Access monitoring using a light curtain to SIL 3 or PL e with a 3SK2 safety relay
To monitor access to an open danger zone, so-called non-contact protective equipment such as a light curtain can be used. If the light beam is interrupted, a shutdown signal is triggered.
The light curtain consists of a send unit and a receive unit. Between the two is the protective zone. If the light beam is interrupted, outputs OSSD1 and OSSD2 carry voltage and are evaluated by the safety relay. When the light beam is interrupted, the two outputs switch off and the safety relay opens the enabling circuits, switching off the power contactors in a safety-related manner. If the light beam is uninterrupted and the feedback circuit is closed, you can switch on again. This can happen automatically or using a Start button, depending on the application.