In part one of this post, I noted that there are three primary EMC coupling problems that are associated with the green wire safety ground: 1. The green wire conducted noise current modulates the signal and shows up as a differential voltage change across the load.2. The green wire forms a pick-up loop and acts like a magnetic field antenna.3. The green wire loop acts as a … [Read more...]
They’re Everywhere, They’re Everywhere – Part I
Read Part II here.I just finished rearranging my office. It all started with buying a new MS Windows 8 computer (that’s a story all on its own) followed closely by the failure of my printer to feed paper. So I bought a new printer, which is about two times bigger than my old one, and it wouldn’t fit in the previous location. So I moved my little flat screen TV into the old … [Read more...]
Zap – You’re Gone! A Few Truths About Lightning Safety
The last several posts have been about EM radiation hazards (RADHAZ), but there are other electromagnetic hazards. If you’ve ever been shocked by an ESD jumping from your finger to a doorknob after walking across the carpet on a cold dry winters day just imagine that incident being magnified by multiple orders of magnitude. I live in Florida and we are now winding … [Read more...]
Do We Only Believe Things that Match Our Opinion?
Whoopee! I finally got some feedback that people actually read some of the stuff I write. I received several great comments about a previous post titled: Electromagnetic Fields Don’t Exist. I’m not sure they liked what I had to say, but most were nice about it. I apparently excited some nerves. That happens when they’re exposed to electromagnetic radiation. I’m using … [Read more...]
I Can’t Believe I Just Cooked My Pinna
In the previous post, I was discussing cellphone RF safety and the fact that we really don’t know what level is safe and what’s not. Those individuals that go around with a cell phone or Bluetooth device glued to the side of their head will be happy to know that the FDA and the FCC are concerned about cell phones cooking their outer ear (the pinna). They have apparently … [Read more...]
Electromagnetic Fields Don’t Exist!
Some time ago, I made a big to-do about smart electric meters and the fact that they might be hazardous to our health. The general response I got was: you got to be kidding. Sometimes from the more heavily invested the response is: there is insufficient evidence to make that conclusion. The World Health Organization concluded that electromagnetic fields from cell phones and … [Read more...]
The Ground Loop
Several readers have made comments regarding multipoint grounding (MPG) systems. The concern is that this arrangement creates multiple ground loops. As a result, we need to address that. As some of you know, I make a lot of presentations and teach a lot of EMC seminars. A long, long time ago, I was discussing ground loops in one of my training classes … [Read more...]
Let’s Twist Again
Some time ago I introduced the equation for DM radiation from a loop. I also let Howard Johnson make fun of the single ended crowd that do not believe in loops by quoting from one of his articles. (Refer to “Why Digital Engineers Don’t Believe in EMC”, IEEE EMC Society Newsletter, Spring 1998.) The whole article is available on the internet.Anyway, to continue:E = … [Read more...]
The Hybrid Ground System
We’ve already concluded that for low frequencies the Star or SPG ground works best and at the high frequencies, the so-called equipotential ground plane with a MPG system works best. No one grounding system is perfect. On top of that, most of the equipment these days operates at frequencies from DC to daylight, so the grounding design has to cover all frequencies … [Read more...]
The Equipotential Plane That Isn’t
The success of the multipoint ground (MPG) system requires having an extremely-very-low RF impedance grounding connection to an extremely-very-low RF impedance equipotential reference plane. It also helps if the conducting materials are homogeneous and the bad things are kept separate from the good ones. Does that sound easy? You’re right – it’s not! A couple of posts … [Read more...]
