'Intelligent' expansion modules maintain PLd for series sensors

To ensure the safety of machines and systems, moveable guards such as doors and flaps are monitored with safety switches. An interface or an input expansion unit can be used to avoid having to wire them individually in the switch cabinet. This means that only one cable is connected to the safety relay. With most input expansion units, not all errors can be detected when this cascading process is utilised, which makes it difficult to achieve performance level 'd' in accordance with safety standard EN ISO 13849-1.

elobau has therefore equipped its existing interfaces with 'intelligence' in the form of control outputs. This means each error can be reliably detected with an additional monitoring method, even when switches are connected in series. Thanks to the electronic monitoring of individual channels, even without the use of a standard PLC, performance level 'd' can be maintained. The costs of the new interface and the additional measures are negligible compared with wiring the sensors individually.

The 'intelligent' interface enables up to four safety switches to be connected to one sensor input on the safety relay. The 470 series relay shown in the wiring diagram has two sensor inputs, allowing for the connection of two input expansion units, thereby enabling up to eight safety switches to be connected to one safety relay.

Follow the link for more information about the new 'intelligent' input expansion modules from elobau.