NOISES IN ELECTRONICS AND ITS PREVENTIONS

1. BY –
ASHISH JASSAL
PMPN-13

2.  Noise is considered to arise in a circuit or
measurement system from completely
random phenomena. Random phenomenas
like imperfection in electrical design.
 Coherent Noise are caused by unwanted input
signal which degrades the resolution and
accuracy of measurement systems is
considered.

3. (1) Internal noise
 Thermal noise (due to electron movement within the electrical
circuits)
 Imperfections (in the electrical design).
(2) External noise
 Natural origins (electrostatic interference and electrical storms)
 Electromagnetic interference (EMI) - from currents in cables
 Radio frequency interference (RFI) - from radio systems radiating
signals
 Cross talk (from other cables separated by a small distance)

5.  there must be three contributing factors
before an electrical noise problem can exist.
(1) A source of electrical noise
(2) A mechanism coupling the source to the
affected circuit
(3) A circuit conveying the sensitive
communication signals.

6.  Typical sources of noise are devices, which produce quick changes (spikes) in
voltage or current or harmonics, such as Large electrical motors being
switched on ,Fluorescent lighting tubes ,Solid-state converters or drive
systems ,Lightning strikes ,High-voltage surges due to electrical faults ,
Welding equipment.
Removal method-
(1) By providing adequate shielding
(2) By Providing proper grounding
with shielding
(3) Physical segregation of noise
sources from noise-sensitive
equipment

7. If a single data cable is carrying two signals, and if both the signals
have the same returning path, than the voltage drop in one channel can
transfer as noise into the other channel. the main reason for galvanic
noise is due to the interaction of a returning signal current with signals
of other channels that are moving forward.
Removal method-
(1) by using different cables
for the returning signals
(2) By providing common
grounding .
(3) Use shielded cables
and/or shielded cable
trays.
(4) Separation between the
low voltage control and
high voltage power lines:
If those lines need to
cross, they should do so
at 90° angles.

8.  Electrostatic interference is caused due transmission of noise
between various capacitances present in a circuit. As a result of high
voltage noise frequencies between the wires in the cables,
impedances are produced in the capacitances, paving way for noise
to enter into the system.
Removal method-
(1) By providing adequate
shielding
(2) By Providing proper
grounding with shielding

9. When a strong electromagnetic flux produced by a powerful conductor,
interferes with the lines of flux produced by another conductor’s
magnetic field, induces unwanted voltages
Removal method-
By using ‘twisted cables’ in
the circuit. Reduction of a
lengthy cable (conductor)
into small loops (each having
only a little area) will in turn
reduce the overall magnetic
flux of the conductor and
thus reducing its interference
and noise generating
capacities

10. This type of noise in signal cables is often
caused due to electromagnetic and electrostatic
coupling effects in the signal cable. These
coupling effects, owing to their noise voltages,
induce electromagnetic radiations in the noise
source nearby, producing RFI.
Removal method-
(1) By using proper shielding with
proper grounding

11. •Connecting all the equipment is grounded to a single point, also known
as “star” point.
•use of signal isolators/conditioners.
•Voltage signals to Conversion to current signals could benefit because a
shielded twisted pair of conductors can transmit a 4-20 mA signal over
very long distances. Earth grounding the shield at one end will help
provide protection against electrical noise.
•Separating signal and power in a cable run.