Posted to News on 10th Oct 2006, 14:45
Fail-safe inductive sensors work with standard safety relays
Ifm electronic is launching the GM7 family of certified fail-safe inductive sensors that are safe to use up to Category 4 (EN 954-1) or SIL 3 (EN 61508). As many customer have already found, there is no longer a need to rely on mechanical devices alone in a safety application, especially when these are pushed to their limits in repetitve operations or wet areas.
Now the new GM7 series shows that the company is listening to its customers. Designed with two OSSD's (output signal switching devices) built in, the new fail-safe series will work with conventional safety relays instead of a dedicated controller - and will, of course, still work with safety PLCs or configurable safety controllers.
The GM7 series is a rectangular (40x40mm) type that senses a mild steel target located between 10 and 15mm away. No special demands such as shielding, twisted wires or separate laying are placed on the industrial-standard M12 connection. Each sensor is simply connected to existing evaluation units, safety controllers and safe bus systems using a common unscreened four-core cable.
To operate, the fail-safe switch is connected to an external safety relay of a type suitable for devices such as safety light guards, though it could equally be connected to a safety PLC running approved software.
Functional safety is assured with the ifm electronic fail-safe inductive system: coil damage, component health, cross-monitoring, short-circuit protection – all aspects are continuously checked within the device itself. Any fault, at any time, is instantly signalled.
All fail-safe inductive switches from ifm electronic are constructed with full redundant and diverse internal circuits, certified by TÜV Rhineland, but otherwise they have all the advantages of an inductive sensor: no moving parts, IP67 protection, standard M12 connectors, etc.
Lastly, do not think that an inductive sensor that needs no special target is easy to defeat, as that would defeat the object of safety. The target may be nothing special, but its position in the right place at the right time is what counts. When the target is present, any other piece of metal between the switch and the target will cause the output to switch off. Setting the unit is not difficult either, because the LED helps in adjustment, while incorporating a delay to deter any attempts to bypass the sensor.
