With its new TR4 Direct safety sensors
for doors and gates, Sick says it has
solved the problem of cost-effective
series connection of up to 30
switches, achieving PLe, Cat 4
integrity and full diagnostic coverage
of an installation.

Sick says the TR4 Direct noncontact
sensors overcome the
limitations on series connection
imposed by the BS EN13849-1 and
ISO/DIS14119.
Seb Strutt, safety specialist, says:
“In high risk applications where PLe
or even PLd interlocking is required,
fault exclusions are not advised in
relation to mechanical actuators.

Series connection of switches must
consider the potential for faults to
remain undetected and should reflect
this fact in the declared diagnostic
coverage of the functional safety
system. Sick’s TR4 Direct safety
sensors enable simple, cost-effective
series connection to continue. They
ensure reliable monitoring of multiple
access installations with full diagnostic
coverage of individual faults.”