Piezoelectric Effect
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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
Internal working
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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.
Piezoelectricity
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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.
Artificial materials
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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
Configurations
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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
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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, microcircuit.
pressure sensors utilize
a diaphragm to collect
pressure, which is simply
force applied over an
area.
Signal Conditioning
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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.
Pressure Sensor
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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.
Pros and Cons
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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.
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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.
Typical ApplicationCombustion Monitoring
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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.
CPM--Features
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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.
CAPA System
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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/p’s,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.
P-V Diagram
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An example of a PV diagram display
on a Windows OS.
Corresponding TDC
diagrams can also
be obtained to
observe ignition
characteristics.
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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.
WINS PDD
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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.
Sensoria –WINS Network
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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.
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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
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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.
Hardware Features
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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