The safe-state, with the outputs high, is given when the target is not present, i.e. outside the 10mm enable zone, in the area known as the safe switch-off zone. If a metal object is in the enable zone, the outputs are switched on.
The operating principle can be illustrated using the example of gantry crane: a fail-safe sensor monitors the position of the crane on the gantry. With a normally open version the sensor would need to be damped along the whole travel in order to maintain the safe function; the sensor being undamped only at the stop positions. This new version allows mounting of only one target, at the beginning and at the the end of the crane track, which saves material and mounting cost.
The GG851S sensor has two OSSD outputs for connection to a safety relay or PLC, dignostics and status displayed via local LEDs. No special target is required and the GG851S is fully flush mountable. The fail-safe sensor is certified to ISO 13849-1 PL d, IEC 61508 SIL 2 and IEC 62061 SIL cl2.
Connection is via a standard M12 connector, which is available from the EVC range also manufactured to exacting specifications by ifm electronic. The sensor has a wider operating voltage than earlier versions, allowing operation down to 12Vdc.