Analogue to Digital Conversion Concepts
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Questions and Answers

What does quantisation error represent in digital data conversion?

  • The sum of all bits used in storage
  • The total number of transducers used
  • The average of all sampled values
  • The absolute difference between stored and original values (correct)

    • In pulse code modulation, which aspect is most dependent on the sampling rate?

  • The bit depth used for quantisation
  • The number of transducers required
  • The amount of power consumed by the system
  • The accuracy of the signal reconstruction (correct)

    • Which statement best describes the Nyquist Theorem?

  • The theorem is only applicable to audio signals.
  • It defines the minimum number of transducers needed for conversion.
  • It states that the maximum sampling rate is double the highest frequency of the signal. (correct)
  • It quantifies the quantisation error in the process.

    • Increasing quantisation levels in a digital system will primarily result in what?

    <p>Improved accuracy of the representation</p> Signup and view all the answers

    Which of the following best describes the function of an ADC in a microprocessor system?

    <p>To transform analogue signals into digital data</p> Signup and view all the answers

    What is the primary consequence of insufficient sample rates according to the Nyquist theorem?

    <p>Loss of data integrity</p> Signup and view all the answers

    Which of the following best describes Pulse Code Modulation (PCM)?

    <p>It stores each sample as a binary integer</p> Signup and view all the answers

    Which statement accurately reflects the concept of quantisation in digital signal processing?

    <p>It converts continuous amplitude values into discrete levels</p> Signup and view all the answers

    According to the Nyquist theorem, what is the minimum sampling rate required if the maximum frequency (Fmax) of a signal is 20 kHz?

    <p>40 kHz</p> Signup and view all the answers

    What is the impact of a high quantisation level on a signal's quality?

    <p>Improves signal fidelity</p> Signup and view all the answers

    How does the sample rate of 44.1 kHz for CD-quality audio correspond to potential signal frequencies?

    <p>It captures frequencies up to 22.05 kHz only</p> Signup and view all the answers

    What defines an optimal sampling frequency for a given signal?

    <p>It needs to be at least twice the highest frequency component</p> Signup and view all the answers

    Which sampling rate is most appropriate for capturing telephone speech effectively?

    <p>8 kHz</p> Signup and view all the answers

    What is the relationship between the number of bits (N) in an analogue-to-digital converter (ADC) and the number of quantisation levels?

    <p>The number of levels is equal to 2^N.</p> Signup and view all the answers

    How is the resolution (R) of an ADC defined?

    <p>R = VREF / 2N</p> Signup and view all the answers

    What is the maximum quantisation error in a 3-bit ADC?

    <p>+/- R/2</p> Signup and view all the answers

    Which equation represents the dynamic range (DR) of an N-bit ADC?

    <p>DR = 6.02N + 1.76 dB</p> Signup and view all the answers

    In terms of quantisation levels, what happens when an ADC has non-uniform quantisation?

    <p>Some quantisation levels are closer together than others.</p> Signup and view all the answers

    Which of the following best describes Pulse Code Modulation (PCM)?

    <p>A way to convert analogue signals into a digital format through sampling, quantisation, and encoding.</p> Signup and view all the answers

    According to Nyquist Theorem, what is the minimum sampling rate required to avoid aliasing?

    <p>Twice the signal frequency.</p> Signup and view all the answers

    What does an increase in the number of bits (N) in an ADC primarily affect?

    <p>The quantisation levels and resolution.</p> Signup and view all the answers

    Study Notes

    Quantisation

    • Defines how a value is stored in binary
    • CD-quality audio: 16-bits
    • Recorded speech: 8- or 12-bits
    • Quantisation is necessary for single values too
    • Quantisation error: difference between the stored value and the original value

    Microprocessor Applications

    • Most applications start with analogue data
    • Convert analogue data to digital domain using ADC (Analogue to Digital Converter)
    • Process data using a microprocessor
    • Convert digital data back to analogue using DAC (Digital to Analogue Converter)
    • Some applications might lack either an input or output but not both

    Transducers

    • Transducers convert signals from one form to another
    • Sound:
      • Microphone
      • Loudspeaker
      • Buzzer
      • Ultrasonic transducer
    • Vision:
      • LED
      • LDR (Light Dependent Resistor)
      • Photodiode
      • Camera sensor
    • Others:
      • Temperature
      • Pressure
      • CO2
      • Magnetometer

    Analogue-to-Digital Conversion (ADC)

    • In an N-bit ADC, the input voltage is divided into 2N levels
    • Resolution (R): the step between levels
      • R = VREF / 2N
    • Two main processes in an ADC:
      • Sample the input voltage
      • Quantise the sample into binary
      • Provide the digital sample to the CPU when asked
    • Dynamic range: DR = 6.02N + 1.76 dB

    Non-Uniform Quantisation

    • In non-uniform quantisation, the quantisation levels are not evenly spaced
    • Uniform quantisation is assumed in most cases

    Sampling

    • Sampling is defined by sample rate
    • Examples of sample rate:
      • Telephone speech: 8kHz
      • CD-quality music: 44.1kHz
      • Two-hourly measurement: 0.00014 Hz
    • Sample rate must be frequent enough to capture variations in the signal
    • Sampling too frequently wastes power, CPU cycles, and memory space

    Nyquist Theorem

    • States that a continuous signal can be perfectly reconstructed from its samples if the sample rate is at least twice the highest frequency component in the signal
    • Fs (Sample Rate) ≥ 2Fmax (Highest Frequency)

    Pulse Code Modulation (PCM)

    • Continuous sampling of a signal at rate Fs
    • Each sample is stored as a signed two's complement integer
    • Combines sampling and quantisation to represent analogue signals digitally

    Key Terms

    • ADC (Analogue to Digital Converter): Converts analogue data to digital data
    • DAC (Digital to Analogue Converter): Converts digital data to analogue data
    • Quantisation: Process of representing a continuous range of values using a finite set of discrete levels
    • Sample Rate: Number of samples taken per second
    • Nyquist Theorem: Theoretical minimum sample rate required to accurately reconstruct a signal

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    Related Documents

    Interfacing with an Analogue World PDF

    Description

    Explore the fundamental concepts of quantisation, microprocessor applications, and transducers in this quiz. Learn about how analogue data is converted to digital and the importance of quantisation in signal processing. Test your knowledge on the devices that aid in these conversions and their applications.

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