I was recently working with a manufacturer of stand-alone ticket machines, who had big problems with Ethernet-related emissions. Long story short – it was the Ethernet hub they had incorporated in their machine. They had assumed that all CE-marked Ethernet hubs would be equally good for EMC, and they had several different types lying around their design department. We tested … [Read more...]
Mains Harmonic Current Emissions are Always Bad – It is Risky to Rely on the Limits or Exclusions in the Standards
Many (perhaps all) of EMC standards that are listed under the EMC Directive, that set limits for mains harmonic emissions, have exclusions (‘let-outs’) for certain types of equipment, especially: (these examples are from IEC/EN 61000-3-2 Ed.5:2018) Lighting equipment with a rated power of less than but not equal to 5W Equipment with a rated power of 75W or less, e.g. … [Read more...]
ESD Testing Needs to Change to Reflect Real-Life
Semiconductor die shrinking means that 0.7ns risetimes are now too slow Electrostatic discharges in the real world cover a very wide range: from relatively slow high-voltage events (say, > 1kV peak) to extremely fast low-voltage events (say, < 1kV peak). The figure shown is of the transient field radiated by a micro-gap discharge between two coins – more on this … [Read more...]
Ground / Power Bounce Cause Noise Emissions From All IC Pins
Ground and power bounce are often ignored as sources of CM noise emitted from all integrated circuit (IC) pins, even if they are static inputs or outputs, digital or analogue, and even sometimes emitted as radiated noise directly from the body of the IC (especially when its physical structure resonates). CMOS ICs use ‘totem-pole’ logic switching gates that momentarily short … [Read more...]
Risks Associated with EMC and EMI – Don’t get Confused!
There are many kinds of risk For example: the risk of being late for an appointment; the risk of buying a lottery ticket but not winning a prize; the risk of designing and manufacturing a new product that might not sell well enough, etc. The above are examples of non-safety-related risks, but safety-related risks also exist. EMC1 Risk Management (or, the Risk Management … [Read more...]
A Simple Method for Estimating Radiated Emissions – Part 2
I recently published this blog, detailing a simple proven method for estimating the radiated E field with specified test setup. As a result, I received the following feedback... 'This model is wrong for equipment tested over a ground plane as described. The complex correct transmission line model (less the ground plane) is given by Balanis, and a simpler but accurate … [Read more...]
A Simple Method for Estimating Radiated Emissions
A simple method for estimating radiated emissions I recently received the following question: How to calculate the radiated E field with following test conditions with an antenna placed 1 meter away from the test setup?: A commercial equipment under test with metal housing Equipment placed on the grounded metallic table/plane LISN installed (and also placed … [Read more...]
Don’t Rely on the Stability of the Mains Frequency
My old colleague and good friend Tim Williams sent me the story below for inclusion in EMI Stories/Banana Skins, and I found it so interesting in so many ways that I decided to publish it as a Blog. In so very many EMC standards and other meetings on EMC, we hear that the stability of the AC mains power frequency is either ‘not an EMC issue’ or is ‘never a real EMC … [Read more...]
EMC Question for 400Hz Power System
Question: I would appreciate it if you could provide your view / share your expertise on the EMC/EMI protection requirements between the 400Hz Ground Power Systems and the various ICT/ELV installations within an Aircraft. Answer: An interesting and important question! And much too big an issue to be able to deal with comprehensively, in a blog post. The … [Read more...]
Under the Medical Safety Standard IEC 60601-1-1:2014 an EMC Test Lab is not Required to Assess or Review Any Aspect of a Risk Management File
Note: This content was originally posted in January 2020 on emcstandards.co.uk. IEC 60601-1-2:2014 is a medical device safety standard that deals with safety risks that can be caused by electromagnetic interference with electronics. It is not an EMC compliance standard! If the EMC test lab has the necessary safety risk assessment competencies, they could review/assess the … [Read more...]
