1 METR3100: Sensor Introduction http://www.mech.uq.edu.au/courses/metr3100/ Sensor Introduction Han Huang Room 45-212; Phone: 3365 3583 [email protected]METR3100: Sensors and Actuators METR3100: Sensor Introduction Introduction to sensors – What is a sensor? – What will we learn? – “Future” sensors: MEMS based sensors MEMS based sensors
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– What is a sensor?– What will we learn?– “Future” sensors:
MEMS based sensorsMEMS based sensors
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METR3100: Sensor Introduction
What is a sensor?
• Formal definition: “A device that receives and responds to a signal or stimulus”– American Heritage Dictionary of the English Language
• Informally, a sensor is a device that takes in information from the outside world. Based on the information, the sensor creates a signal on which a system can make a decision.
• A sensor, thus, has an input and an output
METR3100: Sensor Introduction
What is a sensor? (cont.)
• A sensor will measure some physical quantity and convert it into some electrical signal (e.g., voltage)
• You would also want to do something intelligent based on the signal (turn on a heater, sound an alarm, pass/fail an industrial part, etc)
What advantages do sensors have over using a humanWhat advantages do sensors have over using a human?
• Repeatability - sensor output is very stable over time whereas a human may suffer from fatigue
• Reliability - a sensor usually won’t need breaks, vacations…
• Harsh environments - a sensor can operate in many environments that humans may not
• Sensitivity - sensors can be more sensitive than the corresponding human sense
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METR3100: Sensor Introduction
Reliability Issue of Testing – A True Story
METR3100: Sensor Introduction
What will we learn?
Sensing systems– Temperature– Pressure– Strain– Force and torque– Displacement and transport– Vibration– Air pollution
Also including– Amplifiers and signal conditioning– Data acquisition and processing
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METR3100: Sensor Introduction
MEMS based sensorsMEMS based sensors
“Future” Sensors
METR3100: Sensor Introduction
What is a MEMS sensor?
• Microelectronic integrated circuits that have changed our lifestyle in the past two decades can be imagined as the "brains" of a system and MEMS augments this decision-making capability with "eyes“ and "arms", to allow the system to sense and control the environment.
• A sensor is described as “eyes” or “ears” or “nose”…
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METR3100: Sensor Introduction
What is MEMS
• MEMS refers to micro-electro-mechanical systems
• Tiny mechanical devices built onto semiconductor chips
• MEMS typically combine two or more properties on a single microchip, such as electrical, mechanical, biological, magnetic, optical or chemical properties
• Most MEMS generate or sense motions (like actuators, mirrors and cantilevers)
Toyota 32 x 32 (1K)-element piezoresistive pressure/tactile sensor array (Sugiyama et al. 1990).
Pressure Sensor
METR3100: Sensor Introduction
According to a report from Venture Development According to a report from Venture Development Corporation (Natick, MA), automotive market will Corporation (Natick, MA), automotive market will represent 5.2 percent of the overall $34.2 billion represent 5.2 percent of the overall $34.2 billion
MEMS market in 2006 or more than $1.7 billion, up MEMS market in 2006 or more than $1.7 billion, up from $1.1 billion in 2001.from $1.1 billion in 2001.
Conventional air bag pressure sensor device: Conventional air bag pressure sensor device: US$50US$50. . MEMS based pressure sensor and device: MEMS based pressure sensor and device: US$7US$7
The Impact
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METR3100: Sensor Introduction
Gyroscope• It took five years to develop gyroscopes
• Introduced on the market in 2000
• Now several millions are produced every year by Robert Bosch GmbH
METR3100: Sensor Introduction
Pressure sensor
• Sensor Orbital Research Inc. develops a MEMS-based high temperature pressure transducer technology for diesel and turbine engine applications. • Based on a thin film strain gage configuration using MEMS fabrication techniques and a highly sensitive, novel thin-film material . • The technologies combine synergistically resulting in a unique, high temperature sensor with high sensitivity at an affordable price . • Have high gage factor (sensitivity ) and high temperature capability is significantly greater than competing technologies. • Demonstrated in the harsh diesel engine environment (reliability )
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METR3100: Sensor Introduction
High Temperature Pressure Sensor
Orbital Research Inc.
