In-depth articles tuttomisure

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Last edit: 25/08/2025

Here are the various articles we have produced in collaboration with the magazine Tutto Misure.

A total of twelve articles have been produced so far, covering various topics related to functional safety:

-Failure rates and MTTF

– The safe failure fraction and architectural constraints

– Considerations on the safe failure fraction (SFF) in high and low demand modes

– Calculating the reliability of a safety system in Low Demand (Part 1)

– Calculating the reliability of a safety system in Low Demand (Part 2)

– The mean hazardous failure rate per hour (PFH), i.e., the reliability of a safety system in High Demand

– Functional safety in High Demand: the categories of ISO 13849-1

– Functional safety in High Demand – Categories B, 1 and 2 of ISO 13849-1

– Comparison between RBD and Markov models for the analysis of Instrumental Safety Systems

– Functional safety in High Demand: The Markov Model of Category 2 according to ISO 13849-1

– Functional safety in high demand: Categories 3 and 4 according to ISO 13849-1

– Functional safety in high demand: Introduction to IEC 62061

The insights provided in the articles listed here will not be the only ones, as we collaborate with the magazine tuttomisure several times throughout the year, so get ready for future insights.

P1: Reliability data for components used in safety systems

THE QUESTION:  What are the main reliability data for components used in Security Systems? When it comes to components used…

P2: The Safe Failure Fraction and the Architectural Constraints

A Safe failure is the failure of an element, inside a component that plays a part in implementing a safety function, that results in a spurious operation of the safety function. That means, it places the machine into a safe state (it generates and em…

P3: Considerations on the Safe Failure Fraction in High and Low Demand

In a previous article we presented an important parameter, used in both high and Low Demand Mode Safety Systems: the Safe Failure Fraction.

P4.1: Functional Safety – PFD calculation First Part

A continuous probability distribution is indicated with f(x) and is usually called Probability Density Function (PDF). It is expressed by an equation and it can be represented as in the Figure 1.5 {1.4.2.1}. The bell curve is just an example of a pos…

P5: Functional Safety – PFD Calculation Second part

In the first part of the article we introduced the concepts of Unreliability function F(t) and of Reliability Function R(t). The former is the base for the parameter PFD(t) and the one used to indicate the reliability of a Safety Instrumented Functio…

P6: The average probability of dangerous failure per hour (PFH)

In the previous articles we explored the Parameter PFDavg: Average Probability of Failure on Demand. It is used to indicate the reliability of a Safety Instrumented System operating in Low demand. We will now explore the domain of Safety-related Cont…

P7: Functional Safety in High demand – ISO 13849-1 categories

ISO 13849-1 is intended to be used in the design and evaluation of safety-related parts of the control system (SRP/CS) and only the part of the control system that is safety-related falls under the scope of the standard. It applies to SRP/CS for high…

P8: Functional Safety in High Demand: Category B, 1 and 2 of ISO 13849-1

P9: a comparison between RBD and Markov models for the analysis of Safety Instrumented Systems

Within this article, the main international standards involved in Functional Safety and how they apply the Reliability Engineering Theory are investigated.

PT 10: Functional safety in high demand:The Markov model of Category 2 according to ISO 13849-1

This article is part of a series of articles written on Functional Safety of Machinery. Last year we presented the Category B, 1 and 2. Category 2 is the most difficult to understand since it is in theory a single channel architecture but that allows…

PT 11: Functional safety in high demand: Categories 3 and 4 according to ISO 13849-1

This article is part of a series of articles written on Functional Safety of Machinery. We recently introduced one of the two standards used to design Safety Control Systems in High Demand: ISO 13849-1. We remind that ISO 13849-1 is based upon a comp…

PT 12.1: Functional Safety in High Demand: Introduction to IEC 62061

This article is part of a series of articles written on Functional Safety of Machinery. We recently introduced one of the two standards used to design Safety Control Systems in High Demand: ISO 13849-1. We will now present indicated in the IEC 62061….