Technical information

44
230V FX Series Positioning Drive Reference Manual
In multi-drop configurations the ground reference (earth ground) for each communicating
device must be at the same potential. The further apart the communicating devices the more
difficult this is to achieve. Therefore, it is a good idea to keep the multi-drop loop as short as
possible. This condition is not as critical if all of the communicating devices are optically
isolated (the serial bus ports in all FX drives are optically isolated). However, if more than
one device in the loop is not optically isolated proper grounding becomes critical.
Performance Code C
The DPC-XXX cable is the only performance code “C” cable. This cable is used for the
parallel interface connections to the thumbwheel and digital display products. The maximum
length is limited to 50 feet because of the noise susceptibility of the digital signals.
Performance Code D
Performance code “D” cables are used for PCM module applications with encoder signals.
The specification of 100 feet /140 feet maximum is a total length from the encoder to the last
drive in the “chain”. For example, if your system is configured with an SCS encoder and three
FX drives in a multi- drop configuration, the total length of the MSC cable plus the two SSC
cables should not exceed 100 feet.
Figure 31: Encoder Cable Connections on a Multi-Axis Application
The maximum length of 140 feet has been successfully tested by EMERSON Motion Control
in an electrically quiet environment. In an electrically noisy factory environment the shorter
the cables connecting the devices the better. This will help reduce noise problems.
It is very important that the EMERSON Motion Control cables listed in “Motor Wiring
Requirements” on page 49 are not altered in the field. It is also important to follow any
recommendations given in this or any other EMERSON Motion Control product manuals on
connecting or terminating these cables.
As a general rule, the minimum cable bend radius is ten times the cable outer diameter.
SSC-XXX
CABLE
MSC-XXX
CABLE
SCS-X
ENCODER
FX AMPLIFIERS WITH
PCM APPLICATION
MODULES