Analog and digital data

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Analog and digital data
Skills none IT concepts analog to digital
conversion, digital to analog conversion, sample
rate, sample size, quality-file size trade off
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2
Where does this topic fit?

• Internet concepts
• Applications
• Technology
• Implications
• Internet skills
• Application development
• Content creation

3
Digital and analog clocks
Start clocks
Which clock is digital? Which analog? Which
clock is the closest analog to the physical world?
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A digital clock
120000 120001 120002 120003 etc.
Digital data is discreet and jumpy, not smooth
and continuous
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Physical sensors ? electric signals
Light level Pressure Sound waves Acceleration Posi
tion of a knob Orientation Proximity Gasses in
the air Magnetic field
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For example, a microphone
Varying voltage
Sound waves
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Computers require digital data
Computer
10010110 (150) 11001001 (201) 11000111 (199)
Analog to digital converter
Analog data
Digital data
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The input is continuous, analog data
Sample the signal at regular intervals
v2
v1
v7
. . .
. . .
S7
S3
S1
S2
9
Each sample produces a number
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Each sample produces a number
A jagged approximation of the original,
continuous signal
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More frequent sampling results in a better fit
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Each sample produces a number But How big (how
many bits) is each number?
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What time is it between seconds?
Round off to the nearest second
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60 steps
More steps (higher resolution) means smaller
round-off errors
12 steps
4 steps
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Digitizing introduces round-off errors
5
4
3.6
3
2.2
2
1
0
16
3
More steps (intervals) between the minimum and
maximum values means smaller round-off errors
0
7
0
15
0
17
More bits per sample ? more possible steps
Number of bits Number of possible steps
1 2
2 4
3 8
4 16
5 32

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The quality/file size tradeoff
Increase sample rate ? quality ? file size
? Increase sample size ? quality ? file size ?
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Computers can output analog data
Computer
10010110 (150) 11001001 (201) 11000111 (199)
Digital to analog converter
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Generate a somewhat jagged analog signal by
approximating the value between samples with
straight lines
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Electric signals ? change physical world
Sound Light Flow rate Temperature Turn things on
and off

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A few questions
The value of sample 9 would be between the values
of which two samples?
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Without looking back, what two factors determine
the quality or goodness of fit of a digitized
signal to the original analog signal?
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Where does this topic fit?

• Internet concepts
• Applications
• Technology (electronics)
• Implications
• Internet skills
• Application development
• Content creation