In Compliance: The Compliance Information Resource for Electrical Engineers logo
Continuing Your
Professional Education in 2022
Continuing Your
Professional Education in
Failures Caused by
Ground Potential Rise at Interconnected Houses

Navigating the
“Safety Hierarchy”

A Recipe for Success:
How to Grow from EMC Novice to EMC Expert

two pencils and their shadow that shows a ladder
Failures Caused by
Ground Potential Rise at Interconnected Houses

Navigating the
“Safety Hierarchy”

A Recipe for Success:
How to Grow from EMC Novice to EMC Expert

January 2022
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January 2022
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January 2022
Volume 14 l Number 1
By the In Compliance Staff
Traditionally, the start of a new year is a time when we reflect on the progress we’ve made during the year passed and set our goals for the new year. We’ve queried training resources in our industry to provide you with an overview of free or affordable solutions to meet your training goals in 2022.
By Albert R. Martin
Much has been written about failures due to ground potential rise (GPR), generally in connection with single houses with multiple grounds. But in cases where multiple houses are interconnected via a single piece of equipment, equipment failures could be caused by insulation issues due to GPR attributable to lightning.
By Kenneth Ross
The safety hierarchy is a flexible concept that can be helpful in deciding on a final product design. But it can also be a trap for the unwary design engineer. This article will discuss the safety hierarchy concept, how do you comply with its requirements, and what are the problems associated with it?
By Daryl Gerke, PE
For engineers new to the field of EMC, the road can look very steep indeed. But, with a plan (and some work!), you can grow from EMC novice to EMC expert.
man sitting ask desk
gavel on top of pile of files
sticky note with Never Stop Learning written on it
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EMC Concepts Explained
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On Your Mark
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Hot Topics in ESD
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compliance news
FCC Expands Space Access for IoT Support
The U.S. Federal Communications Commission (FCC) has granted a French satellite company permission to provide satellite-based connectivity services for Internet of Things (IoT) devices.

According to a press release issued by the FCC, the company, Kinésis, proposed the deployment of a constellation of 25 small, low-Earth orbit satellites and was seeking permission…

EU Commission Updates List of Harmonized Standards for Toys
The Commission of the European Union (EU) has published an updated list of standards that can be used to demonstrate conformity with the essential requirements of its directive relating to the safety of toys (2009/48/EC).

According to the Directive, toys are defined as “products designed or intended…for use in play by children…

DILBERT Comic strip
DILBERT © 2022 Scott Adams. Used By permission of ANDREWS MCMEEL SYNDICATION. All rights reserved.
Feature Article
Continuing Your Professional Education in 2022
Compiled by the In Compliance Magazine Staff
man at table with hand to chin

s the world gradually (and cautiously!) reopens after the past two years, we optimistically predict that 2022 will be like no other year in recent memory. Companies and industry professionals will go bold in exploring new ideas and pursuing previously unseen opportunities to bring new and innovative technologies to market. And, with supply chain workarounds taking effect, commercial and consumer markets will bounce back in ways that would have been the stuff of fantasies pre-pandemic.

In this promising time, your ongoing personal efforts to refresh or expand your professional and technical knowledge are more important than ever. So, as 2022 begins, we’ve once again queried training resources throughout our industry to provide you with an overview of free or affordable solutions to meet your training goals in the new year. In this article, you’ll find sources of compliance-related seminars, workshops, and other types of training, offered live, including both virtual and in-person options, as well as pre-recorded webinars and on-demand training offerings.

Feature Article
Failures Caused by Ground Potential Rise (GPR) at Interconnected Houses
How Interconnects are a Path for Potential GPR-Caused Failures
By Albert R. Martin
Editor’s Note—We are grateful to the family of Al Martin for giving us permission to publish this article posthumously and to honor Al and all his contributions to our industry during his long and industrious career. We would also like to thank Mick Maytum and Joe Randolph for their assistance in preparing the initial draft for publication. Thanks to you all!


uch has been written about failures due to ground potential rise (GPR). So, is there anything more to say? Well yes. What has been written has generally been about single houses with multiple grounds. But often there is not just a single house, but multiple houses all potentially interconnected via a single piece of equipment. For example, in homes connected to a distribution point unit (DPU) (see Figure 1) the DPU is often a fiber-to-the distribution point (FTTdp) unit, or a digital subscriber line access multiplexer (DSLAM). So, what happens in this case?

Well, what could happen is insulation failure. This kind of failure was discussed in a 2011 study by the Japanese telecommunications company Nippon Telegraph and Telephone (NTT). That company had a problem. About 0.05% of their optical network terminal/home gateway ONT/HGW boxes stopped working due to insulation failure. Now 0.05% doesn’t sound like much, but with 15 million installed devices, that amounted to 7500 units per year. Their research showed that the 0.05% failure rate corresponded to a 7.7 kV surge. Assuming that 0.05% (or less) is an acceptable failure rate, could GPR cause the corresponding 7.7 kV insulation failure?

Feature Article
Navigating the “Safety Hierarchy”
Designing Safe Products and Minimizing Risk
By Kenneth Ross
Judge's gavel

ne of the key issues that must be decided by any manufacturer when designing new products or improving current products is how safe is safe enough and whether there is a reasonable alternative design that can be adopted at a reasonable cost. Unfortunately, the law and standards don’t answer the question. And a risk assessment, although helpful in quantifying risk and identifying alternative designs that might improve safety, also does not answer the question.

So how does a manufacturer make a final design decision? The manufacturer should first consider all applicable safety standards that affect the product’s design and whether competitors comply with or exceed those standards. The manufacturer should then engage in some type of risk assessment that identifies and quantifies risks in the contemplated design, as well as the various ways in which those risks could be reduced, such as by using a different design, guarding, warnings, instructions, training, etc.

