User Manual

4 Catalog E 074441 01/06 Edition 4 www.erni.com
General Information
The development of bus systems for industrial applications
began in 1983. To be more accurate, it was the use of serial
data transmission which brought about the breakthrough. In
1988, field bus systems were still new in industrial automati-
on and a great deal of effort was required to win customers.
But within a very short time, so-called field bus systems
have gained acceptance to an extent that no one could have
dreamed of.
This has only been possible because customers have simply
been made aware of a clear product advantage. From then
on, it was no longer necessary to individually wire device for
device and signal for signal; instead so-called “bus nodes”
could be installed, which communicate with one another by
means of a 2-wire cable and pass on commands to the input
and output modules. In this way, installation expense and
the possibility of faults were considerably reduced. Added
to this are features such as remote diagnostics, parameter
setting and modularity, to name but a few. Of the multitude
of field buses that came onto the market, some have almost
disappeared again. The large control system manufactu-
rers are trying to establish their systems in the marketplace
through so-called user organizations, e.g. PNO (Profibus
User Organization), CiA (CAN in Automation), SafetyBUS p
(SafetyBUS Club), and other marketing activities.
A fundamental difference is constituted by the different net-
work topologies. Hence, there are line, ring or star configura-
tions. All have their particular advantages and disadvantages.
Device hierarchies are also possible: master-slave systems or
multi-master systems.
A characteristic of the line configuration is that the bus must
be “terminated” by means of a resistor at the end of the line
in order to avoid effects such as reflections, which may inter-
fere with the communication.
Devices within the line are cabled by “looping through”. Here,
the T function, which enables the bus to operate when the
plug is removed, is of particular interest.
ERNI is currently concentrating on Profibus, CAN bus and
SafetyBus p versions where, at the same time, customer-
specific solutions e.g. for Bitbus, Interbus, etc. also exist.
In the meantime, some bus systems have been international-
ly standardized. The so-called physical layer is also defined
in these standards, which, among other things, specify the
cable, the connectors and the contact assignment. There are
still differences with regard to the protection class. Different
plug connectors are recommended depending on this. The
term “light duty” is used with IP 20 and “heavy duty” with IP
65/67.
ERNI bus interface connector,
ERbic for short
The interface plugs of the ERbic line for various bus systems
offer different features and advantages. They are based on
D-Sub interface technology. All ERbics have compact exter-
nal dimensions. There are versions with horizontal and vertical
cable outlets.
Both pure node versions and pure termination versions are
available as well as nodes with a connectable termination
resistor. The node (without termination resistors) is used
within the length of a line and the termination (with terminati-
on resistors) at the end of the line. The node with a connec-
table termination resistor can be used anywhere. The latter is
simply configured as a termination by changing the position
of the switch.
The housings of the pure terminations are a different color
than the nodes. The end of the line is therefore immediately
recognizable.
The bus systems are also different colors. The user can the-
refore easily find their way around within a system.
A T function is provided in all ERbics. A device can therefore
be changed while the bus is running. The types with a con-
nectable termination resistor are primarily suitable for custo-
mers with reduced storage or when setting up, extending or
converting large systems.
Certain types are reversed with regard to the face of the con-
nector, allowing the direction of the cable outlet to be deter-
mined. This is achieved by a special pin arrangement in the
D-Sub connector.
However, the standard direction of the cable outlet is mat-
ched to the devices of the market leaders and should there-
fore be used for new designs.
A further outstanding feature is the termination technology.
Depending upon the type, ERbics are available with screw
terminals, cage-clamp terminals or IDC terminals.
Terminations using the Siemens FastConnect principle, for
example, are therefore possible.
The development of field buses in the direction of safety-
related applications is also satisfied by corresponding further
advancement of the ERbic line. There is a Profibus Ex i versi-
on, which was developed together with ABB, or a SafetyBus
p version for the Pilz company.
As an alternative to the plastic housing, the newly developed
ERbic MAX has recently been introduced to the market. This
has a metal housing and an axial cable outlet. It is particularly
suitable for harsh environments and offers space advantages
at the field device when several interfaces are present.
The metal housing guarantees optimum EMC.