Showing papers on "Piezoelectric sensor published in 1986"

Method and apparatus for measuring viscosity in a liquid utilizing a piezoelectric sensor

Abstract: A piezoelectric element energized to exhibit thickness-shear mode vibration is utilized to measure the viscosity of liquids. Electrodes, of an inert material are bonded to the major faces of the disc shaped crystal and are of a lesser diameter than the crystal surfaces so as to provide a concentric ring area of the crystal that is unenergized.

Alarm for a blind

Abstract: An alarm device, suitable for use with venetian blinds and other retractable blinds and curtains, comprises, secured together as a single unit, a piezoelectric motion sensor, an amplifier circuit electrically connected to the piezoelectric sensor to amplify signals generated in the sensor, an audible alarm electrically connected to the amplifier circuit for activation by the amplified signals, and a source of electrical power for the circuit and the audible alarm. In one embodiment described, the unit is built upon a printed circuit board and is of such shape and dimensions as to fit in the bottom rail of a venetian blind.

Stacked type piezoelectric actuator

Abstract: A stacked type piezoelectric actuator comprises a main stack of a plurality of electrostrictive strain elements stacked one on another. Each strain element comprises a first piezoelectric element plate having a first direction of polarization and a second piezoelectric element plate having a second direction of polarization. An end electrostrictive strain element is mounted on an end of the stack and has a lower shear strain component during widthwise expansion and contraction of the actuator. The end element includes either a stack of two or more of the first piezoelectric element plates or a pair of first and second piezoelectric element plates when the first piezoelectric element plate has a piezoelectric strain constant d 33 that is less than the strain constant d 33 of the first and second piezoelectric element plates in the main stack.

The effect of electrode stiffness on the piezoelectric and elastic constants of a piezoelectric bar

Abstract: Electrodes that are stiff and thick compared with the underlying piezoelectric substrate material can substantially change the effective piezoelectric and elastic constants from those values which would be obtained in the absence of electrodes. A simple analytical model for the stress distribution inside a composite piezoelectric plate, consisting of two outer electrode layers and one inner piezoelectric layer, is used to calculate the effective g31, g32, and g33 piezoelectric constants, as well as the effective sij (i, j = 1,2,3) elastic compliance coefficients. Numerical results for copper‐clad poly (vinylidene) fluoride (PVDF) plates are presented. [Work supported by the Office of Naval Technology and by Raytheon Submarine Signal Division, Acoustic Transduction Research and Development Project (DR).]

Electronic animal hoof force detection systems

Abstract: Hoof force detection apparatus having shoe portions adapted for connecting to the hooves of hoofed animals. The apparatus also includes piezoelectric elements mounted on sensor mounting sections which are connected to the shoe portions using flexion joints. The flexion joints allow forces applied to the animal's hooves through the shoe to be accommodated without applying undesirable bending moments and shear forces which would render output signals from the piezoelectric elements unreliable. Preferred forms of shoe-transducer structures include a plurality of spokes extending from shoe portions to centrally positioned sensor mounting sections. Other forms have sensors mounted in the shoe portions. The piezoelectric sensor structures preferably include a ceramic piezoelectric element protected by a cap having a flange. The protective cap and piezoelectric element are held in place by a mounting ring in some preferred embodiments. Backup plates can be used to properly support the sensor structures. Also disclosed is a signal amplication and integration circuit for analyzing the output signals produced by the piezoelectric elements and similar sensor types. The circuits include current-to-voltage conversion, voltage-to-frequency conversion and digital counting.

