ELET 2143 Embedded Controller Fundamentals
1- Transducers
2- Measurement Systems
3- Analog-to-Digital Conversion
FALL 2007
1- Transducers
What is a transducer ?
Give two examples
A transducer is a sensing device that converts a
physical input into an electrical output, usually a
voltage.
• Thermocouple
• Strain Gage
• Infrared Sensor
What is an Infrared Signal ?
Infrared signal is an electromagnetic radiation of
a wavelength longer than that of visible light, but
shorter that of radio waves
A very small part of the electromagnetic spectrum
can be seen by the human eye, this is between the
wavelengths 380 and 750 nm.
This part of the electromagnetic spectrum is called
visible light.
Near IR: 750nm - 5 μm
Commercial Infrared Diodes and Detectors
Phototransistors (Photodiodes)
Phototransistors are high-sensitivity light receiving devices
The Sharp GP2D12 Infrared Object Detector
The Sharp GP2D12 Infrared Object Detector
2- Measurement System
3- Analog-to-Digital Converter
What is the Analog Full Scale Voltage (FSV) in an
ADC ?
What is the Resolution of an ADC ?
Resolution = FSV / 2n
n is the number of bits in the converter
Example:
Assume a 10 bit ADC has a minimum input voltage
of 0 V and a maximum input voltage of + 10V.
a) What is the resolution of this ADC ?
b) If the input voltage is 3 V, what digital value do
you expect in the output ?
Ans: a) res = 9.76 mV, b) (307)10 = 100110011
The ADC in the 68HC11
The ADC in the 68HC11