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Sistema is a software tool for evaluating safety-related machine control systems according to ISO 13849. With Sistema, you map the structure of the safety-related control parts (SRP/CS: Safety-Related Parts of a Control System) to the architectures provided by the standard. From this, you can have the program calculate reliability values at various levels of detail and the Performance Level (PL) achieved with them.
Sistema is extremely useful when you are equipping a machine with commercially available safety components (COTS SRP/CS) such as safety relays, etc. and want to prove the performance level. In this case you can rely on manufacturer libraries which contain all the necessary data of the safety components. You can outsource this calculation with Sistema. For example to the company Pilz, which provides system validation as a service.
Working with commercial safety components is not Solcept's field of activity. For us it is about developing embedded SRP/CS "on the PCB" or embedding the safety functions into your design. In these cases, commercial components are out of the question for reasons of cost or space. With such "embedded SRP/CS" you cannot fall back on data from manufacturer libraries, but you must calculate yourself the reliability values (MTTFd (Mean Time To Dangerous Failure), diagnostic coverage, etc.) of your circuit using safety analyses (FMEDA).
Such safety analyses are well known (see also our "5 Tips for an Efficient FMEDA/ Quantitative FMEA"), but they are only a small part of a product development according to a functional safety standard. You spend most of your time on implementing the basic ideas of functional safety such as: standards compliance, risk mitigation through increased quality awareness, planning, evidence and (traceability), etc. (for a complete list of activities at engineer, project team and company level, see "Development for Functional Safety: the Difference to "Conventional" Development").
Nevertheless, we recommend using the Sistema tool when developing an embedded safety component. It can be considered as a guide through ISO 13849. If you map your system in Sistema, no requirements from the standard will be forgotten and you can easily check your own calculations. Its use is particularly recommended in the planning phase. Then you can run through different scenarios and their requirements (e.g. the realization of a SRP/CS as a category 2 or 3 system) in a short time. This helps you to avoid conceptual errors right from the start.
We wish you good luck with the realization of your embedded safety components!
Please contact me if you have any questions:
Samuel Leemann
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