Analog to Digital Data Conversion. Kin 304 Fall 2013 Analog vs. Digital Computers use digital information Signals are continuous analog waveforms Digital.

Analog to Digital Data Conversion

Kin 304 Fall 2013

Analog vs. Digital

Computers use digital information

Signals are continuous analog waveforms

Digital information can be encoded in the analog signal

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Modulation

Digital information coded on a high frequency carrier signal

AM -Amplitude Modulation

FM – Frequency Modulation

PM – Phase Modulation

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Digital Information

BIT = BINARY DIGIT – either 1 or 0, high or low, yes or no

Decimal = Base of 10

Kin 304 Fall 2013

Base of 10

2543

1000 100 10 1

103 102 101 100

2 5 4 3

Kin 304 Fall 2013

Binary - Base of 2

41

32 16 8 4 2 1

25 24 23 22 21 20

1 0 1 0 0 1

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Bits & Bytes

Bit = Binary Digit

Byte = 8 Bits, 28 or 256 combinations

1 Kilobyte (KB) = 210 = 1024 bytes

1 Megabyte (MB) = 220 = 1,048,576 bytes

1 Gigabyte (GB) = 230 = 1,073,741,824 bytes

1 Terabyte (TB) = 240 = 1,099,511,627,776 bytes

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Components for A/D Conversion

Measurable QuantityMeasurement DeviceAnalog Signal

– Transducerstransforms one form of energy to another form

– Electrodessense biological signals

Analog Conditioning» Electronic circuitry to modify the signal

before it enters the computer for digitization.– amplification– filtering– integration

Components for A/D Conversion

Components for A/D Conversion

A/D Conversion board + software Necessary to digitize the analog

signal Sample the analog signal at a set

frequency and store it as binary information

Functions of A/D Board

Sampling– Analog signal is sampled by switching at a set frequency– Nyquist rule: at least twice frequency of signal to avoid aliasing

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Time

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e

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Signal Alias (sampling frequency too low)

Time

Vo

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e

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Functions of A/D Board

QuantitizationNumber of levels of voltage determined by the number of bits in conversion:The number of bits used to represent each conversion effects how many possible different values can be resolved from the converter...

# of Bits Possible # of Values 1 2 2 4

8 25612 4096

EncodingAssigning a digital code

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Resolution

Resolution of an A/D converterA measure of the smallest amplitude

value as a percent of full scale to which a quantity can be determined

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Voltage Range

Common ranges are:

-10v to +10v, -1v to +1v, -100mv to +100mv

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Resolution Calculation

12 bit converter, -10v to +10v

-10v to +10v = 20 v

12 bit resolution = 4096 possible values

20v / 4096 = 0.00488v per bit (4.88 mv per bit)

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A/D Software

Require A/D board compatible control software

LABVIEW– LABoratory Virtual Instrument

Engineering WorkbenchMATLAB