Piezoelectric valve and its driving method

Abstract: PURPOSE: To obtain a sufficient pressing force by making both a mechanical deflection force and a force produced by an electric field of the same direction with that of residual polarization of a piezoelectric deflection element work on a valve piece. CONSTITUTION: When a valve piece 22 is closing an input port 24, piezoelectric deflection element 6 is forcibly made to deflect mechanically upward. Between leads 19 and 20 is applied a voltage with the side of the lead 19 positive to produce an electric field of the same direction with that of residual polarization in a piezoelectric plate 11. This produces a contraction force only in the piezoelectric plate to produce a downward force at a free end of the piezoelectric deflection element 6 due to the contraction force of the piezoelectric plate 11. Thus, the valve piece 22 closes the input port 24 by means of the piezoelectric element 6. COPYRIGHT: (C)1987,JPO&Japio

Ultrasonic wave transmitting and receiving device

Abstract: PURPOSE:To attenuate the oscillating operation of a piezoelectric sensor speedily and to measure a short distance by providing an impedance control means which lowers circuit impedance viewed from the piezoelectric sensor. CONSTITUTION:A saw-tooth pulse voltage signal is supplied from a turning-on circuit 14 to a light source 13 at the end time t1 of transmitting operation, and the light emission intensity decreases after the light source turns on at a point t1 of time. On the other hand, light from the light source 13 is supplied to a photoconductor 11 and its resistance value which is considered to be infinite drops abruptly at the point t1 of time. Therefore, the energy accumulated in the sensor 2 during the transmitting operation is discharged through the impedance varying means 10 of an impedance control means 9 and the oscillating operation of the sensor 2 is converged on the zero level speedily. For the purpose, the received signal of a reflected wave from a target which is at extremely short distance is detected securely to measure the distance.

Piezoelectric weighing device

Abstract: A piezoelectric device is used to determine the absolute weight of an unknown sample by comparison to a control sample whose weight is known. A piezoelectric driver is resiliently attached to a base that is isolated from vibrations. A piezoelectric receiver and a reed are resiliently attached to the piezoelectric driver so that (1) the reed is moved in response to motion of the piezoelectric driver, and (2) the piezoelectric receiver gives an electric signal out proportional to motion of the system. The entire system is set to operate on the leading edge of the resonant frequency for the system. By applying an oscillating sine wave voltage, such as 140 hertz, to the piezoelectric driver, and by applying a known mass to the tip of the reed, a first output is obtained from the piezoelectric receiver which represents the calibrated weight. Next by exchanging an unknown sample for the known mass, a second output is obtained that represents the second weight. By a ratio of the second output/first output (or a signal equivalent to the weights being measured), the absolute weight of the unknown sample is determined.

Robot Gripper Control System Demonstrating PVDF Piezoelectric Sensors

Abstract: A novel robot gripper control system is presented which uses PVDF piezoelectric sensors to actively damp exerted force. By using a low-input-resistance amplifier to sense the currcnt devclopcd by the PVDF sensor, an output proportional to the rate of changc of the force exerted by the gripper is obtaincd. The signals from the I'VDF sensor and a strain gauge force sensor are arranged in a proportional and derivative (I'D) control system for the control of force. The control system was tested o n an instrumented Rhino XR-1 manipulator hand. 7'he capabilities of the control system are analyzed analytically, and vcrificd experimentally. The rcsults for this particular gripper indicate that as much as 900% bprovcmcnt in force stcp response rise time, and 300% reduction in overshoot are possible by inclusion of the PVDF scnsor.

Principle op piezoelectric damping of vibration: an experimental investigation

Abstract: Since the vibration behaviours of a piezoelectric vibration system change with an electrical load, the Vibration of such a system will be damped, when the electrical load includes a resistance component Based on this effect, a principle of piezoelectric damping of vibration is developed In this paper, piezoelectric damping configurations for both thickness and longitudinal vibrations are experimentally studied The results show that the piezoelectric material may become a new type of material for damping and the piezoelectric vibrator can be used as a new type of damper The piezoelectric damping adjustment is convenient and can be carried out continuously and instantaneously

Eignmodes of piezoelectric lenses

Abstract: The generalized expressions obtained for calculating eigenfunctions of harmonic and nearby anharmonic modes of a PEL make it possible better to direct the search for optimal resonator geometry. These functions enable us to compute such equivalent dynamic parameters of resonators as the inductance, capacitance, capacitance ratio, and others. They also enable us to determine resonator sensitivity to a localized change in PE thickness, which is proportional to the square of the eigenfunction; this is necessary not only in the manufacture of resonators, but in the construction of various kinds of piezoelectric sensors as well.