Sensor Data Collection
September 11, 2008
Sung-Bae Cho
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Agenda
• What is Sensor?
• Sensors in Ubiquitous Environment
• Experimental Sensor Kits
• Appendix: Acceleration Sensors
What is Sensor?
• Sensor
– A device that measures a physical quantity and converts it into a signal
which can be read by an observer or by an instrument
• Sensor sensitivity
– How much the sensor's output changes when the measured quantity
changes
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Sensor Types
• Thermal:
– Temperature/heat sensors
• Electromagnetic:
– Electrical resistance/voltage/power sensors, magnetism sensors, metal
detectors, RADAR
• Mechanical:
– Acceleration, position, pressure, switch, liquid sensors
• Chemical:
– Odor (smell) sensor, oxygen sensors
• Optical radiation:
– Light sensors, infra-red sensor, proximity sensor
• Acoustic: Sound sensors
• Motion sensors:
– Radar gun, speedometer, tachometer, odometer
• Orientation sensors: Gyroscope
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Features of Sensor (1)
• Light Sensors
– Detecting light intensity, density, reflection, color temperature, type of light
– Rich information, very low cost
• C-MOS Camera
– Visual information about the environment
– Processing power and storage needs are often large
– Users feel uncomfortable
• Location sensor
– GPS(Global Positioning System) is mostly used
– Coarse location information
• Cellular network infrastructures: Global System for Mobile
Communications (GSM)
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Features of Sensor (2)
• Audio, Microphones
– Interesting information: Noise level, type of input, base frequency
– Using minimal processing: Less than 200 bytes of RAM
– Multiple microphones: Richer information
– Very cheap
– Can be extended up to speech recognition by using more processing
power
– Ultrasonic sensors: Augment human sensory capabilities
• Accelerometers
– Information on the inclination, motion, acceleration of the device
– Typical: Mercury switches, angular sensors, accelerometers
– Especially interesting in examination of usage patterns
• Touch sensor
– Can reduce energy consumption: operative in the user's hand
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Features of Sensor (3)
• Air pressure
– Some hints: Closing door
• Temperature sensor
– Most sensors are cheap and easy to use
– Detect body heat, arctic or desert environments
• Passive IR sensors (Motion detector)
– Movement of the device itself is detected as well
• Proximity sensors
– Determine a proximate distance between a physical object in the range
and the device
• Gas sensor
– Problem: delay in measurement, enormous energy consumption
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Features of Sensor (4)
• Biosensors
– User awareness
– Skin resistance, blood pressure: sports and medical applications
– Emotional state of the user may be obtained
• Magnetic field
– Similar to a compass
– Direction of a device or movement can be determined
– This sensor can give false information
• Tilt sensors
– Determine the tilt angles of the device
• No-power sensors
– Metal ball switches, mercury switches, solar panels
– Extremely low power consumption
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Agenda
• What is Sensor?
• Sensors in Ubiquitous Environment
• Experimental Sensor Kits
• Appendix: Acceleration Sensors
Sensing Environments
• Information processing has been thoroughly integrated into everyday objects
and activities  Ubiquitous environments
• Paradigm change
– Ordinary: a single user consciously engages a single device for a
specialized purpose
– New: engages many computational devices and systems simultaneously,
in the course of ordinary activities, and may not necessarily even be
aware that they are doing so
• Related technologies
– Ubiquitous computing, pervasive computing, ambient intelligence
– Haptic computing, things that think
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Sensors in Ubiquitous Environments
• Body Sensor
– Physiological sensor
– Biosensor: Identity, emotion, facial expression, behavior, gait
– Location sensor (GPS)
• Environment Sensor
– Video camera
– Light
– Noise & sound
– Temperature & humidity
– Pressure
– Movement
– Acceleration
• Object Sensor
– Position & status of object
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Service & Applications
• Application model
• Services
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Sensor Data & Processing
(ETRI’06)
Input Data
Sensor
Video
CCD
CMOS
Audio
Microphone
Position
GPS
RF (Radio Frequency)
system
Bio
ECG, EEG, EMG, PPG,
GSR
Skin temperature
Respiration
Blood Pressure (BP)
Environment
Movement
Data Processing Techniques
•Compression: MPEGX, H.26X, JPEG
•Facial detection techniques
•Data streamining techniques
•Compression: MPEGX, G.7XX, AAC
•Audio data processing techniques
•Voice recognition
•Position detection
•Map data mapping (addressing)
•Time detection
• Data mining
techniques
•Heart Rate Extraction
• Data
•Stress Level
searching
•Emotion Estimation
techniques
•Alpha Wave Detection
•Electrohystereogram, body temperature • Feature
extraction
extraction
techniques
•Health Monitoring
•Noninvasive BP estimation
Light, Humidity,
•Noise reduction
Temperature, Ultraviolet
•Awareness Environment
sensor
•Falling detection
•Gesture recognition (walking,
running, ...)
