Instrumentation Ali Karimpour Associate Professor Ferdowsi University of

Instrumentation Ali Karimpour Associate Professor Ferdowsi University of Mashhad

An Introduction to Piezoelectric Transducers By Hasan Saravy

Piezoelectric Effect v The ability of some materials Mechanical stress Electrical potential How? 3

Physics of Piezoelectricity Asymmetries in the crystallographic structure Applied force Polarization (separate charges) Potential diff. 4

Definition of Piezoelectricity Null polarization Polarization in the same direction as the stress Perpendicular polarization 5

Materials that exhibit piezoelectric effect v Synthetic crystals: u u v Langasite (La 3 Ga 5 Si. O 14) Gallium orthophosphate (Ga. PO 4) Synthetic ceramics: u u Barium titanate (Ba. Ti. O 3) Sodium tungstate (Na 2 WO 3) v Polymers: u v v Polyvinylidene fluoride (PVDF) Some of semiconductors Natural materials: u u Quartz Sucrose Wood, silk, etc. In body: • Bone, Tendon, DNA, etc. 6

Piezoelectric Sensors v A piezoelectric sensor measures changes in pressure, acceleration, strain, or force by converting them to an electrical charge. v For the measurement of various processes (dynamic events). v Piezoelectric sensors act as a high-pass filter. 7

Piezoelectric Sensors v Frequency response of a piezoelectric sensor; output voltage vs applied force Why? 8

Applications v The most common physical quantities can be measured are pressure, strain and force. 9

Applications v For measuring acceleration (lead to measuring vibration in pumps, motors, etc. ) F 10

Applications v Ultrasonic transducers u u u Based on piezoelectric material For converting ultrasound waves (sound pressure) to electrical signals and vice versa In different frequency depend upon the applications 11

Applications v Ultrasonic transducers u Measuring distance Fluid Level 12

Applications v Ultrasonic transducers u Object Detection (for smart parking) 13

PCB Piezotronics Inc. v For 30 years, PCB Piezotronics has been manufacturing piezoelectric sensors for dynamic pressure, force, vibration, and shock, measurements. 14

For example (Model 102 B 03) v Dynamic pressure quarts sensor v Suited for high-temperature shock and blast measurements and for other applications requiring very high frequency, near non-resonant response. 15

For example (Model 102 B 03) 16

For example (Model 102 B 03) 17

Why do we use piezo sensors? v v Small size Light weight 2 -wire operation Wide temperature range v v v Ultra low noise Simple signal conditioning Broad frequency range Stability Linearity 18

Drawback v Cannot be used for truly static measurements. u In conventional readout electronics, imperfect insulating materials and reduction in internal sensor resistance causes a constant loss of electrons and yields a decreasing signal. 19