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E
Electromagnetic
compatibility
Equipotential
bonding
ET 200
F
Floating
FREEZE
Function
grounding
ET 200L, ET 200L-SC and ET 200L-SC IM-SC Distributed I/O Device
EWA 4NEB 780 6009-02c
Electromagnetic compatibility is the capacity of electrical equipment to work
correctly in a specified environment without negatively affecting the func-
tioning of other equipment in the vicinity.
An electrical connection (equipotential bonding conductor) that brings the
bodies of electrical apparatus and extraneous conductive bodies to the same
or approximately the same potential to prevent interfering or hazardous volt-
ages between these bodies.
The ET 200 distributed I/O system with the PROFIBUS-DP protocol is a bus
for connecting distributed I/O devices to a CPU or an adequate DP master. A
feature of ET 200 are its short response times, since only a small volume of
data (bytes) is transmitted.
ET 200 complies with the PROFIBUS standard, EN 50170 Volume 2,
PROFIBUS.
ET 200 operates on the master/slave principle. The IM 308-C master inter-
face module or the CPU 315-2 DP can be DP masters, for example.
The distributed I/O devices ET 200B, ET 200C, ET 200M, ET 200L or
ET 200U can be DP slaves, as can other DP slaves made by Siemens or other
manufacturers.
In the case of input/output modules, the reference potentials of control and
load circuits are isolated (e.g. by means of an optocoupler, a relay contact or
a transformer). Input/output circuits can be connected to common potential.
This is a control command of the DP master to a group of DP slaves.
When a DP slave receives the FREEZE control command, it freezes the cur-
rent status of the inputs and transfers them at intervals to the DP master.
The DP slave freezes the status of the inputs again after each subsequent
FREEZE control command.
The input data is not transmitted from the DP slave to the DP master at inter-
vals again until the DP master sends the UNFREEZE control command.
Grounding with the sole purpose of ensuring that the electrical equipment
functions properly. By means of function grounding, interference voltages
that would otherwise result in inadmissible interference to the equipment are
short-circuited.
Glossary
Glossary-3
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