Shields are your friend, except when…

Shields are your friend, except when… article tells that engineers just love to put shields on circuits, mostly as a defensive measure against signals on the outside getting into and disturbing our circuits, but they also keep signals inside from getting out and this really makes the folks responsible for EMI compliance happy. Even on

Ground Loop Tutorial

I was just pointed to a new interesting ground loop document few days ago. Ground Loop Tutorial is a tutorial on electrical interference with emphasis on ground loops. It distinguishes several different types of interference and discusses the underlying physics at a basic level. In the end there is a good list of Methods for

Noise Reduction and Isolation in Measurement

Grounding, or connecting some part of an electrical circuit to ground ensures safety for personnel and it usually improves circuit operation. Unfortunately, a safe environment and a robust ground system often do not happen simultaneously. It takes planning based on systematically understanding how electricity behaves in various types of circuits. Preventing electrical shocks and electrical

Understanding grounding, shielding, and guarding

Inadequate shielding and bad grounding are often blamed when measurements are inaccurate, especially in high-impedance applications. Understanding grounding, shielding, and guarding in high-impedance applications article tells tells that in fact, shielding and grounding problems are frequently responsible for measurement errors, but many test system developers aren’t quite sure why. Many measurement errors can be traced

HDMI and ground loops

In my Audio and video signal susceptibility classes I wrote that digital video interfaces like DVI and HDMI can also have ground loop noise problems as they use a combination of balanced and unbalanced signals. Ground loop problem is one very possible source of intermittent problems over long distance in HDMI installations. This article is

Balanced Line Technology

Balanced inputs and outputs have been used for many years in professional audio, but profound misconceptions about their operation and effectiveness still survive. Conventional wisdom about them is sometimes wrong. Balanced Line Technology web page gives you a good look at the balanced line technology in audio applications. The balanced line technology is also applicable

EMF measurements

An electromagnetic field (also EMF or EM field) is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature. EMF measurement

Audio and video signal susceptibility classes

My article Signal reference grids in the data center shows that different types of data communication interfaces are classified into susceptibility classes: Data communication interface classification Susceptibility class: Low immunity Interfaces in class: Parallel ports, RS-232 ports, Proprietary back-plane, Video cables Characteristics: Copper cabling with ground referenced signals. Any shift in ground voltage between the

Mains power isolation for ground loop solving

It is sometimes suggested that a mains power isolation transformer might be used to solve the ground loop problem. It is true, that many times a mains isolation transformer does help, but not always. A system with properly used isolation transformer is still safe, it can be even safer than system without isolation transformer. Remember