Showing papers on "Piezoelectric sensor published in 1980"

Piezoelectric snap actuator

Abstract: A piezoelectric actuator including a piezoelectric element; a snap-action device for exerting a positive force in opposition to the piezoelectric element and having a predetermined reaction force that must be overcome to cause the snap action; the piezoelectric element including piezoelectric means for providing an opposing force to the snap-action device in excess of the reaction force; and means for applying an electric field to the piezoelectric means to enable it to generate the opposing force and store energy in the snap-action device to enable occurrence of the snap action.

Piezoelectric vibrator with damping electrodes

Abstract: A piezoelectric vibrator includes an elongated piezoelectric plate deposited with electrodes for effecting mechanical vibration in the piezoelectric plate. A damper is deposited at each of opposite ends of the elongated piezoelectric plate so as to reduce the size of the piezoelectric plate.

Monitor for spindle of drilling machine - has piezoelectric sensor on shank of drill to measure radial and axial forces

Abstract: The monitor for tool breakage, wear and control uses a sensor subjected to the cutting force. The sensor exploits the piezoelectric effect and is located on the shank of the drill at the place where it joins the machine's spindle. The sensor is normal to the axis of the drill. The sensor measures the radial force exerted on the drill or it may be located so as to measure both radial and axial forces. The electrical signal from the sensor is passed to evaluating circuitry that compares the sensor's signal with a stored set of references. The comparator's output is displayed or passed to the machine tool's control unit.

Oscillator with a feedback circuit employing a pre-polarized ceramic piezoelectric oscillating unit

Abstract: A feedback circuit for use in an oscillator has a piezoelectric oscillating unit constituted by a square plate-like piezoelectric body, first and second electrodes provided on one surface of the piezoelectric body and a common electrode provided on the other surface of the piezoelectric body. The piezoelectric body is polarized in one direction between the first and common electrodes and in the opposite direction between the second and common electrodes.

Shape-Dependent Damping in Piezoelectric Solids

Abstract: Absrruct-The piezoelectric contribution to the mechanical loss tangent of a piezoelectric solid is derived from its complex piezoelectric and dielectric coefficients. This loss depends on specimen geometry as a result of differences in effects related to the electrical boundary conditions. Inclusion of a positive out-of-phase piezoelectric modulus results in reduced values of the predicted loss, which constitutes an improvement Over earlier theories which predict losses exceeding measured losses by a factor greater than two.

Nonlinear charge release of piezoelectric ceramics under uniaxial pressure

Abstract: The charge release of piezoelectric ceramics under uniaxial pressure is in strong contrast to the behaviour of nonferroelectric piezoelectric materials (e.g., quartz). The piezoelectric constant d depends on the applied pressure and on the prehistory of the sample. The charge-stress characteristics is strongly nonlinear and shows hysteresis. Some piezoelectric ceramic materials exhibit a “strain memory”. The charge-stress curve of these materials shows a pronounced dip when a previously applied stress is reached. The effects of nonlinearity, hysteresis and strain memory are explained as being due to domain wall motion and fixation of domain walls at the grain boundaries and/or within the grains.

Blood pressure monitor using arterial tonometer method - has two piezoelectric sensors monitoring artery expansion and compensating for movement of patient

Abstract: The blood pressure monitor employs a cuff with two piezoelectric sensors, that are pressed firmly against the skin where the artery runs under the latter. One of the sensors displays the variable expansion of the artery, while the other sensor, which is coupled in electrical opposition, provides a signal for compensating the movement of the patient. The two sensors are supported by mechanically separate membranes, e.g. thin metal plates, each conductively connected to a surrounding stable metal frame. Each sensor comprises a piezo-oxide chip, one with its negative pole attached to its membrane and the other with its positive pole attached to its membrane. Each chip has a soldered contact for a signal lead. The cuff is pref. filled with air to force the sensors into contact with the skin, or alternatively the sensor may be attached to a wrist band similar to a watch strap.

