Siemens QUADLOG, Installation And Service Instruction, Page: 51 / 66

SD39RIO-1 INSTALLATION
January 2001
2-39
2.10 Terminal Block Connections
Use the following recommendations to prepare various conductors (wire ends) for connection to terminal
blocks.
Twisted Pair Connections
Twisted pair connections made to terminal blocks (as used to splice IOBUS cables) requires special attention.
It is important to preserve the continuous cable impedance as transition is made at the terminal block from
one cable to another. Provision of continuous impedance through all splice connections minimizes signal
reflections, thus assuring collision-free communications. To preserve the inherent cable impedance, make
sure that after preparing the cable ends as shown in Figures 2-12 through 2-19. Each intended pair is re-
twisted at the same intervals all the way to the wire connectors of the terminal block.
Stranded Wire Connections
Stripped ends of stranded or solid wires must not be soldered or tinned in preparation for use with DIN rail
terminal blocks. Solder is a malleable material and can loosen, causing open connections. Also, corrosion to
the terminal block can result from the pickling agents or flux used with solder.
Torque Specifications
Use the following torque specifications when tightening connections in DIN rail terminal blocks:
•
LMI (gray) DIN rail terminal blocks: 3.5 to 5.5 in. lbs.
•
Phoenix (green) DIN rail terminal blocks: 6.5 to 8.5 in. lbs.
2.11 Protective Conductor Terminal Connection
The Remote I/O Rack has two protective conductor terminals (ground lugs) located just below the left (Figure
2-29) and right sides of its backplane. Optional ground wires can be connected from this terminal to safety
ground as shown in Figure 2-3. The symbol shown in Figure 2-29 and described in Table 1-1 is located
adjacent to the terminal. Refer to APACS+ Grounding Practices (document number SD39GND-1) for safety
ground recommendations.
Figure 2-29 Protective Conductor Terminal