Abstract: The invention relates to an arrangement for remote ultrasonic temperature measurement. The arrangement employs a sensor, which in turn comprises an electromechanical transducer, a sensing element, and a hollow ultrasonic waveguide for coupling the sensing element to the transducer. The transducer is designed to propagate surface waves of a torsional or a radial shear mode upon the internal surface of the waveguide. The walls of the waveguide are made sufficiently thick, such that supporting clamps applied to the exterior of the waveguide have no adverse affect on interior wave propagation. The sensing element may be of either a hollow construction using internal surface wave propagation for protection of the active interior surface of the sensing element or of a solid construction in which the active outer surface of the sensing element may be exposed to the environment.

Abstract: The invention relates to an arrangement for ultrasonic temperature measurement. The arrangement combines an ultrasonic temperature sensor and an electronic operating circuit. The ultrasonic temperature sensor comprises an acoustic waveguide, a second acoustic wave propagating resonant element, which is exposed to the thermal conditions under measurement, and whose resonant frequency becomes an indication of the temperature, and decoupling means inserted between the waveguide and the resonant element to facilitate high "Q" operation of the sensor. The arrangement utilizes torsional waves if a solid waveguide is employed, or internal surface waves with axial symmetry if a hollow waveguide is employed. The sensor is excited by a pulsed CW source, whose carrier is retuned to the resonant frequency of the sensor, and measured as the indication of temperature. The electronic operating circuitry achieves improved accuracy in temperature measurement as the "Q" of the sensor increases.

Abstract: A datum is disclosed for use as a coordinate reference in a numerically controlled machine tool. The datum which is active, consists of an elongated member, typically one half wavelength in length, supported at its center (and antinode) by a plate, and including electromechanical transducers for exciting resonance in a desired fundamental longitudinal mode. The datum is operated by an operational amplifier having the transducers connected in the amplifier feedback path. Assurance against the excitation of undesired modes is achieved by limiting the gain of the operational amplifier throughout the response band of the transducers, by use of an inductor for resonating the input capacitance of the driving transducer at the frequency of the desired mode and by gain bandwidth limits of the operational amplifier. The datum is active at an ultrasonic frequency suited to touch sensing and thus produces a response in a touch sensing system when the cutter is touched to the datum.

Abstract: The invention relates to hydrophones which require liquid backing of the sensing plate, and more particularly, to compliance enhancing means for use in such hydrophones. In a practical embodiment, in which a compliant sensing plate in the form of a thin diaphragm is employed, liquid backing of the sensing plate is provided to balance the hydrostatic pressure across the sensing plate. To increase the compliance of the hydrophone, reduced by the presence of the backing oil, and to do so in a linear manner, a bellows is introduced into the backing chamber having the desired compliance and pressure rating. The invention is applicable to hydrophones having either compliant or stiff sensing plates. An improvement in hydrophone linearity and sensitivity is obtainable over a significant range of hydrostatic pressures.

Abstract: An immersible liquid densitometer is disclosed employing an immersible vibrator. The vibrator includes one or two masses which are resiliently supported and which contain perforations which fill when the vibrator is immersed in the liquid. When the vibrator is immersed, the frequency of vibration is affected in proportion to the density of the liquid filling the perforations. Thus, measurement of the frequency of vibration may be used to determine the density of the immersing liquid. For maximum accuracy, the configuration and vibratory mode of the masses are selected for minimum energy coupling to the liquid. Typically, a cylindrical configuration is selected vibrating in a rotational mode. Under these conditions, the drag during vibration is due primarily to skin friction and a high Q, high accuracy measurement is achieved.

Abstract: The present invention relates to a transducer array having a resolution suitable for imaging objects disposed in a liquid medium and illuminated with sonic energy of short wavelength. The array consists of a plurality of piezoelectric transducers sensing the sonic waves at their extremities and designed to produce corresponding electrical voltages suitable for image formation. While the individual transducers are fabricated from a common monolithic block, a geometry is used which reduces the coupling between the individual transducers. The individual transducers, which vibrate in a longitudinal mode with antinodes at either extremity and nodal regions at the center, are supported at their nodes by a thin web. The thin web then is the means for attaching the array to the frame of the apparatus. Central nodal support of the transducers minimizes stresses on the web from transducer vibration, reduces crosstalk, and improves the resolution of the array.