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
Kin 304 Fall 2013

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
Kin 304 Fall 2013

6. Binary - Base of 2 41
Kin 304 Fall 2013

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 Encoding
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
Encoding
Assigning a digital code
A to D

15. 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

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

17. Resolution Calculation
12 bit converter, -10v to +10v
-10v to +10v = 20 v
12 bit resolution = 4096 possible values
20v / 4096 = v per bit (4.88 mv per bit)
A to D

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