Showing papers on "Piezoelectric sensor published in 1984"

Composite piezoelectric sensors

Abstract: A hydrophone is an underwater microphone or transducer used to detect underwater sound. The sensitivity of a hydrophone is determined by the voltage that is produced by a hydrostatic pressure wave. The hydrostatic voltage coefficient, gh, relates the electric field appearing across a transducer to the applied hydrostatic stress, and is therefore a useful parameter for evaluating piezoelectric materials for use in hydrophones. Another piezoelectric coefficient frequently used is the hydrostatic strain coefficient, dh, which describes the polarization resulting from a change in hydrostatic stress. The gh coefficient is related to the dh coefficient by the relative permittivity (K): gh = dh/ɛoK, where ɛo is the permittivity of free space.

Composite ultrasonic transducers and methods for making same

Abstract: A ultrasonic transducer using such a piezoelectric composite that a number of piezoelectric poles made of piezoelectric ceramics are arranged in a plate-like polymer matrix perpendicular to the plate surface. The volume ratio of the piezoelectric poles is set in a range of 0.15-0.75 and a spacing between every adjacent piezoelectric poles is set smaller than the thickness of the polymer plate, thereby resulting in a transducer which has higher sensitivity than the conventional one using a homogeneous piezoelectric ceramic plate.

Piezoelectric force/pressure sensor

Abstract: A piezoelectric force/pressure sensor capable of detecting the magnitude of static and dynamic force or pressure applied thereto, utilizes first and second transducers each having a piezoelectric member with opposed first and second surfaces; an electrode fabricated upon each of the first and second surfaces of each of the first and second piezoelectric members; and a member fabricated of a material of known resiliency having first and second opposed surfaces each attached to one of the electrode-bearing first and second surfaces of a different one of the piezoelectric transducers. A first of the piezoelectric transducers is excited to vibrate in the thickness mode. The vibrations are coupled through the interposed elastic middle layer and are transformed to provide an electrical output from the sensor which is responsive to the force/pressure applied along the axis of the transducer-resilient member-transducer sandwich.

Flexible Composite Piezoelectric Sensors

Abstract: The piezoelectric properties of several different composites with 0-3 connectivity are reviewed. In these composites a piezoelectric ceramic powder such as PbZr1-,Tix03 (PZT), PbTi03 or Pbl-xBixTil-TFex03 is used as a filler in a polymer matrix. The values of hydrostatic voltage coefficient ih of these composites are higher than the corresponding properties of single phase materials. Composites with PbTi03 or (Pb.Bi)(Ti.Fe)03 as fillers have higher piezoelectric voltage coefficients than PZTpolymer composites because of the greater anisotropy and lower dielectric constants of these systems. By adding a small amount of carbon to the piezoelectric composite, poling can be carried out at much lower voltages and shorter poling times, making it possible to mass produce the composites. Fabrication of 0-3 composites is a

Method for forming a pressure sensor

Abstract: A pressure sensor comprising a piezoelectric material formed in a geometry which provides a piezoelectric output signal when subjected to a pressure. The piezoelectric material also has a pyroelectric output signal. The present sensor further comprises conductive contacts having a geometry for enhancing the piezoelectric output signal and for substantially eliminating the pyroelectric output signal.

Method and apparatus for setting and changing parameters or functions of an implanted device

Abstract: A piezoelectric device and method are provided for setting or adjusting parameters or functions of an implanted device, such as the pacing rate of a pacer, at the will of its user/wearer or others, simply by making slight impacts on the user/wearer's body near the implanted piezoelectric device. The device has a piezoelectric sensor which picks up the physical impact and converts it to an electrical signal. Additional amplification and detection/decoding circuits can be provided to strengthen the signal and to separate intentional impacts from any unintentional impacts and noise.

Bending type piezoelectric actuator

Abstract: PURPOSE:To contrive the improvement in reliability by reduction in shearing strain between piezoelectric elements and in breakdown of an adhesive layer by a method wherein the titled device is so constructed that a voltage nearly proportional to the distance from the center of thickness of the main body of piezoelectric actuator to the center of thickness of each piezoelectric element may be impressed on each piezoelectric element. CONSTITUTION:The main body of bending type actuator is constructed by adhering plateform piezoelectric elements 17-22 of the same piezoelectric constant and thickness expanding and contracting according to impressed voltage via conductive adhesive in such a manner that electrodes 11-16, 23 are positioned on both surfaces of each piezoelectric element. A conductive shim should serve as the electrode 23. The direction of polarization (arrow) of the piezoelectric elements 17-19 on one side of this shim 23 and the direction of polarization (arrow) of the piezoelectric elements 20-22 on the other side are both toward the shim 23. A voltage of strength nearly proportional to the distance from the center of thickness of the main body of piezoelectric actuator to the center of thickness of each piezoelectric element 17-22 is impressed on said element 17-22 of the main body of bending type piezoelectric actuator thus constructed.

Piezoelectric pressure indicator

Abstract: In a piezoelectric pressure indicator comprising a casing, a pressure receiving member at the bottom of the casing, piezoelectric elements mounted on the pressure receiving member, an acceleration compensating weight and acceleration compensating piezoelectric elements, both piezoelectric elements being connected such that the voltage produced thereby cancel with each other, thereby compensating for an effect of acceleration, an uppermost acceleration compensating element is formed with a perforation, and a lead wire for deriving the voltage is connected to the electrode of a lower imperforate acceleration compensating piezoelectric element to extend through the perforation of the imperforated element. In a modification, the pressure receiving member is covered by a heat resistant protective layer made of ceramic.

Preparation and placing of coaxial piezoelectric sensors in a roadway

Abstract: Piezoelectric sensor for the dynamic weighing and detection of vehicles on a roadway. The sensor is integral with a metal frame which is symmetric with respect to its axis and placed in a trench perpendicular to the traffic flow direction. The trench is filled with a material allowing as great a mechanical decoupling as possible between the sensor and the roadway.

Ultrasonic imaging with an electron beam scanned PVdF sensor

Abstract: Reflection and transmission ultrasonic imaging can be achieved with high resolution and in real time when a monolithic piezoelectric sensor is scanned by an electron beam in vacuum. For many years, a half-wave resonant X-cut quartz crystal has provided the best compromise of resolution, sensitivity and vacuum compatibility. In this presentation the substantial improvement in image quality derived from the use of an electroactive PVdF sensor and its performance in high vacuum are discussed in terms of a detailed analysis of the way in which the acoustic wave enters the sensor plane and spreads by the multiple reflection process. Representative images obtained by reflection and transmission using both types of sensor are compared.