User manual

Berghof Automationstechnik Analog I/O expansion module
2VF100051FE01.doc 2D0172002ZD00.DOC 15
2.6. Shielding and measurement cabling
Reliable operation of higher-precision analog components with fast conversion
times can only be achieved in an industrial environment with the help of corre-
sponding shielding measures and the correct metrological cabling. The user must,
in this regard, observe the interaction of all the analog components and their auxil-
iary power supplies throughout the entire system.
Mounting the module The module must always be mounted in shielding (metal) switch cabinets/casings.
Adequate isolation of interfering components and their cabling must be ensured
within the casing by means of appropriate constructive measures (e.g. separate
wiring, spatial separation of components).
Low-frequency
interference voltages Low-frequency interference voltages, such as the omnipresent 50 Hz network
crosstalk, are cancelled out by the module’s differential measuring system in con-
junction with high common-mode rejection.
High-frequency
interference voltages High-frequency and pulse interferences have to be kept away from the signal lines
by means of suitable shielding measures.
For this purpose, the line shields in the field (outside the casing) must be connected
on both sides. The best results are always achieved when the cable shields are laid
flat at the points where they enter the casing.
Note:
Experience shows that the environmental conditions within systems and equip-
ment can change sporadically and unexpectedly.
Even if seemingly good results can be attained in a number of cases using open
wiring, we advise strongly against it.
Failure to implement the measures referred to can result in lengthy error diagnos-
tic processes and high consequential costs.
Users that implement the recommendations set out in this manual in a consistent
manner will not encounter problems regarding current EMC directives.
CE mark When designing the module, we attached great importance to its electromagnetic
compatibility. Nonetheless, a considerable proportion of the action that must be
taken in order to ensure reliable operation are outside our sphere of influence.
For this reason, we have opted not to affix the CE mark to this automation compo-
nent. In this regard we would like to draw users’ attention to their overall responsi-
bility when incorporating the module into their applications.