Understanding Electrical Ground Loops
An electrical ground loop occurs when there are two or more paths to ground in an electrical system, creating an unintended closed circuit. This unwanted circuit can allow current to flow through the ground connections, leading to voltage differences at different 'ground' points and introducing noise or interference into signals.
How Ground Loops Form
Ground loops typically form when different pieces of electronic equipment are connected to each other, and each piece also has its own connection to the electrical ground through a power outlet or chassis. If these ground connections are made at different physical points, small differences in electrical potential between these points can cause current to flow, forming the 'loop'.
Consequences of a Ground Loop
The most common consequence of a ground loop is the introduction of audible hum or buzz in audio systems, often at the power line frequency (e.g., 50 or 60 Hz). In video systems, they can cause rolling bars or other visual artifacts. In digital or sensor systems, ground loops can corrupt data, reduce measurement accuracy, or lead to erratic behavior, as noise is superimposed onto the intended signals.
Preventing and Mitigating Ground Loops
Preventing ground loops often involves ensuring a single, central ground point for all interconnected equipment, known as 'star grounding'. Other techniques include using isolation transformers, optical isolators (for data signals), or balanced audio cables, which are designed to reject common-mode noise associated with ground potential differences.