Ultrasonic holography imaging device having a macromolecular piezoelectric element transducer

Abstract: An ultrasonic image device such as may be used in a holography system or scanning system and having a piezoelectric transducer in which the conversion efficiency and phase are substantially constant over a wide frequency range. A piezoelectric sheet 5 μm to 1000 μm thick is used for a piezoelectric element. The piezoelectric sheet is constructed of a macromolecular material including polymers and copolymers of polar monomers. A high frequency signal input device applies to the electrodes coupled to the piezoelectric sheet high frequency signals of different frequencies in a range around a fundamental resonance of the piezoelectric sheet of ±10 to ±70% of the fundamental resonance frequency.

piezoelectric yarn break detector - removably mounted in lappet in slots with electric connecting leads in slots

Abstract: A piezoelectric sensor attached to yarn guide acts as a yarn back detector. The piezoelectric sensor and yarn guide are mounted in a cylindrical holder on a tappet. The electrical leads to the sensor are on each side of the holder and wires mounted in slots in the holder extend towards the tappet mounting. The piezoelectric sensor easily distinguishes yarn generated vibrations from spinning machine vibrations, and signals from many sensors are easily collected and monitored. Operator monitoring of the machine is reduced. The lappets are fitted to ring spinning machine.

Amplitude distribution of pulses produced by shock waves due to cavitation bubbles

Abstract: The authors study the amplitudes of the pulses delivered by a piezoelectric sensor immersed in a cavitation field A 1024‐channel analyzer shows that the amplitude distribution of these pulses includes peaks They go on to show the pattern of evolution of this distribution as a function of the ultrasonic power and the distance between the piezoelectric sensor and the transducer

Transduction with PVF2 in the Ocean Environment.

Abstract: : Experimental methods were utilized to establish the piezoelectric properties of PVF2, in the one-dimensional (33-mode) and hydrostatic mode of operation. The coupler reciprocity method has been used for characterizing the PVF2 as a hydrophone and as a transmitter. This method gives the free-field voltage sensitivity and hence g-the piezoelectric voltage coefficient. Through K(supra T) sub 33 the relative dielectric constant, d-the piezoelectric strain coefficient is obtained. Measurements in the one-dimensional configuration were taken at 100 and 1000 Hz in the stress range 0-100 MPa, and at four temperatures: 40, 25, 15, and 3.5C. Measurements in hydrostatic configurations were taken at 1000 Hz and at 25C. Samples prepared from the same sheet of PVF2 exhibit variations in piezoelectric activity, which are presented and discussed. A comparison method has been used to characterize the PVF2 as a dynamic pressure sensor; d was measured as a function of peak one-dimensional stress in the range 0-80 MPa and at four temperatures: 40, 25, 15, and 4.5C. The strain coefficient was also measured as a function of the rise time of the loading pulse at a temperature of 25C. The experimental results are shown and discussed. Comparison with typical ceramics and quartz transducers shows improved behavior of PVF2 over them.

Ultrasonic fuel injection quantity measurement for diesel engines - using frequency analogue signals and phase comparison circuit for output from piezoelectric sensors

Abstract: The fuel measurement device, is esp. for diesel engines and measures the quantity, pref. the mass, of fuel flowing through a tube(3) from a given time of the start of an injection cycle. Mechanical to electrical transducers measure the flow quantity and start time. The corresp. electronic signals are suitable for simple processing in a microprocessor. They are produced in frequency analogue form. An ultrasonic receiver(2), esp. a piezoelectric plate type, is placed downstream of an ultrasonic transmitter(1). An evaluation circuit compares the phases of the waves output from the transmitter and the signals produced by the receiver. The injection period finish time may also be measured. Calibration may be periodically performed in between injection cycles using the known flow speed to set a null.

Observation of Piezoelectricity in Thin Films Formed by Anodization

Abstract: Piezoelectric response has been observed in thin films of ZnO, ZnS, CuxS, Cu hySl and CuxZnyO formed electrochemicall y, by ano$ization, on metallic substrates. We have also observed piezoelectric response in anodized aluminum. been used to detect 10 MHz compressional ultrasonic waves, as well as low frequency signals. The anodization process used is inexpensive and fast, and could be used to deposit in situ piezoelectric sensors on almost any conducting solid. Measured film properties such as strength of piezoelectric coupling, growth rate, and surface morphology are discussed. These films have

Amplitude sensor for servo-control of loudspeaker - has piezoelectric sensor foil which responds to pressure variations in loudspeaker chamber

Abstract: An amplitude measuring instrument for feedback regulation of a loudspeaker of the type used in a headset, utilises pressure variations on a piezoelectric foil. The sensor (37) is located in the enclosed volume behind the loudspeaker diaphragm and is mounted on the speaker housing with a thin, isolating layer of an elastic material. A piezoelectric foil of polyvinyliden fluoride is located in the open end of a rectangular housing (38). The foil is pressurised by the vibrating air in the speaker chamber on the open side and a resisting force is provided by a foam material (44) on the other side. The foil is secured at the periphery by two retaining rings (401, 402). Both surfaces of the foil are metallised (42, 43) and these act as detecting electrodes providing signals on two output terminals (45, 46).