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