Abstract: A position sensor for measuring the distance from a first position to a second position. The sensor may include an elastic wave generator, an acoustical path over which the elastic wave passes, and a transducer to which the wave passes. A measurement loop includes the acoustical path, and has electrical and optical elements. The electrical elements may compare the phases of the transducer signals from which the change in position between the first and second positions are determined. Alternatively, the measurement loop may comprise a feedback loop to produce oscillations and an output frequency. A frequency counter is included in the feedback loop to measure frequency.

Abstract: A position sensor for measuring the distance from a first position to a second position. The sensor may include an elastic wave generator, an acoustical path over which the elastic wave passes, and a transducer to which the wave passes. A measurement loop includes the acoustical path, and has electrical and optical elements. The electrical elements may compare the phases of the transducer signals from which the change in position between the first and second positions are determined. Alternatively, the measurement loop may comprise a feedback loop to produce oscillations and an output frequency. A frequency counter is included in the feedback loop to measure frequency.

Abstract: An instrument is provided for measuring the temperature of an object from infrared radiation emitted by the object. The instrument includes a radiation detector, a temperature indicating device connected to the detector, and a modulator disposed in a path of a radiation beam from the object for converting the beam into a series of pulses when the modulator is vibrated in and out of the path. The modulator includes a primary piezoelectric element adapted to vibrate when subjected to driving signals at a frequency related to the resonant frequency of the modulator, and a secondary piezoelectric element connected with and driven by the primary piezoelectric element. The secondary piezoelectric element is electrically insulated from the primary piezoelectric element. The modulator also includes a blocking element connected with the secondary piezoelectric element and disposed to move in and out of the path of the beam.

Abstract: The invention relates to a method and apparatus for the generation of low frequency sound by means of the excitation of a low frequency standing gas borne sound wave. A low frequency sound generator comprises a resonator part and a feeder part with a feeder unit. The method consists of a controlled generation of periodic changes of the gas volume of the resonator part in order to create a standing sound wave. The invention also includes a feeder unit for the working of the method. The feeder unit comprised of three rotating parts, namely one center rotor and two side rotors, the rotation of which are synchronized. The feeder unit is open on two sides, each side communicating with one tubular resonator. The rotors are provided with cut out portions and the center rotor is also provided with a protruding vane-shaped part.

Abstract: The invention relates to a frequency controlled motor driven low frequency sound generator. The low frequency sound generator consists of an open resonator (2) arranged as a sound emitter for generating standing gas-borne sound waves which produce a varying gas pressure inside the resonator, and a feeder unit (1) for a modulated supply of air pulses to the resonator. The feeder unit (1) comprises a motor driven piston (8) with an approximately sinusoidal volume velocity. The piston is mounted on a piston rod (7) which is connected to a flywheel (6). The flywheel, in its turn, is mounted on a shaft (5) which is driven by a motor (3). The motor speed and thereby the frequency of the piston is regulated by a special electronic control unit.

Abstract: An arrangement for generating natural resonant oscillations of a mechanical oscillating system includes an electromechanical oscillation exciter which on excitation by an electrical excitation signal generates a drive force setting the oscillating system in mechanical oscillations, an oscillation sensor which is formed as displacement sensor and senses the mechanical oscillations of the oscillating system and converts them to an electrical sensor signal, and an excitation circuit which receives the sensor signal and supplies to the oscillation exciter the electrical excitation signal with the frequency of the sensor signal. The excitation circuit includes a phase control circuit which controls the phase position of the excitation signal in dependence upon the phase position of the sensor signal. A phase shift circuit produces a phase displacement of 90.degree.

Abstract: The resonator (10) includes a monocrystal (11) of a nonpiezoelectric matel with low attenuation of elastic bulk waves, such as corundum, means of supporting the monocrystal fastened to the monocrystal at points corresponding to the vibration nodes, thermal means (40) for directly causing a proper excitation of the monocrystal (11) and optical means (50) for detecting the periodic motion of the resonator without contact. Application in particular in oscillator construction.

