Download ENGI 1040 - Memorial University of Newfoundland

Basics of Analog to Digital
Converter
ENGI 1040
Mechatronics Module
Sensors
• A device that measures or detects a realworld condition, such as motion, heat or
light and converts the condition into an
analog electrical voltage or signal can be
called sensor.
• Example : An optical sensor detects the
intensity or brightness of light and shows it
in terms of electrical voltage/ signal.
Analog Signal
• An Analog or analogue signal is
any continuous electrical signal that
increases and decreases in response to
changes in sound, light, heat, position, or
pressure.
• It is called analog as it is analogues to the
change of the measuring domain (light,
distance etc.)
Analog Signal
Signal (Voltage)
Maximum
Say 7 Volt
Minimum
0 Volt
Time
Say, a voltage response ANALOGUES to light intensity
Digital Signal
• A digital signal is the representation of
analog electrical signal by some discrete
digital values.
Digital Signal
ADC Output
Maximum
say, 111
Digital
Value
(eg. 011)
Minimum
t1 t2 t3
000
Time
Minimum
0 Volt
7
111
6
110
5
101
4
100
3
011
2
010
1
001
0
000
Digital Output 
Maximum
(Full Scale)
Say 7 Volt
Levels formed
by 3 bit A/D 
Example : 3 bit A/D
Time
Minimum
0 Volt
7
111
6
110
5
101
4
100
3
011
2
010
1
001
0
000
Digital Output 
Maximum
(Full Scale)
Say 7 Volt
Levels formed
by 3 bit A/D
3 bit A/D
Time
Resolution of A/D converter
• Resolution of an ADC or A/D converter is
defined by bits.
• Say, 3 bit A/D converter
– It is going to divide the full scale of input
analog signal into 23-1 = 7 segments or levels
• The more the resolution the higher the
precision of signal conversion.
4 bit A/D
Maximum
(Full Scale)
Say 7 Volt
15 1111
1110
…
…
…
…
…
0001
0000
Digital Output 
0
Levels formed
by 4 bit A/D 
Minimum
0 Volt
Time
Application
• Analog-to-Digital converters
or A/D
converters - are widely used by many
engineers and scientists of all types, often
without their realizing it.
• Whenever we make a measurement of a
real world responses, and that response is
taken into a computer, an A/D is used.
• Example: measuring distance, light
intensity, rotation of any device (RPM) etc.
Optical Sensor in 1040 Lab
Voltage output
Analog Signal
produced by the
sensor
obstacle
emitting
Distance from an obstacle
(cm)
receiving
Optical Sensor in 1040 Lab
Obstacle
Lens
LED
Position
Sensitive
Detector
Optical Sensor in 1040 Lab
Obstacle
Lens
LED
Position
Sensitive
Detector
Position Sensitive Detector
Application of an A/D by studying a
case
Next Week….