Reducing Interference: Shielding and Grounding

In course

Description

This lecture covers the importance of differential measurement in reducing interference, the role of shielding and grounding in protecting signals, the concept of guarding the input to prevent leakage currents, the use of shielded cables and pairs to reduce RF coupling, methods for breaking ground loops, and the significance of decoupling power supply to minimize AC impedance. Examples for shielding bioelectrodes are also discussed, emphasizing the need for extensive shielding. The instructor highlights the fundamental nature of noise in resistive systems, the impact of interference from preamplifiers, and ways to mitigate noise through proper amplification, bandwidth reduction, and interference reduction techniques.

Instructors (2)

Official source

https://mediaspace.epfl.ch/media/0_2mdq33ql

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Related concepts (14)

Electromagnetic shielding

In electrical engineering, electromagnetic shielding is the practice of reducing or blocking the electromagnetic field (EMF) in a space with barriers made of conductive or magnetic materials. It is typically applied to enclosures, for isolating electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs (). Electromagnetic shielding that blocks radio frequency (RF) electromagnetic radiation is also known as RF shielding.

Electromagnetic interference

Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.

Shielded cable

A shielded cable or screened cable is an electrical cable that has a common conductive layer around its conductors for electromagnetic shielding. This shield is usually covered by an outermost layer of the cable. Common types of cable shielding can most broadly be categorized as foil type (hereunder: metallised film), contraspiralling wire strands (braided or unbraided) or both. A longitudinal wire may be necessary with dielectric spiral foils to short out each turn.

Twisted pair

Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighbouring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander Graham Bell. For additional noise immunity, twisted-pair cabling may be shielded.

Power cable

A power cable is an electrical cable, an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. Power cables that are bundled inside thermoplastic sheathing and that are intended to be run inside a building are known as NM-B (nonmetallic sheathed building cable).