•Human interface
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Development of Sensor Kit
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Object Sensors
LoveGety
Intelligent object of Swiss ETH
Smart Bag - MIT bYOB
Project
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Body Sensors (1)
Microsoft’s SenseCam
Microsoft’s Spot Watch
Body Media’s ArmBand
Adias’ Intelligent Shoes
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Body Sensors (2)
Olympus Optical Co., Ltd. is pleased to announce its new
wearable user interface technologies.
Employing gestures and other hand movements for input, the system
is an ideal match for new wearable PCs.
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Body Sensors (3)
eSleeve of Univ. of Bristol, UK
http://www.redwoodhouse.com/wearable/index.html
http://wearables.cs.bris.ac.uk/public/wearables/esleeve.htm
http://www.ices.cmu.edu/design/streetware/
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Environment Sensors
Smart Dust of UC Berkeley
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Integrated Sensors (1)
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Integrated Sensors (2)
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Integrated Sensors (3)
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Smart Car (GM/CMU)
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Sensor Model for Smart Car
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Sensor Data from Mobile Phone
Battery log
MP3 Player log
GPS log
SMS log
PicView Log
Photo log
Call log
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Mobile Log Data
Log
GPS
Call
SMS
Photographing
Weather
MP3 Player
Charging
Information
latitude, longitude, velocity, direction, date, time
caller's phone number, call/receive/absence log, time span,
start/end time
sender's phone number, call/receive/absence log, time
span, start/end time
photo file name, taking time
weather, visibility range (km), cloud degree (%),
temperature (°C), discomfort index, effective temperature
(°C), rainfall (mm), snowfall (cm), humidity (%), wind
direction, wind velocity (m/s), barometer (hPa)
title, time span, start/end time
charging status, time span, start/end time
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Agenda
• What is Sensor?
• Sensors in Ubiquitous Environment
• Experimental Sensor Kits
• Appendix: Acceleration Sensors
Experimental Sensor Kits
• Introduction of famous experimental sensor kits
• LabPro
– An environmental sensor kit
– Vernier Software's data collection device
– Collects data from a wide variety of sensors
– Can be used with a computer, a TI graphing calculator,
Palm handheld, or on its own as a remote data collector
• ArmBand
– A body sensor kit
– Body Media's data collection device
– Collects physiological data that would provide an insight for recognizing
human activity and condition
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LabPro
• Vernier LabPro Interface
• Sensor
– Stainless Steel Temperature Probe
– Light Sensor
– Microphone
– Relative Humidity Sensor
• Logger Pro 3.1 Application
• LabPro Visual C++ SDK
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LabPro
Vernier LabPro Interface
• Main body for data collection
– Having flexibility and mobility
• Data collection
– Supporting 50,000Hz sampling
– Can store 12,000 data in memory
• Companion devices
– PC
• Linked by serial or USB cable
• Real-time interaction
– TI Graphic Calculator
• Running with LabPro
– Palm, Sony PDA
– Stand-Alone Data Logger
• 6 channels for data collection
– 4 analog channel: supporting 40 kinds of sensors
• temperature, oxygen determination, air pressure, pH, …
– 2 digital channel: ultra-sonic sensor, pho, …
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Stainless Steel Temperature Probe
• Used in organic liquids, salt solutions, acids, and bases
• Measurement scope
– -40 ~ 135 °C (-40 ~ 275 °F)
– Heat resistance limit : 150 °C
• Accuracy
– ±0.2 °C at 0 °C
– ±0.5 °C at 100 °C
• Reaction time
– 95% in 11 sec
– 98% in 18 sec
– 100% in 30 sec
• Probe length: 15.5 cm
• Stainless steel body: length (10.5 cm), radius (4.0 mm)
• Probe handle: length (5.0 cm), radius (1.25 cm)
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LabPro
LabPro
Light Sensor
• Can be used for measurements of light intensity in a variety of situations
– Perform inverse square light intensity experiments using a point source of
light.
– Conduct polarized filter studies
– Demonstrate the flicker of fluorescent lamps and other lamps
– Carry out solar energy studies Switch for resolution change
– Perform reflectivity studies
• Resolution
– Low: 0 ~ 600 lux
– Medium: 0 ~ 6000 lux.
– High: 0 ~ 150,000 lux.
Light Sensor
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LabPro
Microphone
• Can be used for a variety of activities with sound waves:
– Demonstrate how the wave pattern changes when frequency and
amplitude are changed
– Compare the waveforms from various musical instruments
– Capture the waveform of the sound of a tuning fork and model the sine
wave using a function
– Measure the speed of sound
by using reflected sound waves in a tube
– Demonstrate beat patterns
– Display the fast Fourier transform (FFT) of a sound
• Resolution
– 20 Hz ~ 16,000 Hz
• Maximum frequency for LabPro: 5,000Hz
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LabPro
Relative Humidity Sensor
• Measure relative humidity in the air as part of a weather station:
– Monitor indoor humidity for health reasons
– Optimize conditions in a greenhouse or terrarium
– Determine when static electrical discharges will be a problem
– Study transpiration rates of plants by monitoring relative humidity in
sealed jars containing plants
• Range: 0 ~ 95%(± 5%)
• Response Time: (time for a 90% change in reading):
– In still air: 60 min
– With vigorous air movement: 40 sec
• Resolution
– 12-bit with LabPro: 0.04% RH
• Total Accuracy
– With Saturated salt calibration: ±2% RH
– With standard calibration: ±10% RH
• Operating Temperature Range: 0 ~ 85°C
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LabPro
Logger Pro 3.1 (Data & Graph)
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ArmBand
• Famous wearable sensor of SenseWear
• Collection data
– heat flux, accelerometer, galvanic skin response,
skin temperature, near body temperature
• Store about 5 days of data
Source: http://www.armband.it/
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ArmBand
ArmBand Log Data
• 참고: Professional License Key 필요
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ArmBand
ArmBand - Generated Report
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Agenda
• What is Sensor?
