Vaisala FD12P - Manual (Page 35)

Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 35
Cable Selection
Line Power Cabling
The FD12P is supplied with a two-meter power cable. If a local
terminal for 115/230 VAC power supply is not available, use an
extended mains cable from the FD12P to the nearest power source.
This cable should be armored and of underground type. The armored
reinforcing acts as a mechanical shield and also provides protection
against lightning. Ground the cable screen at both ends.
The recommended mains wire cross sections are shown in Table 5
below for mains voltage 230 VAC. For 115 VAC, divide the
maximum distances by four.
Table 5 Mains Cable Selection
Maximum
Distance from
Voltage Source One-wire
Cross-section
Area Nearest
AWG-gauge Typical Non-
armored Cable
Diameter
2 km 1.5 mm2 No 15 AWG 10 mm
4 km 2.5 mm2 No 13 AWG 14 mm
8 km 4.0 mm2 No 11 AWG 18 mm
NOTE Cables with diameters more than 12 mm require a separate junction
box which is also available from Vaisala.
Communication Cable
The FD12P provides the RS-232C, RS-485, CCITT V.21 modem, and
analog transmission interfaces. Consider your needs for
communication before the installation. The communication method
depends on the distance between the computer or display and the
FD12P and the number of the FD12P sensors. Table 6 below describes
the possibilities.
Table 6 Communication Cable Lengths
Cable Length One FD12P Several FD12Ps on line
< 150 m RS-232 RS-485, modem
< 500 m RS-485, modem RS-485, modem
> 500 m Modem Modem