Pressure Ranges: 0-60, 0-1000, 0-3000, psi Operating Temperature: 400 oC for Diesel Engines - Can be tailored for higher operating temperatures up to 600 oC.
Accuracy: 1% full scaleProof Pressure: 150% full scale Burst Pressure: 200% full scale Wheatstone Bridge Design Gage Factor: 35 to 100
Dynamic Frequency Response: >30 kHz Dimensions: < = 9 mm dia. Sensing element size: small as 0.5 x 0.5 mm
A 4th year mechatronic student is designing high pressure sensor for hypersonic application
METR3100: Sensor Introduction
Cricket-Inspired Sensory Hairs with Capacitive Motion Detection
Courtesy University of Twente, MESA+
Research Institute
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METR3100: Sensor Introduction
• Perception of air flow and escape action of crickets
• Mechanical and functional properties of filiform hair• Design and realize large arrays of MEMS sensors
METR3100: Sensor Introduction
• Si capacitive sensor: made of single crystal silico n and glass• Design ensures exceptional reliability• Excellent accuracy and stability over time and temp erature.
Capacitive detection principle is simple and stable, based on the variation of a gap between two planar surfaces. The capacitance or charge storage capacity of a pair of plates depends on the gap width and plate area.
Accelerometer
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METR3100: Sensor Introduction
Accelerometers in two basic types: comb and diaphragm.
With comb-type MEMS accelerometers , changes in g-forces cause the interleaved fingers of the comb to bend, resulting in a measurable change in conductivity, also called a piezoelectric effect.
Diaphragm type accelerometers have a thin silicon diaphragm over a charged plate. As the distance between the flexible silicon layer and the charged plate change, so does the capacitance.
Comb-type Accelerometer
METR3100: Sensor Introduction
The cantilever structure was formed out of silicon and was made suitably to comply with the mass or pressure variations due to change in humidity.
The design also incorporates integration of the platinum based temperature sensor and a platinum based heater.
The key point is to keep all the electrodes and leads at one convenient end for easy packaging and providing power to the sensor and to take leads for the outputs.
using a micro cantilever beam
K.Govardhan and Z.C.Alex, Proceedings of ISSS 2005
Humidity Sensor
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METR3100: Sensor Introduction
Inexpensive and easy-to-use three-axis accelerometer devices will find applications in toys, industrial production equipment, robotics and automotive systems. It is also useful as a general-purpose vibration sensor for industrial equipment and domestic appliances.
Three-Axis Linear Accelerometer, in a compact package, the first one-chip three-axis MEMS accelerometer sensor, plus an interface chip that translates movement and inclination into calibrated analog voltage or digital outputs. Compared to multiple one-axis sensors the new device simplifies assembly, reduces size and cuts production costs.
Accelerometers based on silicon-micromachined MEMS technology are effective because they provide high sensitivity and precision together with the economies of scale of the wafer batch process used to make integrated circuits.
Other Applications
METR3100: Sensor Introduction
Omron will display its innovative portfolio of photomicrosensors(optoswitches) and intelligent sensors for detection of mass and velocity gas flow, and differential and gauge pressure changes
Among the highlights of the show will be Omron's ne w range of MEMS precision velocity and large mass airflow sensors and the new capacitive touch sensor
Omron's D6F-W MEMS-based sensors are to detect clogged air intake filters and air velocity flows in office automation equipment, domestic air purifiers and coolers, and other more conventional applicatio ns.
Health Products
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METR3100: Sensor Introduction
Military Uses
METR3100: Sensor Introduction
High sensitivitywide bandwidth detection
Real time spectral detectionfast tunable filters
High spectral resolutionMEMS technology for Large 2D arrays