Danaher Motion
05/2008
Detailed Wiring Information
S200-CNS Product Manual
47
10.2 D
EFINITIONS
D
ISCUSSION
Bred from the older days of PLCs and the newer days of digital logic some words have become
standard in some industries. Some terms are described here to make this document easier to
understand:
Common Rail: Common rail is simply a term meaning that more than one input (or output) has one
terminal of its device tied to the other inputs (or outputs). An example of a common rail is shown
below:
Figure 8.1 Common Rail Illustration
In Figure 8.1 each input is represented by the LED. Each input has a common connection (Anode)
to the positive side of the I/O power source. This is what is referred to as a common rail. It is also
allowable to modify this circuit where each anode goes to the switch and each resistor is tied to the
negative side of the I/O supply.
Sourcing Input: A sourcing input is an input that must be taken to ground to operate. (It SOURCES
current). The above figure shows discrete inputs arranged for sourcing. These are used with sinking
output device such as Open Collector drivers. Some manufacturers of driving devices refer to
sinking outputs as ‘NPN’ devices after then name of the driving device transistor type.
Sinking Input: A sinking input has the opposite arrangement of souring inputs where a current-to-
ground must be supplied to the input. (Sinking current to ground). These are used with sourcing
output devices. Some manufacturers of driving devices refer to sinking outputs as ‘PNP’ devices
after then name of the driving device transistor type.
10.3 PE
E
ARTH
G
ROUND
C
ONNECTIONS
It has been noted throughout this manual that a connection to earth ground is required. Multiple
connections may be required. The connection to earth ground can affect safety and electrical noise
immunity and emissions. The purpose of this text is to alert the user to the requirement of the earth
ground connection. When connecting earth grounds it is often required to have a connection that
can not come undone so ring lugs to the frame is highly recommended. Each earth ground wire
should go directly back to the central earth ground block in the cabinet; do not daisy-chain the
connections. Large gage wires consisting of many fine strands of wire are superior to other types for
conducting high frequency noise and the use of high strand count wire is recommended.
