Mettler Toledo IND780 Manual De Instalación página 56

IND780 Installation Manual
When the terminal is used with cable lengths exceeding those given above or with
more than 14 PDX cells, it is recommended to install the optional external 24 VDC
power supply (P/N 0917-0240). With the external supply, it is possible to use up
to 24 load cells per terminal, a maximum home run cable length of 300 m (984
ft) and a total of 200 m (656 ft) of cell-to-cell cable. The external power supply is
connected to pins 9 and 10 on the PDX board.
Home Run Cable Grounding and Shielding
Ground and shield terminations are a critical part of the system's immunity to
noise and electrical surges. To prepare for the terminations on the home run cable:
1. Cut and remove an appropriate length of the outer braid shield and the
insulation sheath, ensuring that there is sufficient length to provide strain relief
for the connection of the wires to the option board.
2. Trim the inner braid shield and the foil, leaving about 20 mm (0.8 inches)
exposed.
3. When installing an IND780 harsh enclosure terminal:
a. Install the cable gland assembly, metal clamp and the brass sleeve onto
b. Fold and spread out the inner braid shield and foil over the metal ring
Outer braid
Clamp
Insulation sheath
c. Pull the outer braid forward to cover the brass sleeve and wrap one end of
2-28
the home run cable while sliding back the outer braid shield (Figure
2-43). The inner drain wire should go into the enclosure through the cable
gland, while the outer drain wire remains on the outside.
before pressing the grommet into the body of the cable gland, as shown in
Figure 2-43. Tighten the cable gland's nut with the brass sleeve onto the
body of the gland.
Outer drain wire
Brass sleeve
Gland nut
Figure 2-43: PDX Home Run Cable and Gland Assembly
a flat braided ground cable over it before securing everything down using
the metal clamp (Figure 2-44). Route the home run cable's outer drain
wire along with the flat braided cable through a ground lug attached to the
Grommet
Metal ring
Foil and inner braid
Inner drain wire
Body of gland