VEGA POINTRAC 31 8_16 mA_HART - four-wire - Manual (Page 16)

16
5 Connecting to power supply
POINTRAC 31 • 8/16 mA/HART - four-wire
39411-EN-131119
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
•
Connect only in the complete absence of line voltage
•
If overvoltage surges are expected, overvoltage arresters should
be installed
In this case, the instrument is designed in protection class II. To main-
tain this protection class, it is absolutely necessary that the ground
conductor be connected to the internal ground terminal. Take note of
the general installation regulations.
Supply voltage and current signal are carried on separate connection
cables if reliable separation is required. The supply voltage range can
differ depending on the instrument version.
The data for power supply are specified in chapter "Technical data".
For power supply, an approved installation cable with PE conductor is
required.
The 8/16 mA current output is connected with standard two-wire ca-
ble without screen. If electromagnetic interference is expected which
is above the test values of EN 61326 for industrial areas, screened
cable should be used.
Use cable with a round wire cross section. An outer cable diameter
of 6 … 12 mm (0.24 … 0.47 in) ensures the seal effect of the cable
entry. If cable with a different diameter or wire cross section is used,
exchange the seal or use an appropriate cable connection. Unused
cable entry glands do not provide sufficient protection against mois-
ture and must be replaced with blind plugs.
Generally provide all unused cable entries with suitable blind plugs.
The thin foam rubber washers in the cable glands only serve as a
dust cover during transport.
In the case of instrument housings with self-sealing NPT threads, it
is generally not possible to have the cable glands screwed in at the
factory. The openings for the cable glands are therefore covered with
red protective caps as transport protection.
Before setup you have to replace these protective caps with approved
cable glands or close the openings with suitable blind plugs. Unused
cable glands do not provide sufficient protection against moisture and
must be replaced with blind plugs.
The suitable cable glands and blind plugs come with the instrument.
If screened cable is necessary, 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 on the
outside of the housing must be connected to the potential equalisa-
tion (low impedance).
Safety instructions
Voltage supply via mains
voltage
Select connection cable
Cable entry
Cable gland ½ NPT
Cable screening and
grounding