Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 25
Cable Selection
This section describes the power and signal cabling of FS11 Visibility
Sensor. The customer is responsible for supplying the power and signal
cables, and conduits for the cables. In all field cabling, the following
should be remembered:
- Use armored field cables.
- Cables must be suitable for underground use.
- Check the cable core diameter according to maximum allowable drop,
refer to Table 6 on page 27 for examples.
- Lead the cables to the equipment through conduits.
- Ground the cable shield at both ends.
- Use overvoltage protection devices in both ends of the field cables.
It is recommended to protect the cables by putting a brightly colored,
warning plastic tape into the ground about 0.5 m above the cables and
0.2 m below the ground level.
Armored tube or similar should be used to mechanically protect the AC
cable and the signal cable from the termination box down into the ground
(0.7 m below the ground).
This equipment is designed for continuous 24-hour operation. The AC
power supply should be continuous and without surges or blackouts. If
the AC voltage fluctuates outside the given tolerance, AC voltage
stabilizers are recommended.
Line Power Cable
FS11 is supplied with a 3-m power cable with free wire ends. If a local
terminal with the power supply of 115/230 VAC is not available, an
extended AC (mains) cable from FS11 to the nearest power source is
needed. This cable must be armored and suitable for underground use.
The armored reinforcing acts as a mechanical shield and also provides
protection against lightning. The cable screen must be grounded at both
ends.
NOTE
A separate junction box, where the extended AC (mains) cable is
terminated, is highly recommended at the installation site. A junction
box that fits inside the FS11 radiation shield is available from Vaisala.
See Figure 4 on page 26. This junction box also contains extra lightning
protection, which is recommended at sites where thunderstorms are
common.
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