Ground Loops
editThis document still has some serious flaws. For example, in the last diagram the claim is made that if only one point is grounded between two pieces of gear, a ground loop is avoided.
This presentation Ground Loops Hifisonix shows why this is not the case. Slides 6 through 12 show the 'line diagram' technique in which the signal ground and safety ground are highlighted to delineate the total loop area. From this you can quickly ascertain that any magnetic field impinging on the loop in the said diagram will generate a current in the shield. Whether a balanced signal or not is used, there will still be a ground loop current flowing in the shield and if there happens to be more than one ground connection to the chassis at either end, the result will almost certainly be ground loop noise of some description. So, to get it right in this particular case, the interconnect would have to be balanced and there must be one and only one connection to the equipment chassis either end.
For a complete rewrite, its best to start with an outline - thrashing this out will take some weeks, but once its done, the details can be filled in and the result will be a coherent document. Here is a suggested framework to kick things off with:-
Definition of a ground loop and more widely 'noise loops' since this will then allow a discussion about HF noise loops in equipment
Understanding the difference between signal ground and safety ground (people mix the two up and make other errors - eg see earlier comment above)
How do ground loops manifest - audible noise in audio systems, erroneous readings/signals in instrumentation systems
What causes a ground loop - magnetic induction, potential differences in ground points within a system, HF electric field coupling
Different types of ground loop - classic magnetic field induced ground loop, leakge ground loop (leakage current always < RCD trip current), cross channel ground loop, HF electric field coupled ground loop (usually caused by SMPSU's or other HF sources)
Ground Loops/noise loops in systems with safety grounds vs double insulated systems where no safety ground is present
Mitigating AC ground loops in audio equipment
Mitigating Cross channel ground loops in audio equipment
Physical wiring, layout and cable routing best practises for low noise
Using ground lifters (with safety warning) balanced signal interconnects, signal isolation techniques using eg transformers in audio systems, or isolation amplifiers in instrumentation systems
Brief discussion about cost vs complexity re the above
Technique's for identifying ground loop related issues - use of line diagrams
There should be a discussion about this framework before writing the detail actually starts.This article should reference (ie link to) separate articles on Radio Frequency Interference and then another one on common impedance coupling.
At this stage, I don't think the equations shown in the original entry add any value - in fact they detract from the entry in my view. Although ground loops are simple enough to understand conceptually, in practice they can be extremely complex due to the multitude of coupling loops and the coupling at LF and HF which will be different. Further, since the induced loop current flows will be highly dependent upon the frequency, this adds a further layer of complexity which cannot be covered by a few simple equations. The article should reference Maxwell's equations and magnetic/electric field coupling for a more robust and scientific treatment of the subject by experts in those fields. Harrison Thomas 19:55, 30 January 2023 (UTC)