Eden provides the Highest Safety Level and Reliability

Our recommendation is to use the Eden sensor because it is the safest and most reliable solution. The Eden sensor is both a non-contact switch and it has a dynamic function. It is also possible to connect up to 30 Eden sensors in series and still achieve a safety category 4.

What requirements should one have on switches/sensors?

The sensor/switch shall be reliable in both the safety and production point of view.

• A person must be able to trust that dangerous movements and functions are safely stopped by the sensors/switches.
• In the production point of view, unintentional stops should be avoided.

How safe is a Switch/Sensor?

In order to trust the safety function, it is essential to be aware that a safety sensor/switch must be mounted and used according to the specifications. The certification authorities only test the product according to the appropriate standards and to the specifications from the manufacturer.

Mechanical Switches

For mechanical switches (e.g. key operated), a door or hatch has to be constructed to small tolerances in order for the switch, the key or the mounting brackets to last according to the life time specification from the supplier. The screws holding the parts have to be locked in such a way that they cannot be loosened. In order to prevent material from getting into the slot for the key, the environment has to be clean.

If a door goes outside the design tolerances from wear, the screws loosen or material comes into the slot, this may lead to the interlocked switch not giving a stop signal when the door is opened. Even two mechanical switches on a door could break to an unsafe state if the door somehow gets outside the tolerances of the switches. To prevent accidents the mechanical switch normally needs continuous checks of both the switch and the installation.

Non-Contact Sensors/Switches

For non-contact sensors the risks associated with mechanical switches do not exist. If screws, brackets or sensors get loose, it will lead to a stop signal. Therefore only one sensor with dual or dynamic function is needed in order to reach the highest safety level.

There are two types of non-contact sensors - active and passive. The active sensor, Eden, is constantly communicating with a dynamic signal between the two parts and any failure will directly lead to a stop signal. The passive type, a magnet switch, has two reed con- tacts which are activated by a coded magnet. Both the passive and the active sensors are checked every time a door is opened. From a safety point of view, the active sensor, Eden, is preferred because it is checked constantly whereas the passive sensor is only checked when a door opens.

From the reliability point of view, a long detection distance with large tolerances and a well-defined on and off position is needed. The active sensor, Eden, fulfills these demands. A magnet switch has smaller tolerances and an intermediate position where only one contact opens. A bad installation or vibrations can lead to an unintentional stop if one contact opens and closes again. The supervision of a two-channel system is based on both contacts having to be operated in order to permit a new start. In a dynamic safety circuit, there is only one pulsed signal and therefore no intermediate position.