The Latest Generation of Safety Relays

The latest generation of safety relays operates using microprocessor technology. This technology is used in the PNOZsigma product series, for example, and offers further additional benefits over conventional relays. There is less wear and tear thanks to the use of electronic evaluation procedures and the diagnostic capability, plus the safety relays also reduce the number of unit types: One device can now be used for a variety of safety functions, e.g. for emergency off/emergency stop, safety gate (contact-based switches as well as switches with semiconductor outputs), light beam devices, light curtains and two-hand control devices. As electronic safety relays have a more compact design, they take up much less space. The reduced size enables more functions to be implemented in the same effective area. Selectable operating modes and times allow for  flexible application of the devices. As a single device type can implement several different safety functions at once, savings can be made in terms of stockholdings, configuration, design and also when commissioning plant and machinery. Not only does this reduce the engineering effort in every lifecycle phase, it also simplifies any additions or adjustments that are required.


Electronic safety relays can be expanded in the simplest way possible. Whether you use additional contact blocks or function modules: Adapting to the specific requirements of the respective plant or machine is a simple, straightforward process, with contacts expanded via connectors. With just a single base unit, plus additional expansion units if required, users can fully implement all the classic functions.

An Overview of Safety Relays

Safety relays perform defined safety functions:
For example, they:

• Stop a movement in a controlled and therefore safe manner
• Monitor the position of movable guards
• Interrupt a closing movement during access

Safety relays are used to reduce risk: When an error occurs or a detection zone is violated, they initiate a safe, reliable response. Safety relays are encountered in almost every area of mechanical engineering, mainly where the number of safety functions is quite manageable. However, increasing efforts are being made to integrate diagnostic information into control concepts as well as overall concepts. That's why in future safety relays with
communications interfaces will be more prevalent in plant and machinery.

Safety relays have a clear structure and are simple to operate, which is why no special training measures are required. To use these devices successfully, all that's generally needed is some simple, basic electrical knowledge and some awareness of the current standards. The devices have become so widely used because of their compact design, high reliability and, importantly, the fact that the safety relays meet all the required standards. They have now become an integral component of any plant or machine on which safety functions have a role to play.

Since the first safety relays were developed – initially with the sole intention to monitor the emergency  off/emergency stop function – a wide range of devices have now become established, performing some very specific tasks in addition to the monitoring functions: for example, monitoring speeds or checking that voltage is disconnected on a power contactor. The devices are designed to work well with the sensors and actuators currently available on the market. Today, a safety relay is available for practically every requirement. With their
diverse functionality, safety relays can implement almost any safety function, for example, monitoring the whole safety chain from the sensor to the evaluation logic, through to activation of the actuator.