science

Profisafe

Profisafe is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Profisafe rather than just read about it. In short: Profisafe (usually styled as PROFIsafe, as a portmanteau for Profinet or Profibus safety) is a standard for a communication protocol for the transmission of safety-relevant data in automation applications with functional safety. This standard was developed jointly by several automation device manufacturers in order to be able to meet the requirements of the legislator and the IFA for safe systems.

Key takeaways

Profisafe belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Profisafe to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Profisafe from memory before moving on to harder problems.

Reference excerpt

Profisafe (usually styled as PROFIsafe, as a portmanteau for Profinet or Profibus safety) is a standard for a communication protocol for the transmission of safety-relevant data in automation applications with functional safety. This standard was developed jointly by several automation device manufacturers in order to be able to meet the requirements of the legislator and the IFA for safe systems. The required safe function of the protocol has been tested and confirmed by TÜV Süd. The PROFIBUS Nutzerorganisation e.V. in Karlsruhe supervises the standardization for the partner companies and organizes the promotion of this common interface.

System structure Profisafe defines how safety-related devices (emergency stop buttons, light curtains, overfill prevention devices, ...) communicate safely with safety controllers via Profinet, Profibus or a backplane in such a way that they can be used in safety-related automation tasks up to SIL3 (Safety Integrity Level). Due to the specification of Profisafe, products of different manufacturers can be combined to a safe system.

Market relevance The first version of Profisafe was released as early as 1998. A second version in 2005 also enabled use via the Ethernet-based Profinet. According to the PROFIBUS Nutzerorganisation e.V., by 2023 a total of almost 21,7 million devices with Profisafe will be placed on the market by the various manufacturers, and a further 2.8 million devices will be added each year. In the database of the PROFIBUS Nutzerorganisation e.V., 106 different products from 31 different manufacturers are entered in October 2022.

Operating principle With Profisafe, secure communication is implemented via a profile, i.e., via a special format of the user data and an additional protocol. Safety-relevant data are transported with Profisafe as F-messages between an F-Host (safety controller) and its F-Device (safety device) as payload in a telegram of an industrial network. In the case of a modular F-Device with several F-modules, the payload consists of several F-messages. In this case Profisafe has no further requirements for the transmission channel, this is considered as a black channel. Therefore different transport protocols like Profibus or Profinet can be used. Different transmission channels such as copper cable, fiber optic cable (FOC), backplane bus or wireless systems such as WLAN can be used. Neither the transmission rates nor the respective error detection of the transport protocol play a role for safety. The following figure shows the format of the payload of a "Safety Protocol Data Unit (SPDU)":

The cyclic redundancy check (CRC signature) is calculated over all local security parameters, the transmitted data and the locally stored monitoring number of the SPDU. This ensures that all information from the sender and the receiver is consistent without having to always transmit all parameters. The monitoring number enables the recipient to check whether he has received all the messages in the correct sequence. With the acknowledgement, the monitoring number is returned to the sender for checking within a defined maximum delay time (timeout). Since some bus components, such as switches, have a buffer memory, a 32-bit monitoring number was selected for Profisafe. The 1:1 communication relationship between F-Host and F-Device simplifies the detection of misdirected F-messages. For this purpose, the sender and receiver require a unique identifier (code name) throughout the network, which is used to verify the authenticity of F-messages. In Profisafe, the code name is also called "F-Address". The following table shows which errors can be detected by which measure:

Specification The international standard IEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems. IEC 62061 Safety of machinery - Functional safety of safety-related electrical, electronic and programmable electronic control systems and ISO 13849 Safety of machinery — Safety-related parts of control systems are also the basis for Profisafe. The international standard IEC 61784-3 defines different protocols for safe systems with comparable properties. Profisafe is part 3 of this collection of standards and is thus defined as IEC 61784-3-3:2021 CPF 3.

See also Functional safety IEC 61784-3 Industrialcommunication networks – Profiles – Functional safety fieldbuses IEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems IEC 62061 Safety of machinery - Functional safety of safety-related electrical, electronic and programmable electronic control systems ISO 13849 Safety of machinery - Safety-related parts of control systems

References

Worked examples

Example 1 — a first encounter with Profisafe

Start with the simplest possible case. Write down what Profisafe claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Profisafe before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Profisafe ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Profisafe

In research: Profisafe appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Profisafe in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Profisafe is common in secondary-school and first-year university syllabi. It links to neighbouring topics Industrial automation, so understanding it makes those chapters shorter.
In everyday life: Look for Profisafe outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Profisafe in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Profisafe means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Profisafe out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Profisafe in simple terms?

Why does Profisafe matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Profisafe?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Profisafe.