• Read head and evaluation electronics integrated in one housing
• Semiconductor output
• Safety outputs for directly switching up to 4 A
• Connection of the safety circuit using M23 plug connector

Reading and evaluating directly on site

The compact safety switches in the system family CES-A… combine read head and evaluation unit in one housing. The safety switches have two safety outputs and one monitoring output. All outputs are semiconductor outputs.

Non-contact safety switch CES-AH

Functional description

The Coded Electronic Safety switch CES consists of two components:

• Coded actuator
• Evaluation unit / read head

In the case of the devices described in this section the read head and the evaluation electronics are integrated in one housing.

Thanks to the high degree of protection IP67, this switch can be used directly on the safety guard in a very harsh environment. Semiconductor technology allows for a compact design of the evaluation unit and wear-free switching with a theoretically unlimited number of operating cycles.

Devices in the system family CES-AH-... have special safety outputs that are suitable for the direct switching of large loads. In appropriate applications it is therefore not necessary to connect power relays or contactors in between.

The information on the coded actuator is read by the evaluation unit and processed at the same point. The transfer of static signals (information on whether door open or closed) to the higher level switchgear permits the use of connecting cables up to 50 m long with the system.

Serial wiring, i.e. the cascading of several evaluation units, is possible. This feature makes it possible for you to implement decentralized wiring concepts with the safety switch CES.

Specifically, the major advantage of the system is that the positioning of the evaluation unit directly at the safety guard saves space in the control cabinet.

The system operator can read the current state of the safety switch on the two LED indicators (one with double function). A possible fault in the evaluation unit is indicated by a red LED. If servicing is required, the safety switch connected with an M23 plug connector can be replaced in seconds. EUCHNER supplies a corresponding mating connector.

The safety switches have a relatively large operating distance of up to 27 mm depending on the actuator. Compared with mechanical safety switches, the assembly of the unit is much easier and the need for precision in the door rails is also reduced considerably. Therefore the assembly and maintenance costs are much lower.

The safety switch with integrated evaluation unit and read head is fastened to the fixed part of the safety guard. The actuator attached to the movable part of the safety guard is moved towards the read head fitted in the safety switch by closing the door. When the switch-on distance is reached, power is supplied to the actuator by the inductive read head and data can be transferred.

The bit pattern read is compared with the code saved in the evaluation unit, if the data match the safety outputs are enabled (semiconductor outputs). A feedback loop can also be integrated here.

For the safety outputs to switch on, there must be a voltage of UB on the START input. This voltage can be supplied either using a jumper (automatic start) or using a start button.

Due to the combination of dynamic polling of the actuator and the redundant, diverse design of the safety electronics with the two feedback safety outputs, the evaluation unit will enter the safe state with every detectable fault.

The safety outputs shut down the safety circuit if the safety guard is opened. The state of the safety outputs is monitored internally by two microprocessors.

To check the safe switching function, the safety outputs LA and LB are shut down for approx. 6 ms at regular intervals. The loads connected must tolerate these pulses. Using these pulses a dangerous short circuit from 24 V to the outputs LA and LB is also detected. In the event of a fault, the safety outputs are switched off and the DIA LED illuminates red. Two LED indicators (with varying sequence of flashes) on the device make possible quick diagnostics.

The evaluation unit has a redundant switching design with self-monitoring. This means that the safety system is still effective even if a component fails.

A dangerous short circuit between the outputs LA and LB is not detected by the safety switch. In certain circumstances, however, it is possible to exclude a failure as per EN 13849_1 section 7.3 (laying connection cables with protection).

Your advantages

• Relocation of the evaluation from the control cabinet to the system
• Space-saving in the control cabinet
• Decentralized wiring concept possible
• Connection to safe control systems
• Serial connection of up to 3 devices in succession
• Connection via M23 plug connectors
• Prevention of wiring faults
• Short circuit-proof safety outputs
• High reliability
• Large operating distance of up to 27 mm depending on actuator with additional hysteresis
• Large mechanical tolerances possible for door guide
• Flush installation in door panel is possible

Reading and evaluating directly on site

The compact safety switches in the system family CES-AH-… combine read head and evaluation unit in one housing. The switches have two safety outputs. All outputs are semiconductor outputs.

Connection example CES-AH

Within the device, the shutdown of the two outputs LA and LB is dual-channel. As such, each of the outputs represents a separate safety output.

1)Load, e.g. valve coil, DC motor, Ohmic load etc.

2)In case of inductive loads, it is imperative free-wheeling diodes are used to protect the outputs on the safety switch.

Mounting

When mounting several safety switches, observe the stipulated minimum distance to avoid mutual interference.

Indication for actuator in the limit range

If the safety door with the actuator should settle over time, the actuator can drift out of the read head operating distance. The device recognizes this situation and indicates that the actuator is in the limit range. This allows the safety door to be readjusted in time.

Connection to safe control systems or safety relays

Do not use a control system or safety relay with pulsing for monitoring short circuits or switch off the pulsing function in these devices. The switch generates its own clock signals on the output lines OA/OB. A downstream device must tolerate these test pulses, which may have a length of up to 0.4 ms.

The inputs on the downstream device must be suitable for positive-switching devices (pnp outputs), as the two outputs on the safety switch deliver a level of +24 V in the switched-on state.

OUT output

(depending on version)

The semiconductor output OUT is switched if the safety guard is closed (actuator in the operating distance). It is not allowed to be used for safety functions.

DIA output

(depending on version)

The semiconductor output DIA is switched in the fault state. It is not allowed to be used for safety functions.

Reset input

(depending on version)

The switch in a fault state can be reset via the RST input. To do this, a voltage of 24 V is applied to the RST input for at least 3 seconds. It is not necessary to disconnect the supply of power to reset a fault.