Analog and Digital Data

8/8/2019 Analog and Digital Data

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ANALOG AND DIGITALANALOG AND DIGITALDATADATA

Emmanuel Eilu

Faculty of Computing and IT

Makerere University

Emmanuel Eilu (Christ is Lord)


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Data acquisitionData acquisition

y Data acquisition is a process of sampling real

world physical conditions and conversion of

the resulting samples into analog signals

then to digital numeric valuesy The components of data acquisition systems

include:x Transducers and sensors

Signals Signal conditioning

DAQ hardware

Driver and application software

.



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SourcesSources

y Data acquisition begins with the physical

phenomenon to be measured. This

physical phenomenon could be the

temperature of a room, the intensity of alight source, the pressure inside a

chamber, the force applied to an object, or

many other things.



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Sensors/TransducersSensors/Transducers

y A transducer is a device that converts a

physical phenomenon into a measurable

electrical signal, such as voltage or currentx Temperature -Thermocouple, RTD, Thermistor

x Light - Photo Sensor

x Sound - Microphone

x Force and Pressure- Strain Gage Piezoelectric Transducer

x

Position and Displacement -Potentiometer, LVDT, OpticalEncoder

x Acceleration -Accelerometer

x pH -pH Electrode



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SignalsSignals

y The appropriate transducers convert physical

phenomena into measurable signals. Or Electric

or electromagnetic representations of data

y Signals can be categorized into two groups Analog

Digital



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y Analog

Analogue data transmission consists of

sending information over a physical

transmission medium in the form of

wave.

Or is the process of taking an any form

of data and translating it into electronicpulses.

Data is transmitted via a carrier wave,



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Analog transmission: WavesAnalog transmission: Waves

y Frequency (pitch)x How many times per second the waveform

repeats/oscillates

y Amplitude (volume)x The maximum height

y Phase/Periodx

How far from the beginning of the cycle (360degrees)



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Signal Representation

y Frequency

Hertz (Hz) (measure of frequency)

Kilohertz (kHz) (1,000)

Megahertz (MHz) (1,000,000) Gigahertz (GHz) (1,000,000,000)

Audio frequencies (lowest frequencies)

10/22/2010 Emmanuel Eilu (Christ is Lord)


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y Digital

Involves breaking the signal into a binary

format where the audio or video data is

represented by a series of "1"s and "0"s.

Discrete values



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y In digital technology, the analogue

wave is sampled at some interval, andthen turned into binaries that are stored

in the digital device.

y Each dot in the figure above represents

one audio sample.

On a CD, the sampling rate is 44,000 samples

per second. So on a CD, there are 44,000

numbers stored per second of music



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y An ADC is an electronic device that

converts an input analog voltage (or current

or electronic impulse) to a digital number (converts continuous signals to discrete

digital numbers.)

y

DAC is a device for converting a digital(usually binary) code to an analog signal

(current, voltage or electric impulse).



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There are two factors that determine the

quality of a digital recording

Sample ratex The rate at which the samples are captured or played back,

measured in Hertz (Hz), or samples per second. An audio

CD has a sample rate of 44,100 Hz, often written as 44 KHz

for short

Sample format or sample sizex This is the number of digits in the digital representation of

each sample.

x An audio CD has a precision of 16 bits, which corresponds

to about 5 decimal digits.



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y Digital information can be transmitted or

stored in a variety of different formatse.g computer hard disc, mini-disc, CD,

digital tape, DVD etc, etc.).


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