The circuit diagram illustrates a simple ground loop. Simplified circuit illustrating a ground loop. One is the normal safety ground that connects to exposed metalwork, the other is a technical ground for cable screens and the like.
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For this reason, in some large professional installations such as recording studios, it is sometimes the practice to provide two completely separate ground connections to equipment bays. Proper design of such a system will satisfy both safety grounding requirements and signal integrity.
Ground loops can also exist within the internal circuits of electronic equipment, as design flaws.Īddition of signal interconnection cables to a system where equipment enclosures are already required to be bonded to ground can create ground loops. In computer cables it can cause slowdowns or failures of data transfer.
In a video system it may cause distortion or syncing problems. In audio equipment, the 50 or 60 Hz interference may be heard as a hum in the speakers. This is added to the signal applied to the input of the next stage. The induced alternating current flowing through the resistance of the cable ground conductor will cause a small AC voltage drop across the cable ground. Since the ground conductor of the signal cable linking the two devices is part of the signal path of the cable, the alternating ground current flowing through the cable can introduce electrical interference in the signal. Since the conductors comprising the ground loop usually have very low resistance, often below one ohm, even weak magnetic fields can induce significant currents. The presence of high-power equipment such as industrial motors or transformers can increase the interference. The amount of current induced will depend on the magnitude and proximity of nearby currents. The ground loop acts as a single-turn secondary winding of a transformer, the primary being the summation of all current-carrying conductors nearby. These ambient magnetic fields passing through the ground loop will induce a current in the loop by electromagnetic induction. In the vicinity of electric power wiring there will always be stray magnetic fields, particularly from utility lines oscillating at 50 or 60 hertz. This forms a closed loop through the ground conductors of the power cords, which are connected through the building wiring. When signal cables are connected between both devices, the shield of the signal cable is typically connected to the grounded chassis of both devices. A common example is two electrical devices each connected to a mains power outlet by a 3 conductor cable and plug containing a protective ground conductor for safety. ( January 2017) ( Learn how and when to remove this template message)Ī ground loop is caused by the interconnection of electrical devices that results in multiple paths to ground, thereby forming closed conductive loops through the ground connections. Unsourced material may be challenged and removed. Please help improve this section by adding citations to reliable sources. Removal of safety ground connections to equipment in an effort to eliminate ground loops also eliminates the protection the safety ground connection is intended to provide. The use of differential signaling can provide rejection of ground-induced interference. Wiring practices that protect against ground loops include ensuring that all vulnerable signal circuits are referenced to one point as ground. Ground loops are a major cause of noise, hum, and interference in audio, video, and computer systems. Current may be produced in a circular ground connection (ground loop) by electromagnetic induction. This is typically caused when enough current is flowing in the connection between the two ground points to produce a voltage drop and cause two points to be at different potentials. In an electrical system, a ground loop or earth loop occurs when two points of a circuit are intended to have the same ground reference potential but instead have a different potential between them. ( July 2014) ( Learn how and when to remove this template message) Please help improve it to make it understandable to non-experts, without removing the technical details. This article may be too technical for most readers to understand.
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