Piezoelectric Effect

1
Piezoelectric Effect

• Appearance of an electric potential across
  certain faces of a crystal when it is subjected
  to mechanical pressure
• The word originates from the greek word
  piezein, which means to press
• Discovered in 1880 by Pierre Curie in quartz
  crystals.
• Conversely, when an electric field is applied to
  one of the faces of the crystal it undergoes
  mechanical distortion.
• Examples --- Quartz, Barium titanate, tourmaline

2
Internal working

• The effect is explained by the displacement of
  ions in crystals that have a nonsymmetrical unit
  cell
• When the crystal is compressed, the ions in each
  unit cell are displaced, causing the electric
  polarization of the unit cell.
• Because of the regularity of crystalline
  structure, these effects accumulate, causing the
  appearance of an electric potential difference
  between certain faces of the crystal.
• When an external electric field is applied to the
  crystal, the ions in each unit cell are
  displaced by electrostatic forces, resulting in
  the mechanical deformation of the whole crystal.

3
Piezoelectricity

• displacement of electrical charge due to the
  deflection of the lattice in a naturally
  piezoelectric quartz crystal
• The larger circles represent silicon atoms, while
  the smaller ones represent oxygen.
• Quartz crystals is one of the most stable
  piezoelectric materials.

4
Artificial materials

• polycrystalline, piezoceramics are man made
  materials which are forced to become
  piezoelectric by applying large electric field.
• high charge sensitivity
• materials available which operate at 1000 F (540
  C)
• characteristics vary with temperature

5
Configurations

• Red indicates the crystal
• Arrows indicate the direction of applied force
• the compression design features high
  rigidity, making it useful for implementation in
  high frequency pressure and force sensors

6

• Grey- test structure.
• Red- piezoelectric crystals
• Blue- Sensor housing
• The black electrode is where the charge from the
  crystals accumulates before it is conditioned by
  the yellow, micro-circuit.
• pressure sensors utilize a diaphragm to collect
  pressure, which is simply force applied over an
  area.

7
Signal Conditioning

• Signals from the sensors can be processed by the
  micro-electric circuit either internally or
  externally.
• Conditioning involves the conversion of the
  signal to a low impedance voltage, amplification
  and filtering.

8
Pressure Sensor

• A typical Quartz crystal sensor with inbuilt
  micro-electric circuitry and a diaphragm.
• These sensors measure dynamic pressures, and are
  not generally used for static pressure sensing.
• Proper and accurate alignment of the sensor is
  very important for higher sensitivity.
• Sensors used in high temperature conditions(e.g.
  combustion chamber of an engine) use either
  recess mounting, baffled diaphragm or thermal
  protection coatings to reduce negative signal
  effects.

9
Pros and Cons

• Have a high Stiffness value and produce a high
  output with very little strain.
• Ideal for rugged use.
• Excellent linearity over a wide amplitude.
• Ideal for continuous online condition monitoring
  smart systems.

• Can be used only for dynamic pressure sensing as
  in case of static sensing the signals will decay
  away.
• Operation over long cables may affect frequency
  response and introduce noise and distortion, the
  cables need to be protected.

10
Typical Application-Combustion Monitoring

• Pressures developed during the combustion process
  is continuously measured by sensors mounted on
  the cylinder heads.
• Continuous Pressure monitor(CPM) systems are the
  basic data acquisition and data reduction
  software and hardware units.

11
CPM--Features

• Continuous updating of Peak Pressure, Location of
  Peak, and Standard deviation of Peak Pressure
• Continuous calculations of combustion quality and
  engine balance.
• Serial communications with SCADA(Supervisory
  Control and Data Acquisition systems.
• Running trends of displayed values.

12
CAPA System

• Uses a PMI Pressure analyzer(Piezoelectric) to
  display real time parameters of the engine using
  P-V displays.
• The pressure is calculated from the sensor
  outputs and the volume is obtained from an
  advanced crank angle encoder which gives the
  crank positions from which the displaced volume
  is calculated.
• Expert systems send signals to actuate other
  controllers (electronic governors, fuel
  p/ps,exhaust v/v actuators, lubricators etc) for
  optimal performance on a real time basis.
• Each controller unit has the processing power to
  process the signals and accordingly produce
  output for the individual actuator to change
  various parameter settings continuously.

13
P-V Diagram

• An example of a P-V diagram display on a Windows
  OS.
• Corresponding TDC diagrams can also be obtained
  to observe ignition characteristics.

14

• Peak pressure indicator display at TDC,provides
  ignition characteristics.
• Display for a 4 unit engine. The signal outputs
  from these sensors are transmitted to other
  controllers to actuate and adjust critical
  parameter settings in order to achieve efficient
  combustion.

15
WINS PDD

• WINS PDD (Wireless Integrated Network Systems
  Prognostic Data Delivery System) is an end-to-end
  network solution enabling continuous vehicle
  diagnostic monitoring based on Sensoria
  Corporation's WINS technology.
• The WINS PDD solution provides an unprecedented
  level of access to vehicles for analysis of
  vehicle performance, reliability, and maintenance
  status.

16
Sensoria WINS Network

• Consists of Network Routers, Internet Access
  points and E comm products
• Wireless Integrated Network Systems(WINS)
• enables networks to provide connectivity to
  and within the automobile, the home, and monitor
  equipment and processes.

17

• Network Routers are real-time processors embedded
  in vehicles and assets that create a secure
  network bridge between multiple embedded networks
  and Wide Area Networks, including the Internet.
• Internet Access Points are real-time data routers
  and communication servers that interface embedded
  Network Routers to the Internet or an Enterprise
  Network via a Sensoria 2.4GHz local area RF
  Modem.
• The e-Service Products include the WINS Server,
  based on Windows NT, WINS Database, based on
  Microsoft SQL Server. The WINS Server is
  responsible for managing the entire network and
  providing Internet access to the WINS Database

18

• IDB-C is the first of a family of in-vehicle
  networks, and is expected to be deployed in some
  model year 2002 vehicles. IDB-C compliant devices
  will soon enter the market.
• The IDB-C Reference Platform provides the
  hardware interface between the various media
  being integrated.
• The Sensoria IDB-C Reference Platform is the
  AMI-C (Automobile Multimedia Interface
  collaboration) reference platform used to develop
  the IDB-C reference drivers available as part of
  the AMI-C specification.

19
Hardware Features

• Infineon C164CI 16 bit Processor
• 20 MHz clock rate
• 256kB SRAM
• 256kB Flash ROM
• CAN 2.0B controller
• 250 kbps raw data rate
• RS-232 Interface
• 115.2 kbps UART
• DB-9 serial interface
• 3 channel LISA interface
• Left, Right, and microphone channels
• Optional pre-amp for microphone