Abstract: There is described a system for producing noise particularly for sonic testing of an article, such as a satellite, in a reverberation chamber. In one of its aspects the system comprises a low frequency high-level broad-band noise source; a tube means including a section formed as an acoustic horn connected at its small end to the low frequency source and at its large end to the chamber. A Hartmann-type air acoustic high level noise generator, or generators are located inside the tube at a predetermined position. In operation the generator is excited by the generated low frequency noise to provide an output of non-linearly modulated noise. Also described is a Hartmann-type noise generator which comprises a nozzle and an aligned acoustic tube spaced therefrom by an air gap. A reverberation cup is formed in the mouth of the tube facing the nozzle and a bridge member extends between the nozzle and tube and spans the air gap.

Abstract: A resonator device comprises an elastic beam driven electrostatically at its natural frequency, or an harmonic thereof, by voltage pulses applied to an integral paddle member. The voltage pulses are derived from optical pulses fed via an optical fibre and reflected from the paddle member to a photodiode array. There is thus minimal coupling between the beam and the drive system. A positive feedback loop is provided in which light retroreflected from the paddle member is recaptured by the optical fibre and electronically detected, amplified and fed back in phase with the beam oscillations by modulating the optical pulses.

Abstract: A slide switch is movable in the direction of oscillation of the reed of a magnetic circuit. A resilient arm is attached at one of its ends to the switch. The slide switch drives the arm in the direction of the oscillation of the reed, the motion of the arm being in a plane parallel to the oscillation path of the reed but removed from it. A ramp is located adjacent the opposite end of the arm and intersects the plane of the oscillation path of the reed, one end of the ramp engaging the opposite arm end at its equilibrium position and the other end of the ramp extending well into the plane of the oscillation path of the reed.

Abstract: In an ultrasonic system for detecting and distinguishing between superimposed and single sheets moving along a transport path, the frequency of the ultrasonic source is kept tuned to the natural frequency of the total system so that the phase displacement detected when a sheet-like object is present between the source and the ultrasonic receiver represents characteristics of the object itself. When no sheet-like object is present the receiver and the source are connected in a feedback circuit producing a certain natural frequency comparable to that which occurs with proximities between a microphone and a loud speaker, and the frequency of an oscillator is tuned to this natural frequency. When a sheet-like object is present the tuned oscillator frequency is applied to the ultrasonic source and its phase is compared with the phase of the ultrasonic signal at the receiver.

Abstract: A sonic agglomeration system wherein high sound intensity and resonance are maintained with a low power input. These functions are attained through the use of a chamber feed-horn design that promotes resonance and maximized the efficiency of sound transfer between a sound producing compression driver and a resonant chamber. A digital controller maintains efficient resonance in the chamber and an efficient agglomeration rate constant by making adjustments in the frequency, sound amplitude and nuclei injection rate of the system.

Abstract: A thermometer is provided for remotely measuring the temperature of a heat source. The device utilizes an infrared sensor for detecting the temperature of a remote object and an output of the sensor is processed and used to drive a meter or other display device. An improved resonant circuit is provided for modulating the radiant energy impinging on the sensor to produce a pulsed output from the sensor. The modulating circuit includes a piezoelectric reed which deflects under an applied frequency and is located in the optical path of the system. The reed serves as an active element in an improved phase-locked loop used to drive and stabilize the optical chopper.

Abstract: An oscillator for operation in the frequency range from about 2 GHz to at least 18 GHz using a magnetostatic surface wave delay line as a frequency control element in a feedback loop connected around an amplifier. The oscillator is tunable by varying the magnetic field intensity at the magnetostatic surface wave propagating medium and by varying the distance between input and output rf couplers along the propagation surface.

Abstract: A temperature compensated surface acoustic wave device having an SiO.sub.2 film layer upon a substrate of piezoelectric material. The positive temperature coefficient of delay of the piezoelectric substrate is counterbalanced by the negative temperature coefficient of the SiO.sub.2 layer. The thickness and shape of the SiO.sub.2 layer are chosen to give a zero first order temperature coefficient for the composite device. Lithium niobate and lithium tantalate are preferred piezoelectric materials for the substrate. A high degree of temperature stability is thereby obtained with coupling coefficients much greater than were previously obtained by prior temperature compensated surface acoustic wave devices.

Abstract: A surface acoustic wave oscillator comprises a surface acoustic wave delay line and amplifier. The phase difference between signals received from two transducers on the surface acoustic wave delay line is measured by a phase sensitive detector whose output is used to control a phase correction circuit. The oscillator may oscillate at a steady frequency or be frequency modulated.