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This module will cover the basics of sampling theory and Analog to Digital Converters (ADC).

Sampling refers to the process of converting a continuous, analog signal to discrete digital numbers. Typically, an Analog to Digital Converter (ADC) would be used to convert voltages to a digital number corresponding to a certain voltage level.

This shows the way that a given analog signal might be sampled. The frequency at which the signal is sampled is known as the sampling rate .

Resolution

The number of bits used to represent a sampled, analog signal is known as the resolution of the converter. This number is also related to the total number of unique digital values that can be used to represent a signal.

For example, if a given ADC has a resolution of 12 bits, then it can represent 4,096 discrete values, since 2^12 = 4,096; if the resolution is 16 bits, it can represent 65,536 discrete values.

We may also think about resolution from an electrical standpoint, which is expressed in volts. In that case, the resolution the ADC is equal to the entire range of possible voltage measurements divided by the number of quantization levels. Voltage levels that fall outside the ADC’s possible measurement range will saturate the ADC. They will be sampled at the highest or lowest possible level the ADC can represent.

For example, ADC specifications could be as follows:

  • Full scale measurement range: -5 to 5 volts
  • ADC resolution 12 bits: 2 12 4,096 quantization levels
  • ADC voltage resolution is: 5V -5V 4096 0.0024 V 2.4 mV

Large ranges of voltages will fall into in a single quantization level, so it is beneficial to increase the resolution of the ADC in order to make the levels smaller. The accuracy of an ADC is strongly correlated with its resolution however; it is ultimately determined by the Signal to Noise Ratio (SNR) of the signal. If the noise is much greater relative to the strength in the signal, then it doesn't really matter how good or bad the ADC is. In general, adding 1 more bit of resolution is equal to a 6 dB gain in SNR.

Sampling rate

Analog signals are continuous in time. In order to convert them into their digital representation we must sampled them at discrete intervals in time. The interval at which the signal is captured is known as the sampling rate of the converter.

If the sampling rate is fast enough, then the stored, sampled data points may be used to reconstruct the original signal exactly from the discrete data by interpolating the data points. Ultimately, the accuracy of the reconstructed signal is limited by the quantization error, and is only possible if the sampling rate is higher than twice the highest frequency of the signal. This is the basis for the Shannon-Nyquist Sampling Theorem . If the signal is not sampled at baseband then it must be sampled at greater than twice the bandwidth.

Aliasing will occur if an input signal has a higher frequency than the sampling rate. The frequency of an aliased signal is the difference between the signal's frequency and the sampling rate. For example, a 5 kHz signal sampled at 2 kHz will result in a 3 kHz. This can be easily avoided by adding a low pass filter that removes all frequency higher than the sampling rate.

Questions & Answers

are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
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Google
da
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Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
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ya I also want to know the raman spectra
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Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
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analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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Source:  OpenStax, Introduction to the texas instruments ez430. OpenStax CNX. Jun 19, 2006 Download for free at http://cnx.org/content/col10354/1.6
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