5
C
onnecting to power supply
5
.
1
P
reparing the connection
A
lways keep in mind the following safety instructions
:
l
C
onnect only in the complete absence of line voltage
l
I
f overvoltage surges are expected
,
overvoltage arresters should
be installed according to
F
oundation
F
ieldbus speci
fi
cation
T
ip
:
W
e recommend
VEGA
overvoltage arrester
B
63
-
32
.
I
n hazardous areas you must take note of the respective regulations
,
conformity and type approval certi
fi
cates of the sensors and power
supply units
.
T
he instrument requires a operating voltage of
9
…
32
V DC
.
O
perating voltage and the digital bus signal are carried on the same
two
-
wire connection cable
.
P
ower is supplied via the
H
1
power supply
.
C
onnection is carried out with screened cable according to
F
ieldbus
speci
fi
cation
.
U
se cable with round cross
-
section
.
A
cable outer diameter of
5
…
9
mm
(
0
.
2
…
0
.
35
in
)
ensures the seal e
ff
ect of the cable gland
.
I
f you are
using cable with a di
ff
erent diameter or cross
-
section
,
exchange the
seal or use a suitable cable gland
.
M
ake sure that the entire installation is carried out according to the
F
ieldbus speci
fi
cation
.
I
n particular
,
make sure that the bus is
terminated with suitable terminating resistors
.
O
n the instrument with cable entry
½
NPT
and plastic housing there is
a metallic
½"
threaded insert moulded into the plastic housing
.
C
aution
:
N
o grease should be used when screwing the
NPT
cable gland or
steel tube into the threaded insert
.
S
tandard grease can contain
additives that corrode the connection between threaded insert and
housing
.
T
his would in
fl
uence the stability of the connection and the
tightness of the housing
.
I
n systems with potential equalisation
,
connect the cable screen
directly to ground potential at the power supply unit
,
in the connection
box and at the sensor
.
T
he screen in the sensor must be connected
directly to the internal ground terminal
.
T
he ground terminal outside on
the housing must be connected to the potential equalisation
(
low
impedance
).
S
afety instructions
V
oltage supply
C
onnection cable
C
able gland
½
NPT
C
able screening and
grounding
18
VEGABAR
51
•
F
oundation
F
ieldbus
5
C
onnecting to power supply
36715
-
EN
-
110629
