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 overvoltages are expected
,
install overvoltage arresters
I
n hazardous areas you should take note of the appropriate
regulations
,
conformity and type approval certi
fi
cates of the sensors
and power supply units
.
T
he voltage supply can be
20
…
253
V AC
/
DC
,
50
/
60
H
z
.
T
he operating voltage of
VEGAMET
624
is connected with standard
cable according to the national installation standards
.
S
tandard two
-
wire cable can be used for connecting the sensors
.
T
he
screening is absolutely necessary to ensure interference
-
free oper
-
ation with
HART
sensors
.
C
onnect the cable screen on both ends to ground potential
.
I
n the
sensor
,
the screen must be connected directly to the internal ground
terminal
.
T
he ground terminal on the outside of the sensor housing
must be connected to the potential equalisation
(
low impedance
).
I
f potential equalisation currents are expected
,
the screen connection
on the side of
VEGAMET
624
must be made via a ceramic capacitor
(
e
.
g
.
1
n
F
,
1500
V
).
T
he low frequency potential equalisation currents
are thus suppressed
,
but the protective e
ff
ect against high frequency
interference signals remains
.
T
ake note of the corresponding installation regulations for
E
x
applications
.
I
n particular
,
make sure that no potential equalisation
currents
fl
ow over the cable screen
.
I
n case of grounding on both sides
this can be achieved by the use of a capacitor or a separate potential
equalisation
.
5
.
2
C
onnection procedure
M
ove on to electrical connection and proceed as follows
:
1
S
nap the socket without
VEGAMET
624
onto the carrier rail
2
C
onnect sensor cable to terminal
1
/
2
(
active input
)
or
3
/
4
(
passive
input
),
provide a screening
3
W
hen using several sockets
,
loop the power supply by means of
bridges
4
C
onnect power supply
(
switched o
ff
)
to terminal
17
and
18
5
I
f necessary
,
connect relays or other outputs
N
ote safety instructions
T
ake note of sa
-
fety instructions
for
E
x applica
-
tions
S
elect power supply
S
electing connection
cable
C
able screening and
grounding
S
elect connec
-
tion cable for
E
x
applications
12
VEGAMET
624
•
4
…
20
m
A
/
HART
signal conditioning instrument
5
C
onnecting to power supply
28969
-
EN
-
091116
