Noise/Interference 1) Noise in the recording system 2) - - PowerPoint PPT Presentation

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Oct 19, 2023 287 likes •434 views

Noise/Interference 1) Noise in the recording system 2) Electrical interference AC power lines, radio &TV transmitters, fluorescent lights, computers, mechanical vibrations, etc. The signal to noise ratio is

SLIDE 1

Noise/Interference

1) Noise in the recording system
2) Electrical interference
AC power lines, radio &TV transmitters, fluorescent lights,

computers, mechanical vibrations, etc. The signal to noise ratio is what’s important.

SLIDE 2

Real noise Oscilloscope screen Real Noise

1) Thermal Agitation V2 = 4kTRf
2) Shot noise

Circuit noise

SLIDE 3

Power line- (most common Magnetic pick up Real noise Transient power surge Electro- magnetic radiation Types of Interference:

Electrostatic
Electromagnetic
Electromagnetic radiation

Signal interference (periodic)

SLIDE 4

Electrostatic noise Stationary capacitance

SLIDE 5

Electrostatic Coupling

I = C dv/dt
V= RC dv/dt

Solution: 1) Keep power lines far from recording leads

2) Surround conductors with grounded metallic
surface
3) Sometimes have to unplug a device

BNC Cable

SLIDE 6

Electrostatic coupling solution

SLIDE 7

Magnetic pick up Electromagnetic coupling

SLIDE 8

Electromagnetic coupling

SLIDE 9

Electromagnetic coupling solution

SLIDE 10

Grounds at different levels Solution

SLIDE 11

Electromagnetic Radiation- high frequency, can be flitered

SLIDE 12

SLIDE 13

Summary

1) Carry out the experiments in a grounded enclosure.
2) Ground all metallic objects passing through the cage and

enclose all wiring in a grounded wire shield.

3) Make the leads between the amplifier and preparation as

short and direct as possible. Twist input leads together.

4) Avoid ground loops.