At that point, the manufacturer must decide what design features to apply to their product, including any guarding, and when can they rely on these techniques to sufficiently reduce overall risk. This decision is most critical to the safety of the product in actual use, as well as a possible defense against potential claims that the product is unsafe.

Feature Article
A Recipe for Success: How to Grow from EMC Novice to EMC Expert
Some tips from an industry veteran to help you navigate the world of EMC
By Daryl Gerke, PE
Never Stop Learning post-it note

Editor’s Note—Originally published in our March 2014 issue, this article remains one of the most popular articles among readers of In Compliance Magazine. The most recent version of this article was published in our January 2020 issue.


t’s been said that nobody grows up wanting to be an EMC engineer. Rather, it usually just happens. Maybe you had incriminating information on your resume, such as being a radio ham. “You’ve created interference, so you must know how to stop it, right?” Maybe you showed a knack for EMC troubleshooting, and suddenly you’re now the company expert – whether you want to be or not. Or maybe you just zigged when you should have zagged.

In any event, you’re now in the EMC trenches. In this article, we’ll discuss what to do next. It won’t happen overnight, but with a plan (and some work), you can move from EMC-novice to EMC-expert.

EMC concepts explained
Evaluation of EMC Emissions and Ground Techniques on 1- and 2-layer PCBs with Power Converters
Part 8: AC/DC Converter – Baseline EMC Emissions Evaluation
By Bogdan Adamczyk, Scott Mee, and Nick Koeller

his is the eighth article in a series of articles devoted to the design, test, and EMC emissions evaluation of 1- and 2-layer PCBs that contain AC/DC and/or DC/DC converters and employ different ground techniques [1-7].

In this article, we evaluate the performance of the baseline AC/DC converter. The baseline AC/DC converter has only the components needed for functionality and does not have any specific EMC components populated. [7] This configuration will give us a view into what the conducted and radiated emissions issues will be prior to adding components and the cost to specifically address EMC issues. We present the test results from the baseline radiated and conducted emissions tests performed according to the CFR Title 47, Part 15, Subpart B, Class B.

hot topics in ESD
What Are External Latch-up and Internal Latch-up?
By Wei Liang, Robert Gauthier Jr., and Souvick Mitra for EOS/ESD Association, Inc.
What is a Latch-up Event?
As one of the major reliability concerns for the semiconductor industry, a latch-up event in bulk complementary metal-oxide-semiconductor (CMOS) technology originates from the base-collector coupled parasitic negative, positive, negative (NPN) (also known as sinking) and positive, negative, positive (PNP) (also known as sourcing) bipolar transistors. The placement of the N-type and P-type devices in close proximity will result in the parasitic silicon-controlled rectifier (SCR) structure. Figure 1 and Figure 2 show the parasitic SCR structure in a CMOS inverter and the simplified parasitic SCR structure. When a latch-up event is triggered, a low resistance path forms between supply and ground, and a significant amount of current can flow through this parasitic path. This could, in most cases, lead to substantial chip damage when it is a sustained latch-up event that is being triggered. Holding voltage (Vh) is the minimum voltage required to keep the SCR structure at the on-state. A sustained latch-up event happens when the supply voltage (VDD) is higher than the Vh of the parasitic SCR structure because the VDD is high enough to keep the SCR turned on and won’t unlatch once it is triggered.
on your mark
Product Safety and Liability:
A Historical Overview
By Erin Earley
A Look at How the Past Has Shaped Today’s Approaches

n our last On Your Mark column, we explored key components of a comprehensive product safety strategy – from risk assessment to safety labels and manuals – and ways those elements work together to improve safety and reduce risk. How did we get here – why are certain perceptions and directives in place – and how do they differ across the globe? History is very telling in influencing the trajectories of product safety and liability. To get the details, we turned to insight from Doug Nix, Managing Director of Compliance inSight Consulting and lead author of the Machinery Safety 101 blog, with over 30 years of industrial safety experience specializing in machinery safety and risk assessment methods. Read our interview with Nix for context on how the past has shaped the ideology and approaches that we employ today.

Give us a brief historical overview of product safety and liability.

In the early part of the Industrial Revolution, there really was no product safety. The basic workplace safety premise was that workers had the right to negotiate their contracts of employment with their employer to get a fair deal. That ended up giving employers all the power and workers none. From the workplace safety perspective, generally speaking, the attitude was that if a worker was injured using a piece of equipment, they were lazy or incompetent; the equipment wasn’t blamed. In historical photos of machines in the workplace at the end of the 19th century and the beginning of the 20th century, you’ll see open flywheels and other issues recognized today as obviously dangerous. But, that wasn’t the prevailing thinking at that time.
Interference increasing in the aircraft bands

Very little has happened to Section 21 recently other than a reduction of the limits in the receiver band for certain test categories and the banning of circularly polarised antennas, with both horizontal and vertical testing being required above 25MHz. However, more significant changes…

EMI suspected of causing electrical meltdown

Question: I have a Rover 827 Si, bought new in Spain in 186. When I travelled to the UK recently, it suffered a major electrical meltdown and was rendered immobile. It has done little more than 40,000 miles and is otherwise in first‑class condition. Is there are alternative…

Document shredder interferes with set-top box

Operating my personal document shredder crashes my digital TV set-top box, although it is 5 metres away. Toggling the on/off button on the set-top box restores normal operation.

(Sent in by Peter Cryer, 2nd February 2006.)

Lack of good PCB EMC design delays product launch

The day after attending your course on Advanced PCB Design for EMC, during which you emphasised the exponential relationship between cost of modification and the date of market introduction, I went back…

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