23-07-2012, 02:19 PM
Introduction to Sensors
[attachment=28504]
Sensors?
American National Standards Institute
A device which provides a usable output in response to a specified measurand
A sensor acquires a physical quantity and converts it into a signal suitable for processing (e.g. optical, electrical, mechanical)
Nowadays common sensors convert measurement of physical phenomena into an electrical signal
Active element of a sensor is called a transducer
Transducer?
A device which converts one form of energy to another
When input is a physical quantity and output electrical → Sensor
When input is electrical and output a physical quantity → Actuator
Commonly Detectable Phenomena
Biological
Chemical
Electric
Electromagnetic
Heat/Temperature
Magnetic
Mechanical motion (displacement, velocity, acceleration, etc.)
Optical
Radioactivity
Common Conversion Methods
Physical
thermo-electric, thermo-elastic, thermo-magnetic, thermo-optic
photo-electric, photo-elastic, photo-magnetic,
electro-elastic, electro-magnetic
magneto-electric
Chemical
chemical transport, physical transformation, electro-chemical
Biological
biological transformation, physical transformation
Need for Sensors
Sensors are pervasive. They are embedded in our bodies, automobiles, airplanes, cellular telephones, radios, chemical plants, industrial plants and countless other applications.
Without the use of sensors, there would be no automation !!
Imagine having to manually fill Poland Spring bottles
Accelerometer–II
Electromechanical device to measure acceleration forces
Static forces like gravity pulling at an object lying at a table
Dynamic forces caused by motion or vibration
How they work
Seismic mass accelerometer: a seismic mass is connected to the object undergoing acceleration through a spring and a damper;
Piezoelectric accelerometers: a microscopic crystal structure is mounted on a mass undergoing acceleration; the piezo crystal is stressed by acceleration forces thus producing a voltage
Capacitive accelerometer: consists of two microstructures (micromachined features) forming a capacitor; acceleration forces move one of the structure causing a capacitance changes.
Piezoresistive accelerometer: consists of a beam or micromachined feature whose resistance changes with acceleration
Thermal accelerometer: tracks location of a heated mass during acceleration by temperature sensing
Accelerometer Applications
Automotive: monitor vehicle tilt, roll, skid, impact, vibration, etc., to deploy safety devices (stability control, anti-lock breaking system, airbags, etc.) and to ensure comfortable ride (active suspension)
Aerospace: inertial navigation, smart munitions, unmanned vehicles
Sports/Gaming: monitor athlete performance and injury, joystick, tilt
Personal electronics: cell phones, digital devices
Security: motion and vibration detection
Industrial: machinery health monitoring
Robotics: self-balancing
Light Sensor
Light sensors are used in cameras, infrared detectors, and ambient lighting applications
Sensor is composed of photoconductor such as a photoresistor, photodiode, or phototransistor
Ultrasonic Sensor
Ultrasonic sensors are used for position measurements
Sound waves emitted are in the range of 2-13 MHz
Sound Navigation And Ranging (SONAR)
Radio Dection And Ranging (RADAR) – ELECTROMAGNETIC WAVES !!
[attachment=28504]
Sensors?
American National Standards Institute
A device which provides a usable output in response to a specified measurand
A sensor acquires a physical quantity and converts it into a signal suitable for processing (e.g. optical, electrical, mechanical)
Nowadays common sensors convert measurement of physical phenomena into an electrical signal
Active element of a sensor is called a transducer
Transducer?
A device which converts one form of energy to another
When input is a physical quantity and output electrical → Sensor
When input is electrical and output a physical quantity → Actuator
Commonly Detectable Phenomena
Biological
Chemical
Electric
Electromagnetic
Heat/Temperature
Magnetic
Mechanical motion (displacement, velocity, acceleration, etc.)
Optical
Radioactivity
Common Conversion Methods
Physical
thermo-electric, thermo-elastic, thermo-magnetic, thermo-optic
photo-electric, photo-elastic, photo-magnetic,
electro-elastic, electro-magnetic
magneto-electric
Chemical
chemical transport, physical transformation, electro-chemical
Biological
biological transformation, physical transformation
Need for Sensors
Sensors are pervasive. They are embedded in our bodies, automobiles, airplanes, cellular telephones, radios, chemical plants, industrial plants and countless other applications.
Without the use of sensors, there would be no automation !!
Imagine having to manually fill Poland Spring bottles
Accelerometer–II
Electromechanical device to measure acceleration forces
Static forces like gravity pulling at an object lying at a table
Dynamic forces caused by motion or vibration
How they work
Seismic mass accelerometer: a seismic mass is connected to the object undergoing acceleration through a spring and a damper;
Piezoelectric accelerometers: a microscopic crystal structure is mounted on a mass undergoing acceleration; the piezo crystal is stressed by acceleration forces thus producing a voltage
Capacitive accelerometer: consists of two microstructures (micromachined features) forming a capacitor; acceleration forces move one of the structure causing a capacitance changes.
Piezoresistive accelerometer: consists of a beam or micromachined feature whose resistance changes with acceleration
Thermal accelerometer: tracks location of a heated mass during acceleration by temperature sensing
Accelerometer Applications
Automotive: monitor vehicle tilt, roll, skid, impact, vibration, etc., to deploy safety devices (stability control, anti-lock breaking system, airbags, etc.) and to ensure comfortable ride (active suspension)
Aerospace: inertial navigation, smart munitions, unmanned vehicles
Sports/Gaming: monitor athlete performance and injury, joystick, tilt
Personal electronics: cell phones, digital devices
Security: motion and vibration detection
Industrial: machinery health monitoring
Robotics: self-balancing
Light Sensor
Light sensors are used in cameras, infrared detectors, and ambient lighting applications
Sensor is composed of photoconductor such as a photoresistor, photodiode, or phototransistor
Ultrasonic Sensor
Ultrasonic sensors are used for position measurements
Sound waves emitted are in the range of 2-13 MHz
Sound Navigation And Ranging (SONAR)
Radio Dection And Ranging (RADAR) – ELECTROMAGNETIC WAVES !!