Differential-mode (DM) and Common-mode (CM) Wanted signals are always DM: they flow along the ‘send’ conductor, and flow back along the ‘return’ conductor(s). In single-ended signalling, all the return currents share a common conducting structure, usually the 0V of the DC power distribution system. In balanced (or ‘differential’) signalling there is a dedicated conductor for … [Read more...]
Designing and Selecting Filters: The Importance of RF Reference
The Importance of the RF Reference The RF Reference is the node on a circuit’s schematic that we define as our reference voltage when designing an RF circuit or measuring its performance. For the most cost-effective EMC, all circuits (digital, analogue, switch-mode, etc.) should now be designed using RF techniques. It is common practice to call the RF Reference ‘earth’ or … [Read more...]
Designing and Selecting Filters: How Filters Work
Ignoring all the poles and zeroes in the filter textbooks: filters work by creating an intentional discontinuity in the characteristic impedance of a current path, reflecting radio frequency (RF) energy away from a protected circuit, or absorbing the RF energy (converting it to heat) – rather like a shield does, as will be described in Part 4 of this series. The greater the … [Read more...]
5 Ways Signal Noise Can Impact Electrical Equipment
Accurate data acquisition is often critical in various engineering and technical projects. However, a pervasive yet often-overlooked issue that arises in the system is signal noise. This unwanted electrical interference, originating from multiple sources, can corrupt measurements, hinder communication, and compromise equipment integrity. Recognizing the Symptoms: … [Read more...]
Plugging into a Power Source 93 Million Miles Away
Harwin Gecko-MT 1.25mm pitch Mixed Layout Connectors Connect with confidence with Harwin’s Gecko-MT range; the smallest and lightest mixed-layout connector available for high-reliability applications. The Gecko-MT range combines the 1.25mm pitch Gecko signal connector system with mixed technology layouts, which adds 10A power contacts to the range, providing additional … [Read more...]
Selection of LC Filters to Ensure HEMP Protection of Electronic Equipment
According to military standards, passive electromagnetic LC filters of HEMP are recommended for use in all kinds of special-purpose electronic equipment. Experience gained by military specialists is usually employed when developing HEMP protection means and measures for civil equipment. Does it make sense to use extremely expensive and bulky HEMP filters for civil equipment? … [Read more...]
Doing Things That Usually Do Not Work
“If you’re not making mistakes, then you’re not doing anything.” — John Wooden Over the years, I have seen several things that make me scratch my head. Many of them are things I have done (there, I admitted it). I would like to look at these situations to (maybe) help not to make the same mistakes. So, to be clear: Do not do these things. Concerning Shielding One would … [Read more...]
EMC Confidence Checking
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...]
Key Points to Remember While Choosing PCB Assembly Company
Once you have designed a PCB and have completed everything that needs to be done before the assembly process, you would require a PCB assembly company to assemble your PCB without any problems. After all, you've been working considerably hard to assemble the layout and the design of the PCB. You would want to be convinced that your PCB gets well-assembled. To ensure that the … [Read more...]
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