Operating instructions

5 Connecting to power supply
5.1 Preparing the connection
Always observe the following safety instructions:
l Connect only in the complete absence of line voltage
l If overvoltages are expected, overvoltage arresters should
be installed.
Tip:
We recommend VEGA overvoltage arresters B61-300 (power
supply VEGAMET 625) and B62-36G (sensor supply).
In hazardous areas you should take note of the appropriate
regulations, conformity and type approval certificates of the
sensors and power supply units.
The power supply can be 20 … 253 VAC, 50/60 Hz.
Power supply of VEGAMET 625 is connected with standard
cable acc. to the national installation standards.
Standard two-wire cable with screening can be used for
connecting the sensors. The screening is absolutely neces-
sary to ensure interference-free operation with HART sensors.
Connect the cable screen on both ends to ground potential. In
the sensor, the screen must be connected directly to the
internal ground terminal. The ground terminal outside on the
sensor housing must be connected to the potential equalisa-
tion.
If potential equalisation currents are expected, the screen
connection on VEGAMET 625 must be made via a ceramic
capacitor (e.g. 1 nF, 1500 V). The low frequency potential
equalisation currents are thus suppressed, but the protective
effect against high frequency interference signals remains.
Take note of the corresponding installation regulations for Ex
applications. In particular, make sure that no potential
equalisation currents flow over the cable screen. In case of
grounding on both sides this can be achieved by the use of a
capacitor or a separate potential equalisation.
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Select connection cable
Cable screening and groun-
ding
Select connection
cable for Ex applica-
tions
12 VEGAMET 625 - Double channel Hart signal conditioning instrument
Connecting to power supply
28970-EN-050616