See Leakage current (AC or DC) from nearby load. When a cable is connected between the two devices at different voltages, physics dictates than an electrical current must flow between the two points through the cable. Therefore, when two electrical devices are both connected to a local earth ground, there may exist a voltage difference between the two devices. ![]() For various reasons, the voltage potential between two different points on the surface of the earth is not always 0 V. The creation of an electromagnetic pulse can induce a surge that damages attached electronic devices.Īnother way ground loops affect a system is by allowing ground current to flow between devices. Larger electromagnetic energy: The antenna loop scenario can have a more damaging effect when a large current is discharged nearby. ![]() Relatively small electromagnetic energy: This could come from AC current on a nearby power cable, or RF energy transmitting through the air, and can cause electrical noise that either corrupts an analog signal or disrupts digital communications. Stray AC magnetic fields picked up in loop antenna As seen in Stray AC magnetic fields picked up in loop antenna the parallel conductive paths form an electrical loop that acts as an antenna to pick up electromagnetic energy. This will manifest as AC noise or an AC pulse. One consideration is the electromagnetically induced effect. The harm from a ground loop can be seen in different ways. Any time one of these cables connects to the same two endpoints as another cable, a ground loop is formed. These include sensors cables, communications cables, and power cables. When electrical devices are connected to a common metal chassis such as an instrument tower, the structure can create a ground path in parallel to the ground wires in sensor cables running over the structure.Ĭonductors connected to ground are found in most cables that connect to a data logger. The two paths, in this case, are the connecting cable and earth itself. In this case, two wires, one on either side of the cable shield, are connected to the ground nodes at both ends of the cable.Ī long cable connects the grounds of two electrical devices, and the mounting structure or grounding rod also directly connects the grounds of each device to the local earth ground. ![]() The drain wire of a shielded cable is connected to the local ground at both ends, and the ground is already being carried by a conductor inside the cable. Some of the common causes of ground loops include the following: When problems arise in a system, ground loops may be the source of the problems. ![]() If possible, ground loops should be avoided. Special cases exist where additional grounding helps shield noise from sensitive signals however, in these cases, multiple ground conductors are usually run tightly in parallel without conductive shielding material placed between the parallel grounds. Most often, ground loops do not have drastic negative effects and may be unavoidable. Ground loops can result in signal noise, communications errors, or a damaging flow of ground current on long cables. Multiple paths are usually associated with the ground or 0 V-potential point of the circuit. A ground loop is a condition in an electrical system that contains multiple conductive paths for the flow of electrical current between two nodes.
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