This article was updated in May 2020. Author’s note: While this article is now 12 years old, the topic of EMC and Functional Safety has only become more important. IEC TC 77’s move to change IEC/TS 61000 – 1‑2 from a Technical Specification to an International Standard is evidence of this. Considering the impact of electromagnetic phenomena on the functional safety of machinery and other technical systems is an important, and often neglected, part of machinery safety engineering. I encourage readers to better understand this aspect of design and to take steps to implement additional EMC testing to better validate the robustness of their designs. – DN
At the 2008 IEEE PSES Symposium On Product Compliance Engineering, I attended a couple of interesting workshops on EMC and Functional Safety. One was called “Workshop on EMC & Functional Safety”  presented by Keith Armstrong, Bill Radasky and Jacques Delaballe. The other was a paper presentation called “Why Conventional EMC Testing is Insufficient for Functional Safety” , presented by Keith Armstrong.
For readers who are new to the idea of functional safety, this field deals with the ability of a product or system to function in it’s intended use environment, or in any foreseeable use environments, while reliably providing the protection required by the users. Here are the relevant formal definitions:
part of the overall safety relating to the EUC and the EUC control system which depends on the correct functioning of the E/E/PE safety-related systems, other technology safety-related systems and external risk reduction facilities
equipment under control (EUC)
equipment, machinery, apparatus or plant used for manufacturing, process, transportation, medical or other activities
NOTE – The EUC control system is separate and distinct from the EUC.
Table 1: (E/E/PE) electrical / electronic / programmable electronicIEC 61508 – 4:1998 
Reliability requirements are found in two key standards, ISO 13849 , , and IEC 61508 . These two standards overlap to some degree and do not define reliability categories in the same way, which frequently leads to confusion. In addition, there is a machinery sector-specific standard based on IEC 61508, called IEC 62061, Safety of machinery – Functional safety of safety-related electrical, electronic and programmable electronic control systems . These three standards make reference to EM effects on systems but do not provide guidance on how to assess these phenomena. This is where IEC/TS 61000 – 1‑2  comes into play.
All three presenters are expert members of IEC TC 77 and are directly engaged in writing the second edition of IEC/TS 61000 – 1‑2 (more info on this at the bottom of this post). This IEC Technical Specification deals with electromagnetic (EM) effects on equipment that result in functional safety problems, like failures in guarding circuits, or failures in some of the new programmable safety systems. This is becoming an increasingly important issue as programmable controls migrate into the traditionally hardwired safety world. In fact, Mr. Armstrong pointed out that EM effects are present in many of our “tried and true” circuits, but the failures have been incorrectly attributed to other phenomena because most electrical engineers have not been used to thinking about these phenomena, especially in 24 V d.c. relay-based control circuits.
In the workshop, the presenters discussed a typical product life cycle, then went on to explore the typical environments that a product may be exposed to, including the EM and physical environments. They went on to discuss the need for an EMC-related Risk Assessment and then finished up by looking at Electromagnetic Safety Planning. The whole workshop took the entire second day of the Symposium.
A key point in the workshop is that conventional EMC testing cannot practically prove that systems are safe. This is due to the structure of the EMC tests that are normally undertaken, including the use of fixed modulation frequencies during immunity testing, failure to assess intermodulation effects and many other issues. In addition, EMC testing does not and cannot test for aging effects on performance, wear & tear and other use-related conditions. The presenters discussed a number of ways that these problems could be addressed and ways that testing could be extended in selective ways to attack predicted vulnerabilities. Conventional EMC testing does not consider the reliability requirements of the tested product (i.e. IEC 61508 – 1 SIL‑3 or SIL‑4).
On the following morning, Keith Armstrong presented his paper. In this paper, Mr. Armstrong went into considerable detail on the shortcomings of conventional EMC testing when it comes to Functional Safety. He suggested some approaches that could be used by manufacturers to address these issues in safety-critical applications.
The workshop presentations and Mr. Armstong’s paper can be purchased through IEEE Xplore for those that did not attend the Symposium.
The IET has published a book entitled Electromagnetic Compatibility for Functional Safety. Unfortunately, this book is no longer available from the IET, however, here is another source.
Keith Armstrong, Bill Radasky and Jacques Delaballe are members of IEC Technical Committee 77. Since the original publication of this article in 2008, IEC/TS 61000 – 1‑2 Ed 2.0, has been withdrawn and converted to an international standard, published as IEC 61000 – 1‑2 .
Jacques Delaballe works for Schneider Electric Industries SAS in Grenoble, France.
 2008. Workshop On EMC & Functional Safety.
 K. Armstrong, “Why Conventional EMC Testing is Insufficient for Functional Safety,” in IEEE PSES Symposium On Product Compliance Engineering, 2008.
 Functional safety of electrical/electronic/programmable electronic safety-related systems – Part 4: Definitions and abbreviations, IEC 61508 – 4. International Electrotechnical Commission (IEC), 1998.
 Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design, ISO 13849 – 1. International Organization for Standardization (ISO), 2006.
 Safety of machinery — Safety-related parts of control systems — Part 2: Validation, ISO 13849 – 2. International Organization for Standardization (ISO), 2003.
 Functional safety of electrical/electronic/programmable electronic safety-related systems, IEC 61508, seven parts. International Electrotechnical Commission (IEC), 1998/2000.
 Safety of machinery – Functional safety of safety-related electrical, electronic and programmable electronic control systems, IEC 62061. International Electrotechnical Commission (IEC), 2005.
 Electromagnetic compatibility (EMC) – Part 1 – 2: General – Methodology for the achievement of functional safety of electrical and electronic systems including equipment with regard to electromagnetic phenomena, 2nd Ed., IEC/TS 61000 – 1‑2. International Electrotechnical Commission (IEC), 2008.
 Electromagnetic compatibility (EMC) – Part 1 – 2: General – Methodology for the achievement of functional safety of electrical and electronic systems including equipment with regard to electromagnetic phenomena, 1st Ed., IEC 61000 – 1‑2. International Electrotechnical Commission (IEC), 2008.