his change is converted into an ap
-
propriate output signal
.
16 µm
1
2
3
F
ig
.
2
:
C
on
fi
guration of the
CERTEC
®
measuring cell in
VEGABAR
82
1
D
iaphragm
2
S
oldered glass bond
3
B
ase element
T
he
CERTEC
®
measuring cell is also equipped with a temperature sen
-
sor
.
T
he temperature value can be displayed via the display and adjust
-
ment module or processed via the signal output
.
VEGABAR
83
T
he process pressure acts via the process diaphragm to the sensor ele
-
ment
.
T
he process pressure causes a resistance change which is con
-
verted into a corresponding output signal and outputted as measured
value
.
T
he process diaphragm is available in di
ff
erent materials
.
F
or 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
.
W
ith small measuring ranges or higher temperatures
,
the
METEC
®
measuring cell is used
.
I
t consists of the ceramic
-
capacitive
CERTEC
®
measuring cell and a special
,
temperature
-
compensated chemical seal
system
.
4
3
2
1
F
ig
.
3
:
C
on
fi
guration of the
METEC
®
measuring cell in
VEGABAR
83
1
P
rocess diaphragm
2
I
solating liquid
3
F
e
N
i adapter
4
CERTEC
®
measuring cell
M
easuring principle
P
rocess pressure
–
P
ressure transmitter
3
45078
-
EN
-
140625
