User Manual

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 ÜS-F-LB-I
and ÜSB 62-36G.X.
In hazardous areas you should take note of the
appropriate regulations, conformity and type approval
certificates of the sensors and power supply units.
Power supply and current signal are transmitted via the
same two-wire connection cable. The power supply
range can differ depending on the instrument version.
The exact range is stated in the Technical data in the
Supplement.
Provide a reliable separation between the supply circuit
and the mains circuits acc. to DIN VDE 0106 part 101.
The VEGA power supply units VEGATRENN 149AEx,
VEGASTAB 690, VEGADIS 371 as well as all VEGA-
METs meet this requirement.
Bear in mind the following factors regarding supply
voltage:
l the reduction of the output voltage of the power
supply unit under nominal load (with a sensor current
of 20.5 mA or 22 mA in case of fault signal)
l the influence of additional instruments in the circuit
(see load values in Technical data)
VEGAPULS 68 is connected with standard two-wire
cable without screen. A n outer cable diameter of 5 ...
9 mm ensures the seal effect of the cable entry. If
electromagnetic interference is expected, we recom-
mend the use of screened cable.
Note safety instructions
Take note of safety
instructions for Ex
applications
Select power supply
Select connection cable
22 VEGAPULS 68 - 4 ... 20 mA/HART
Connecting to power supply
29261-EN-050202