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The SI-Safety module is able to detect the following faults in the external encoder
system:
•
Short circuits between the safety-related signal lines
•
Open circuits on the safety-related signal lines
•
'Stuck at 0' or 'stuck at 1' on one or all safety-related signal lines
Additional specific diagnostics for fault detection in the external encoder system are
assigned to each type of sensor. The relevant diagnostic measures are itemised below
for the individual sensor types, together with their boundary parameters.
Safety instructions
WARNING
•
The diagnostic measures naturally tend to point towards tolerances resulting from
measuring inaccuracies. These tolerances need to be considered during the
technical safety assessment.
•
Some of the limiting values for these diagnostic measures can be configured, while
others are strictly specified. The resultant diagnosis coverage levels need to be
evaluated in an application based context, and incorporated in the overall technical
safety assessment.
4.8
Configuration of measuring routes
The most important input parameters for the monitoring functions of the module are:
•
Safe position
•
Speed
•
Acceleration
These are generated on a two channel basis from the connected sensor systems. For
PL e in accordance with EN ISO 13849-1:2006, architecture corresponding to Category
4 is required, i.e. continuous two channel recording with a high level of diagnostic cover.
For any single channel components (e.g. mechanical connection of sensor/encoder with
just one shaft/mounting), it may be possible to employ fault exclusions in accordance
with EN ISO 13849-2 as a basis. For PL d in accordance with EN ISO 13849-1:2006, it
is possible to work with a reduced level of diagnostic coverage. Taking due account of
the permitted fault exclusions defined in EN ISO 13849-1:2006, it may also be possible
to use sensor systems which only feature a simple configuration (e.g. ones with only
speed monitoring capability).
Other aspects of the configuration are described in CTSafePro help.
4.8.1
Type of sensor
Absolute encoders and incremental measuring systems can be used, in addition to
proximity switches which generate/count pulses.
SI-Safety Installation & Operating Manual
Issue Number: 1
41
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