Building an Interlock: Comparison of Technologies for Constructing Safety Interlocks

Interlocks are an important feature of both personnel and machine protection systems for mitigating risks inherent in operation of dangerous equipment. The purpose of an interlock is to secure specific equipment or entire systems under well defined conditions in order to prevent accidents from happening. Depending on specific requirements for the level of reliability, availability, speed, and cost of the interlock, various technologies are available. Different approaches are discussed, in particular in the context of personnel safety systems, which have been built or tested at CERN during the last few years. Technologies discussed include examples of programmable devices, PLCs and FPGAs, as well as wired logic based on relays and special logic cards.