Abstract: A method and apparatus for pre-straining a bolt-on strain sensor. The pre-strain is preferably adjusted by inserting a strain adjusting tool through strain adjusting holes in the sensor and the structural member. The portion of the tool engaging the sensor is preferably offset from the portion of the tool engaging the hole in the support structure to provide a camming function. After the strain has been adjusted to a desired value, a bolt adjacent the strain adjusting hold of the sensor is tightened to fixedly secure the sensor to the support structure and maintain the preadjust strain at the desired value.

Abstract: An acoustic ranging system monitors the level of material inside one or more vessels. The system includes an ultrasound transducer mounted in each vessel that is connected to a transmitter and a receiver through a transmit/receive isolation switch and a multiplexer. The transmitter applies a transmit signal to the transducer responsive to a trigger signal generated by a processor thereby causing the transducer to generate an ultrasound signal. An electronic receiver coupled to the transducer generates a receive signal responsive to the reflections of the ultrasound signal from the material. The receive signal is coupled to the processor which determines the elapsed time interval between generating the trigger signal an receipt of each receive signal. The processor then converts one of the elapsed time intervals into a distance indication corresponding to the level of the surface of the material.

Abstract: A load measuring system specially adapted for installation on the support legs of existing storage vessels. The load measuring system includes an attachment plate that is fastened to each support leg of the vessel, a support plate that is mounted on anchor bolts projecting upwardly from the supporting surface, and a load cell positioned between the attachment plate and the support plate. The support plate is supported by nuts threaded on respective anchor bolts. The nuts are rotated to raise the lower ends of the support legs above the supporting surface, thereby transferring the portion of the vessel's weight carried by the support leg to the load measuring system. The space between the support plate and the supporting surface is then filled with a supporting material such as concrete.

Abstract: A bolt-on strain sensor includes an L-shaped sensor body having a mounting hole formed at the end of each leg of the L-shaped body and a mounting hole formed at the intersection of the legs. A first strain sensing structure is formed in the sensor body between two of the mounting holes and a second strain sensing structure is formed in the sensor body between the other two mounting holes. The strain sensing structure is preferably a strain gauge instrumented measurement beam connected to the sensor body on opposite sides of the strain sensing region by spaced apart interconnecting members. A printed circuit board on which a plurality of electrical components are mounted is secured to the sensor body with a suitable fastener. A cover is then placed over the sensor body and printed circuit board.

Abstract: An ultrasound transducer includes a resonant driving assembly having an ultrasound radiating surface covered with a propagation disc of impedance matching material. The resonant driving assembly and propagation disc are housed in a polymeric or stainless steel enclosure. All exposed surfaces of the enclosure, resonant driving assembly, and disc are covered with a coating of polyparaxylylene to make the transducer substantially impervious to industrial chemicals.

Abstract: A load cell adapted to be positioned between a foundation and each of several support members for a storage vessel. The load cell includes a circular flex plate having a pair of concentric cylindrical members of different diameters secured to opposite surfaces. A mounting pad adapted to be fastened to the foundation is secured to one of the cylindrical members. A mounting plate is secured to the other cylindrical member. The mounting plate has either a single threaded bore or a threaded stud positioned at the common axis of the cylindrical members for securing the mounting plate to a vessel support member. A strain sensor mounted on the flex plate measures the load-induced deflection of the flex plate.

Abstract: A strain sensor is provided which includes a base member and a pair of mounting points for mounting the base member to a support structure supporting a vessel for weighing the contents of the vessel. The base member defines a cylindrically shaped well located at the center of base member. The area of the base member within the well defines a pair of apertures symmetrically located on opposite sides of a central longitudinal axis of the base member. The base member also defines a pair of notches located on opposite edges of the base member which run parallel to the longitudinal axis of the base member. An axial strain sensing element is mounted in the well along the longitudinal axis of the base member for sensing the axial strain in the support structure. In addition, a transverse strain sensing element is mounted in the well perpendicular to the axial strain sensing element for detecting strain a direction transverse to the longitudinal axis of the base member.

Abstract: An isotropic strain sensor having four mounting points interconnected by four legs, two of which are bowed toward each other and two of which are bowed away from each other. A strain sensing element mounted on at least one of the legs provides an electrical indication of the deflection of the leg. As a result, the strain sensor measures isotropic strains in an object to which the strain sensor is attached through the mounting points. Another embodiment of the strain sensor utilizes three mounting points interconnected by legs, two of which are bowed outwardly and one of which is bowed inwardly. Both embodiments of the strain sensor produce outputs that are a nonlinear function of the sensed isotropic strain. This nonlinear characteristic allows the strain sensor to provide an output that is a linear function of the load applied between the center and outer periphery of a freely supported disc that has a strain that is a nonlinear function of the applied load.

Abstract: An extensometer having two spaced-apart mounting bases adapted to be mounted on a load-bearing structure with its axis of sensitivity intersecting the axis along which load-induced strains are generated at 45.degree.. The extensometer includes a pair of parallel links connecting the mounting bases through respective flexure hinges. In one embodiment, one of the links is also connected to one of the bases through an intermediate flexure hinge so that the link deforms responsive to relative movement applied between the bases along the axis of sensitivity. A strain gauge mounted on this link measures the magnitude of the deformation. In a second embodiment, a strain-instrumented measurement beam extends between the two links so that it deforms responsive to pivotal movement of the links as the mounting bases move in opposite directions along the axis of sensitivity. This embodiment of extensometer may be mounted on the load-bearing structure through three or more mounting points.

Abstract: A load cell having a parallelogram configuration formed by a pair of spaced-apart, generally parallel force-receiving members interconnected by a cantilever beam and a parallel spacer beam. The cantilever beam projects perpendicularly from one of the force-receiving members, and its end is secured to the other beam by a flexure hinge. The ends of the spacer beam are secured to the force-receiving members by respective flexure hinges. In order to maintain the parallelogram configuration of the load cell, the length of the spacer beam is equal to the length of the cantilever beam from the beam's virtual pivot point to its end. Rotational moments imparted to the force-receiving members apply forces to the beams along their longitudinal axes without deflecting the cantilever beam, thus making the load cell insensitive to such moments. A reduced thickness portion instrumented with semiconductor strain gauges is formed in the cantilever beam near its point of attachment with the force-receiving member.

Abstract: A load disc having an annular flex plate connected to a pair of parallel mounting plates through respective support rings. The support rings are of unequal diameters so that compressive or tensile forces applied to the mounting plates cause the flex plate to spherically deform. The deformation of the flex plate produces tensile and compressive strains on opposite faces of the flex plate which are measured by strain gauges mounted on opposite faces of the flex plate. The flex plate is recessed away from the support rings at the points of attachment thereto so that the support rings intersect the flex plate at its neutral plane. Consequently, spherical deformation of the flex plate does not tend to expand or contract the support rings thereby allowing freer deformation of the flex plate and desensitizing the flex plate against lateral forces applied between the mounting plates.

Abstract: A strain sensor or extensiometer with electrical output designed to measure relative displacements between two axially spaced points on a stressed structure comprising an elongated body with two end sections and a centrally located flexible beam extending in a direction perpendicular to the longitudinal axis of the sensor body. Relative displacements of the end sections generate two opposing symmetrical torques at the ends of the beam. These torques or bending moments are impressed onto the beam through two sets of flexible bridges which are symmetrically located but unequally spaced on opposite sides of the beam. These two torques or couples cause the beam to bend evenly over its entire length. Resistance strain gages bonded to both sides of the beam at its center measure this bending.