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Analog to Digital Data Conversion

Analog to Digital Data Conversion. Analog vs. Digital. Computers use digital information Signals are continuous analog waveforms Digital information can be encoded in the analog signal. Modulation. Digital information coded on a high frequency carrier signal AM -Amplitude Modulation

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Analog to Digital Data Conversion

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  1. Analog to Digital Data Conversion

  2. Analog vs. Digital • Computers use digital information • Signals are continuous analog waveforms • Digital information can be encoded in the analog signal

  3. Modulation • Digital information coded on a high frequency carrier signal • AM -Amplitude Modulation • FM – Frequency Modulation • PM – Phase Modulation A to D

  4. Digital Information • BIT = BINARY DIGIT • either 1 or 0, high or low, yes or no • Decimal = Base of 10 A to D

  5. Base of 10 2543 1000 100 10 1 103 102 101 100 2 5 4 3

  6. Binary - Base of 2 41 32 16 8 4 2 1 25 24 23 22 21 20 1 0 1 0 0 1

  7. 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 A to D

  8. Components for A/D Conversion • Measurable Quantity • Measurement Device • Analog Signal • Transducers • transforms one form of energy to another form • Electrodes • sense biological signals A to D

  9. Components for A/D Conversion • Analog Conditioning • Electronic circuitry to modify the signal before it enters the computer for digitization. • amplification • filtering • integration

  10. 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

  11. 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 A to D

  12. Signal Alias (sampling frequency too low) A to D

  13. Functions of A/D Board Quantitization Number 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 8 256 12 4096 Encoding Assigning a digital code A to D

  14. Resolution • Resolution of an A/D converter • A measure of the smallest amplitude value as a percent of full scale to which a quantity can be determined A to D

  15. Voltage Range Common ranges are: -10v to +10v, -1v to +1v, -100mv to +100mv A to D

  16. 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) A to D

  17. A/D Software • Require A/D board compatible control software • LABVIEW • LABoratory Virtual Instrument Engineering Workbench • MATLAB A to D

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