• Sensors in Ubiquitous Environment
• Experimental Sensor Kits
• Appendix: Acceleration Sensors
Accelerometer
• Measurement of static gravitational force
– e.g. Tilt and inclination
• Measurement of dynamic acceleration
– e.g. Vibration and shock measurement
• Inertial measurement of velocity and position
– Acceleration single integrated for velocity
– Acceleration double integrated for position
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Accelerometers’ Principle
• Acceleration can be measured using a simple mass/spring system.
– Force = Mass * Acceleration
– Force = Displacement * Spring Constant
– So Displacement = Mass * Acceleration / Spring Constant
Change in Displacement
Add Acceleration
MASS
MASS
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MEM’s Accelerometers
• We use Silicon to make the spring and mass, and add fingers to make a
variable differential capacitor
• We measure change in displacement by measuring change in differential
capacitance
SPRING
APPLIED
ACCELERATION
MASS
FIXED
OUTER
PLATES
SENSOR AT REST
ANCHOR TO
SUBSTRATE
CS1 < CS2
RESPONDING TO AN APPLIED ACCELERATION
(MOVEMENT SHOWN IS GREATLY EXAGGERATED)
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MEM’s Accelerometer Example
Source: Great MEMS education site
www.ett.bme.hu/memsedu/
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Gyroscope
• A device that can measure angular motion or displacement
– An instrument to maintain a specific direction
– Mostly used in airplanes, and spacecrafts
• Key Phenomena:
– Precession: The gravity defying part of Gyroscope
• Gyro is spinning on its axis (1)
• A force is applied to rotate its spin axis (2)
• Gyro is reacting to the input force along an axis perpendicular to the input
force (3)
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Gyroscope Principles
• Principle of operation
– The simplest gyroscopes use a high speed, rotating inertial disk that is
loosely coupled to the frame holding it.
– A rotation in the frame imparts a torque (rotation) on the spinning disk,
which processes (rotates) as a result (conservation of angular
momentum).
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Principle of operation
• Practical uses usually limit the movement to measure only one axis of rotation
(roll, pitch or yaw).
• The induced torque is monitored by a meter which counteracts the torque
with springs or a similar restoring force.
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MEMS Gyroscope Principles
• Coriolis effect
– Motion in a rotating reference frame leads to “sideways” movement
– Can’t walk a straight line in a rotating reference (merry-go-round)
without exerting a sideways force (or acceleration).
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Gyroscope - Coriolis Effect
• This effect shows up on earth since we are in a rotating reference frame.
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Measuring Coriolis Effect
• Constrained motion means a force is imparted.
• By measuring the imparted force (or its effect on an oscillator), we can
measure the angular velocity. Almost all MEMS gyroscopes use this feature.
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Tuning Fork Gyroscope
• A tuning fork is simple example of the Coriolis effect and how it can be used
to monitor angular motion.
• By measuring the amplitude of oscillation in the sideways direction, the
angular motion can be deduced. Used in Daimler Benz AG MEMS gyroscope.
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Vibrating Ring Gyroscope
• A ring is flexured back and forth in resonant mode. The Coriolis effect induces
flexure that is sideways (and out of phase) with the driving flexure.
• Since the Coriolis force vibrates the ring sideways, it produces a second
mode of vibration which adds to the first. The result is a “rotation” of the mode
pattern of the ring. Most MEMS gyros use this method in closed-loop mode.
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Gyro-based Sensors
• Gyro-Compass:
– Gyroscopes mounted in a set of gimbals
– As the gyro spins, it maintains its direction
• Inertial Navigation System (INS):
– Gyro-Compass + 3 Accelerometers
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Applications
• Aerospace:
– Inertial guidance systems
• Automotive:
– Angular rate sensors (for traction control, etc.)
• Entertainment/consumer:
– Virtual reality sensors, pointing devices, etc.
• Industrial automation:
– Motion control, robotics
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Gyroscope Application Example
• Applications on the horizon: Human motion sensing VR, Human/Machine
interface
– Consumer and game markets require lower performance specs and lower
costs.
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Gyroscope Application Example: Segway
• Silicon Sensing Systems VSG ring sensor “Dynamic Stabilization”
• Five sensors used to monitor orientation of the scooter, sampled at 100
times/second. Sensors include VSG ring gyroscopes and liquid-filled tilt
sensors
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