GROUP MEMBERSGROUP MEMBERS0F GROUP 70F GROUP 7

Mr.Syed Ahmad Sobrie B Syed Ramli Mr.Syed Ahmad Sobrie B Syed Ramli (Leader) (Leader)

Ms.Noor Ropidah Bt Bujal (Secretary)Ms.Noor Ropidah Bt Bujal (Secretary)

Ms.Tuan Nor Balkhis Bt Tuan HarunMs.Tuan Nor Balkhis Bt Tuan Harun

Mr.Rajes Kanna A/L Seluwmuthu Mr.Rajes Kanna A/L Seluwmuthu

Mr.Mohd Aizuddin B AbdullahMr.Mohd Aizuddin B Abdullah

Mr.Mohd Shariman B A.AzizMr.Mohd Shariman B A.Aziz

NOISENOISE

INTRODUCTIONINTRODUCTION

Noise is unwanted Noise is unwanted electrical or electrical or electromagnetic electromagnetic energy that degrades energy that degrades the quality of signals the quality of signals and dataand data.  . 

Noise can be divided Noise can be divided into 2 general into 2 general categoriescategories

a.a. Correlated noiseCorrelated noise

implies relationship implies relationship between the signal and between the signal and the noise, exist only the noise, exist only when signal is presentwhen signal is present

b.b. Uncorrelated noiseUncorrelated noise

present at all time, present at all time, whether there is signal whether there is signal or not. or not.

i) Internal noisei) Internal noise

ii) External noiseii) External noise

Noise occurs in digital Noise occurs in digital and analog systems, and analog systems, and can affect files and can affect files and communications and communications of all types, including of all types, including text, programs, text, programs, images, audio, and images, audio, and telemetry.telemetry.

UNCOLERATED NOISEUNCOLERATED NOISE

External noiseExternal noise

∑ Generated outside Generated outside the device or circuitthe device or circuit

a. Atmospherica. Atmospheric

b. Extraterrestrialb. Extraterrestrial

c. Man madec. Man made

Internal noiseInternal noise

∑ Generated within a Generated within a device or circuit.device or circuit.

a. Shot noisea. Shot noise

b. Transit-time noiseb. Transit-time noise

c. Thermal noisec. Thermal noise

CORRELATED

FACTS

UNCORRELATED

CORRELATED

HARMONIC DISTORTION {HT}

INTERMODULATIONDISTORTION {ID}

UNCORRELATED

EXTERNAL INTERNAL

ATHMOSPHERIC

MAN-MADE

IMPULSE

INTERFERENCE

SHOT THERMAL

TRANSIENTTIME

NOISE NOISE REDUCTION REDUCTION TECHNIQUESTECHNIQUES

Techniques on How To Techniques on How To Eliminated or Reduces Eliminated or Reduces

NoiseNoiseSignal FilteringSignal Filtering often used in eddy current testing to often used in eddy current testing to

eliminate unwanted frequencies from the eliminate unwanted frequencies from the receiver signal.receiver signal.

while the correct filter settings can while the correct filter settings can significantly improve the visibility of a defect significantly improve the visibility of a defect signal, incorrect settings can distort the signal signal, incorrect settings can distort the signal presentation and even eliminate the defect presentation and even eliminate the defect signal completely.signal completely.

filtering is applied to the received signal and, filtering is applied to the received signal and, therefore, is not directly related to the probe therefore, is not directly related to the probe drive frequency.drive frequency.

Filters EffectsFilters Effects The HPF allows high frequencies to pass and filters The HPF allows high frequencies to pass and filters

out the low frequencies.out the low frequencies. The LPF allows low frequency to pass and filters out The LPF allows low frequency to pass and filters out

the high frequency.the high frequency. First filtered out with a HPF and then high First filtered out with a HPF and then high

frequency electronic noise was filtered with a LPF to frequency electronic noise was filtered with a LPF to leave a clearly visible flaw indication.leave a clearly visible flaw indication.

