ASi-5 Safety

ASi-5 Safety has been an integral part of ASi-5 from the very beginning: both use the same communication technology. In the case of ASi-5 Safety modules, only the normatively required protection of the data is added - with an additional checksum.This makes the transmission of these signals functionally safe up to SIL 3/PLe. This is essential whenever standards require such functional safety to protect people and the environment.

Just like ASi-3 Safety at Work, ASi-5 Safety was once again tested and certified externally according to applicable functional safety standards. Similarly, the process used for ASi-5 Safety achieves a performance level up to PLe according to ISO 13849-1, or a safety integrity level up to SIL3 according to IEC 61508/62061.

Of course, even standard sensors can be connected to ASi-5 Safety modules. With many modules, it is even possible to reconfigure connections so that the signal of the standard sensor is only transmitted via the standard protocol. This especially conserves communication resources such as addresses and bandwidth for ASi-3 Safety modules.

An additional advantage of ASi-5 Safety is that many safe and standard signals can be connected and transmitted over a single address. This saves resources and above all costs.

The topic of cyber security is more relevant than ever. In the industrial sector, the reliability of processes and production in particular is becoming increasingly important.

Like the standard ASi-5 communication, ASi-5 Safety is almost tap-proof due to the nature of the system. The reason:  the data transfer via OFDM with dynamic frequency assignment,makes it very complex to capture the exchanged messages. This requires the entire context of the connection set-up between ASi master and ASi node. Besides, the clock frequencies must be precisely synchronized just like between the ASi master and ASi node according to the ASi-5 protocol.

Cyber security is also enhanced by the fact that the gateway creates a logical break between TCP/IP, ASi-5, and ASi-5 Safety. This means that high safety requirements only need to be placed on the ASi-5 Master, which establishes the connection to TCP/IP. ASi-5 modules, on the other hand, are much less problematic in terms of safety, since they cannot communicate over TCP/IP networks. Those responsible for network security can thus focus on significantly fewer devices and check them more carefully.

Like ASi, ASi-5 Safety is characterized by maximum stability and availability. Defective masters can therefore be replaced easily and without complications: Thanks to the backup in the ASi master, the replacement device is automatically addressed and parameterized just like the original device .

ASi-5 Safety is very flexible: depending on the profile and application scenario, 1 to 64 safe process data along with additional standard  – each bidirectional – can be exchanged with one module. In the process, cycle times of up to 1.27 ms can be achieved for up to 16 safe inputs and 16 safe outputs each. Available diagnostics and acyclic services have no influence on the cycle times.

As an integral part of ASi-5, ASi-5 Safety can transmit safe and standard data simultaneously. Up to 32 bytes are available cyclically for this purpose. The safe data always has a 1-byte checksum, which enables safe communication up to level SIL3/PLe. As with pure ASi-5 standard modules, there is also a diagnostic and an acyclic channel. This also allows ASi-5 Safety modules to transmit detailed diagnostic messages in case of an event. An additional high-performance method is also available to read out additional information if required – e.g., for predictive maintenance or similar applications.

ASi-5 Safety uses the same mechanisms as all other ASi-5 modules. This means that it provides cyclic data along with an event-based diagnostic channel and an acyclic channel for reading out numerous indices. These indices cover a wide range of information: manufacturer, model name, the ASi ID for unique identification, module temperature, measured currents or an hour meter, to name a few." OPC UA enables this information to be transmitted to IT for evaluation.

This can save considerable costs in applications with multiple signals. ASi-3 Safety can also be used for modules that have many signals. In this case, however, each safe signal occupies a separate address. Just as with ASi-5, ASi-5 Safety can process much more data per master and thus greatly reduce connection costs – thanks to the significantly higher data bandwidth per address. For example, with the ASi-5 Safety module BWU4210, a total of 2x2-channel safe inputs and an additional 12 I/Os are available under just one ASi-5 address. In contrast, the same amount of data occupies 2 single and 3 A/B addresses with ASi-3.

However, ASi-5 may not always be the most advantageous one. Even with ASi-3 Safety, only one address is occupied for a single E-stop with a 2-channel safe input – and at lower cost. Both technologies will therefore be used in parallel in the future.

ASi-5 and ASi-3 operate independently and in parallel on the same two-conductor cable with the same electromechanics. Only one gateway with a combined ASi-5/ASi-3 master is required when using both protocols in one installation. The same applies to ASi-5 Safety and ASi-3 Safety – all that is needed is a gateway with a combined master and a combined ASi-5/ASi-3 safety monitor. In the simplest case, it is therefore possible to just replace the gateway in an existing system with ASi-3 Safety. The system can then continue to operate without changes, and ASi-5 Safety modules can be easily added if necessary.