Electrical noise and signal to noise ratio
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Electrical noise is any undesirable electrical energy within a signal's pass band. There are several types of noise including man-made, thermal, correlated, and impulse noise. Man-made noise comes from sources like electric motors and lights. Thermal noise results from random electron motion and increases with temperature. Correlated noise is noise related to the signal, like harmonic distortion from nonlinear amplification. Impulse noise consists of short, high amplitude bursts from sources such as electric motors or lightning.
Electrical noise and signal to noise ratio
- 2. Electrical noise is defined as any undesirable electrical energy that falls with in the pass band of the signal. Example: in audio recording , any unwanted electrical signal that falls with in the audio range 0hz to 15khz will interface with the music and therefore considered as noise.
- 3. Man made noise Thermal noise Correlated noise Impulse noise
- 4. Man made noise is simply noise that is produced by mankind. The predominant sources of man made noise are spark producing mechanisms, such as commutators in electrical motors, automobile ignition systems, ac power-generating and switching equipments and fluorescent lights . Man made noise Is impulsive in nature and contains a wide range of frequencies that are propagated through space in the same manner as radio waves.
- 5. Due to random motion of electrons. It is ubiquitous (resistors, speakers, microphones, antennas, …) It is directly proportional to absolute temperature. White noise - Frequency independent up to 1013 Hz.
- 6. Impulse noise is characterized by high amplitude peeks of short duration in the total noise spectrum. It consists of sudden bursts of irregularly shaped pulses that generally last between a few micro seconds and several milliseconds, depending on their amplitude and origin. Source of impulse noise include -Electric motors -Electric lights -Automotive ignition system -Lightening
- 7. Correlated noise is noise that is correlated(mutually related)to the signal and can not be present in a circuit unless there is a signal-simply stated, no Signal , No Noise. This noise is produced by nonlinear amplification and include - Harmonic distortion and - Intermodulation distortion
- 8. This distortion occurs when unwanted harmonics of signals are produced through nonlinear amplification. Harmonics: these are integer multiples of the original signal. The original signal is the first harmonic and is the fundamental frequency. Two times the original signal frequency is the second harmonic, three times is the third harmonic and so on. This harmonic distortion is also called as amplitude distortion.
- 9. It is the generation of unwanted sum and difference frequencies produced when two or more signals are amplified in a non linear devices. The sum and difference frequencies are called cross products.
- 10. The signal is what you are measuring that is the result of the presence of your analyte Noise is extraneous information that can interfere with or alter the signal. It can not be completely eliminated, but hopefully reduced! ◦ Noise is considered random! indeterminate
- 11. It is the ratio of signal power to the thermal noise power level. s/n=ps/pn Where s/n= signal to noise power ratio Ps=signal power(watts) Pn=noise power(watts) Signal to noise power ratio is ofen expressed in db as S/N(dbs)=10 log Ps/Pn.