It should also be noted that since flaw indication It should also be noted that since flaw indication signals are comprised of multiple frequencies, both signals are comprised of multiple frequencies, both filters have a tendency to reduce the indication filters have a tendency to reduce the indication signal strength.signal strength.

Additionally, scan speed must be controlled when Additionally, scan speed must be controlled when using filters.using filters.

Scan over a flaw too slow and the HPF might filter Scan over a flaw too slow and the HPF might filter out the flaw indication. Scan over the flaw too fast out the flaw indication. Scan over the flaw too fast and the LPF might eliminate the flaw indication.and the LPF might eliminate the flaw indication.

Refers to various Refers to various techniques for improving techniques for improving the accuracy and reliability the accuracy and reliability of digital communications.of digital communications.

Basically, DSP works by Basically, DSP works by clarifying, or standardizing, clarifying, or standardizing, the the levelslevels or or statesstates of a of a digital signal.digital signal.

A DSP circuit is able to A DSP circuit is able to differentiate between differentiate between human-made signals, human-made signals, which are orderly, and which are orderly, and noise, which is inherently noise, which is inherently chaotic.chaotic.

If an incoming signal is If an incoming signal is analog, for example a analog, for example a standard television standard television broadcast station, the broadcast station, the signal is first converted signal is first converted to digital form by an to digital form by an analog-to-digital analog-to-digital converter (ADC)converter (ADC)..

The DSP circuit adjusts The DSP circuit adjusts the levels of the resulting the levels of the resulting digital signal so they are digital signal so they are at the correct values.at the correct values.

Digital Signal ProcessingDigital Signal Processing

We arranged a burstWe arranged a burst

noise eliminatingnoise eliminating

equipment andequipment and

characterized thecharacterized the

1/f and burst noises1/f and burst noises

In some electronicIn some electronic

materials,componenmaterials,componentsts

the electric contactsthe electric contacts

and bipolarand bipolar

transistorstransistors

Burst Noise Eliminating Burst Noise Eliminating EquipmentEquipment

A ground is a conducting A ground is a conducting flow path for current flow path for current between an electric circuit between an electric circuit and the earth. Ground and the earth. Ground wires are typically made wires are typically made with materials that have with materials that have very low resistance. Ground very low resistance. Ground wires also safeguard wires also safeguard against unwanted common-against unwanted common-mode signals and prevent mode signals and prevent accidental contact with accidental contact with dangerous voltages. Return dangerous voltages. Return lines carry power or signal lines carry power or signal currents.currents.

Analog Signal Analog Signal Transmission (Noise and Transmission (Noise and Grounding)Grounding)

The second ground is for the signal ground. This The second ground is for the signal ground. This ground is necessary to provide a solid reference ground is necessary to provide a solid reference for the measurement of all low-level signals. It is for the measurement of all low-level signals. It is very important that this ground is grounded very important that this ground is grounded separate and isolated from the system ground. In separate and isolated from the system ground. In a single-point ground configuration, minimal a single-point ground configuration, minimal current can flow in the ground reference. current can flow in the ground reference.

LEARNING ISSUESLEARNING ISSUES Noises are every Noises are every

where.where. Noise can’t be Noise can’t be

eliminated but can be eliminated but can be reduced. reduced.

Noise comes from Noise comes from many sources that many sources that related to related to communications communications transmission.transmission.

Certain techniques Certain techniques of reducing noise of reducing noise can be used by can be used by certain noise.certain noise.

The longer the The longer the length of length of transmission the transmission the higher the noises higher the noises are.are.

CONCLUSIONCONCLUSION

Noise is unwanted electrical or Noise is unwanted electrical or electromagneticelectromagnetic

energy that occurs during data and signals energy that occurs during data and signals

transmission. It can not be eliminated but transmission. It can not be eliminated but cancan

be reduce with several reduction techniques be reduce with several reduction techniques forfor

several noise.several noise.