Simple connections

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."