Ground Loop?

Question

I need a Plain Jane explination of a ground loop.
I am a visual learner and have no visual to learn. so explain it to me for how it looks.

This is MECP study guide explanation:
Ground Loops result when all the components in an audio system do not see exactly the same ground. huh?

Differences in degrees of being grounded are called ground potential. huh?

Again please explain in how it looks to the eye, then explain the deffinitions I just gave you.

Also is a ground loop a bad thing?

(this is for car audio by the way)

Answer 1

You might try this link.
http://www.google.com/imgres?imgurl=http://zone.ni.com/cms/images/devzone/tut/1fig_high.gif&imgrefurl=http://zone.ni.com/devzone/cda/tut/p/id/5358&h=230&w=371&sz=6&hl=en&start=2&tbnid=SQKMmi36L2zGDM:&tbnh=76&tbnw=122&prev=/images%3Fq%3DGround%2BLoops%2Bresult%2Bwhen%2Ball%2Bthe%2Bcomponents%2Bin%2Ban%2Baudio%2Bsystem%26svnum%3D50%26hl%3Den%26rlz%3D1B3GGGL_en___US231


Ground Loops
Ground loops are the most common source of noise in data acquisition applications. They occur when two connected terminals in a circuit are at different ground potentials, causing current to flow between the two points. The local ground of the system can be several volts above or below the ground of the nearest building, and nearby lightning strikes can cause the difference to rise to several hundreds or thousands of volts. This additional voltage itself can cause significant error in the measurement, but the current that causes it can couple voltages in nearby wires as well. These errors can appear as transients or periodic signals. For example, if a ground loop is formed with 60 Hz AC power lines, the unwanted AC signal appears as a periodic voltage error in the measurement.

When a ground loop exists, the measured voltage, Vm, is the sum of the signal voltage, Vs, and the potential difference, Vg, which exists between the signal source ground and the measurement system ground, as shown in Figure 1. This potential is generally not a DC level; therefore, the result is a noisy measurement system, often showing power-line frequency (60 Hz) components in the readings.


Figure 1. A Grounded Signal Source Measured with a
Ground-Referenced System Introduces Ground Loop
http://zone.ni.com/cms/images/devzone/tut/1fig_high.gif
To avoid ground loops, ensure that there is only one ground reference in the measurement system, or use isolated measurement hardware. Using isolated hardware eliminates the path between the ground of the signal source and the measurement device, therefore preventing any current from flowing between multiple ground points.

Hope it helps.

Answer 2

A ground loop is simply a spin of the aircraft on the ground, wherein it turns around to face backwards, or at least turns a lot so that it's no longer pointing the way it should. It's usually the fault of the pilot, who makes a mistake in steering the aircraft on the ground, or in handling the rollout after landing. It's much more common in tail-dragger aircraft (with two big wheels in front and one tiny wheel on the tail) than in aircraft with tricycle-style gear (one small nosewheel and two big wheels in the back). Since most aircraft have tricycle landing gear today, ground loops are not as common as they used to be. If the spin is violent enough, the aircraft may tip to one side, dig a wing into the ground, or even flip over, so ground loops can be dangerous. More often they are simply embarrassing and sometimes expensive (if the aircraft is damaged).

Answer 3

A ground loop is where you have two audio components connected together (like with audio cables), but that have their power supply grounds at a different ground potential.

In a car audio system, this could be caused by components having different ground attachment points, where one of the grounds doesn't make as good of contact as the other (a little more resistance to ground). So some of the current that is running the component with the poor ground is running through the audio cables connecting them and through the component with the good ground.

This could cause excessive current through the component with the good ground. Or it could cause floating voltages through the component with the good ground, resulting in damage to that component.

If you have a ground loop in your home wiring and connect audio components together, the result will be an audible 60-cycle hum that is especially noticeable when there is no audio signal at the time (between songs on a CD, for example).

Answer 4

http://www.epanorama.net/documents/groundloop/basics.html