BBH SCU Series, Installation Manual

Page: 108 / 303

10
Safety-related characteristics
HB-37500-810-11-16F-EN SCU Installation Manual - Master and Slaves - SARC Page 108 of 303
Status: 09.06.2022
10.2.2.6. Safety-related evaluation of encoder systems, resolvers or their combination
Due to the monitoring functions implemented in the SCU-series, no special demands
are initially made on the internal design of the encoder electronics in applications with
encoder systems, i.e. standard encoders can normally be used.
A safety related assessment of the overall arrangement must generally be made. Data
issued by the encoder manufacturer (FIT, MTTF) as well as the DC from the table in
chapter 10.2.2.2 General diagnostic measures for encoder interface
” must in this case
be used.
When using individual encoders at least a fault exclusion for the mechanical actuating
chain, as well as for the single-channel part of must be made under due consideration
of the applicable specification in EN ISO 13849-1. Furthermore, the information in
“ 10.2.2 Sensors for speed and/or position detection “ must also be observed.
PL d and higher acc. to EN ISO13849-1 is normally reached by a combination of two
encoders with prioritized different technology and separated mechanical linking.
The use of compact encoders with internal 2-channel structure of different technology is
also suitable for applications up to PL e acc. to EN 13849-1, however, under due
consideration of the specifically required fault exclusions and their permissibility.
Normally one should use encoders with proven safety related characteristics, the safety
level of which meets the demanded level.
SAFETY NOTE 
They use of standard encoders or a combination of standard
encoders is permitted. A safety-related evaluation is strictly required
for the overall arrangement consisting of encoders,
sensors/switching elements for triggering the safety function, the
SDU module and the shutdown channel. To determine the safety
level achieved, the manufacturer's specifications (FIT, MTTF) and the
DC must be used in accordance with the requirements in ” 10.2.2 “

If only one encoder is used, the fault exclusion "shaft breakage /
fault in the mechanical encoder connection" is required. Suitable
measures must be applied for this purpose, e.g. a positive
connection of the encoder by means of slot shim or locking pin. The
applicable information issued by the manufacturer as well as EN ISO
138549-1 with respect to requirements and permissibility of the fault
exclusion must strictly be followed.

Encoders with proven safety related characteristics must preferably
be used as individual encoders. The safety level of these encoders
must at least meet the intended safety level of the overall
arrangement. The information of the manufacturer with respect to
diagnostic measures, mechanical connection and measures for the
voltage supply must be strictly followed.

SIN/COS encoder: The internal structure of the sensor system must
be designed in such a way, that output signals for both tracks can be