Abstract: EIS and EMIS methods of assessing the fatigue status of a material. The EIS method uses an electrochemical transducer cell to apply electrical perturbations to the material, and to acquire voltage and current measurements over a range of frequencies. The impedance at each frequency is calculated, resulting in impedance spectrum data. This data is correlated to reference data representing the fatigue life of the material. The EMIS method is similar except that mechanical instead of electrical perturbations are applied to the material.

Abstract: Strain of an object is measured by a bridge having, in one arm thereof, a strain gage for producing a resistance change depending on the strain developed in the object, and having resistors in the respective remaining three arms thereof. The resistors have respective resistances independent of the strain developed in the object. A pair of power corners are disposed at one pair of diagonally opposite joints, and a pair of signal corners are disposed at another pair of diagonally opposite joints of the strain gage. Strain is measured by detecting an output voltage between the signal corners of the bridge as an initial unbalanced output voltage e.sub.0 while no strain is being detecting by the strain gage, applying a power supply voltage between the power corners of the bridge, and detecting an output voltage e between the signal corners to detect strain of the object. Strain developed in the object is measured based on a value .epsilon..sub.

Abstract: A method and system for sensing surface contamination on an aircraft having a control surface. A control element including the control surface is connected to the aircraft by a hinge. The method and system sense a control surface hinge moment about a line on the hinge of the aircraft. A control surface steady hinge moment coefficient is calculated from control surface hinge moment data representing the hinge moment over a period of time. An unsteady hinge moment is calculated which is dependent on the control surface steady hinge moment coefficient. By using a value which is relatively constant during uncontaminated surface conditions, this value can be compared against calculated values to check for variations. If the calculated unsteady value varies from the known uncontaminated values, a warning may be given, alerting an operator of unsafe conditions. This warning is given before a critical value is reached, allowing the operator a period of time to react to the warning.

Abstract: Pressure sensitive inks have selected pressure sensitivity designed for use as a pressure sensitive component of a pressure sensitive device. The ink of the device is formed of an elastic polymer binder with a filler therefor of semiconductive nanoparticles preferably uniformly dispersed in the binder.

Abstract: A device for measuring compressive forces, comprising an annular body (1) having a pair of opposite, force-receiving front surfaces (2, 3) which are perpendicular to the central principal axis (4) of the body, and an annular cavity (5) essentially concentric with the principal axis and receiving a sensor means (6) for delivery of an electrical signal representing the force influence. The sensor means (6) comprises a sensor element (9) placed on the radially inner surface (7) of the cavity (5), said surface being situated at a distance from the principal axis (4) essentially corresponding to the radius (r.sub.R) for moment equilibrium for that part of the ring body (1) which receives a load.

Abstract: A method and system for calibrating a sensor is disclosed The method and system include receiving data relating to a plurality of temperature parameters and providing polynomial compensation of a temperature coefficient (TC). When providing polynomial compensation of the temperature coefficient, the method and system further include providing a first output and adding a second value to the first output. The first output is a distal temperature multiplied by a first value.

Abstract: A new strain/stress sensor based on the concept of reversible crack opening in a composite material. Crack opening increases the electrical resistance, which is the signal provided by the sensor. The new technology is manifested in concrete and mortar containing electrically conducting short fibers (e.g., carbon fibers and steel fibers). Carbon fibers serve to greatly decrease the crack height so that apparently reversible crack opening occurs. The crack opening is accompanied by fiber pull-out, resulting in fiber-matrix contact resistivity increase, thus allowing sensing under cyclic as well as static loading. A part of the resistance change is irreversible, so it provides memory of the first deformation.

Abstract: A force sensor including a cylindrical body having a central section and two distal sections wherein selected acoustic resonant modes are trapped in the central section and decays exponentially in the distal sections. An electromechanical acoustic transducer (EMAT) can be used to excite and detect the selected resonant modes in the central section. Force applied to the distal sections, including axial stress and torque, alter the resonant frequencies of the selected modes.

Abstract: A low cost, high bandwidth "smart skin" impact sensor is developed for application to vehicle side impact detection and diagnostics. The sensor is based on a piezo polymer smart skin technology and can sense impact location and impact energy in real time (i.e., fractions of a millisecond) along a vehicle side panel. The sensor is simple to manufacture, is low cost in production quantities, and can be used in concert with other devices in a sensor suite to provide, reliable, efficient, energy managed airbag development. With proper spatial shading techniques it is shown that the sensor can be designed also to report impact angle and the velocity of the impacting body.

Abstract: A force sensor comprising a substrate, a conductive material providing an electrically discernible response to compressive stress disposed on the substrate, and a thermocouple disposed on the substrate proximate to the conductive material. A measurement processor is also described that includes first means for measuring electrical signals from the conductive material indicative of compressive stress, second means for measuring electrical signals from the thermocouple indicative of temperature in proximity to the conductive material, means for determining a temperature compensating factor derived from the electrical signals indicative of compressive stress and the electrical signals indicative of temperature, and means for determining a temperature compensated compressive stress value derived from the temperature compensating factor and the electrical signals indicative of compressive stress.

Abstract: In a measuring arrangement comprising a strain gage section (10) constructed of at least one SG (strain gage) (15), and integrated in a measurement pickup (1), an additional circuit (20) amplifies modulated output signals of the SG section (10), and is also integrated in the measurement pickup (1). The measuring arrangement thus obtained is used for general measuring tasks, particularly for commercially available domestic or industrial scales including weighing devices operated by means of commercially available batteries. As an additional circuit, a modulation amplifier can be used which consists of a modulator constructed as squarewave generator, an alternating-voltage amplifier and a demodulator, the demodulator being a bridge rectifier composed of four electronic (on/off) switches or two electrical changeover switches.

Abstract: A device for counting and classifying load cycles in supporting structures with various loads, bridges, cranes, or tracks for example. A measuring instrument (2) is attached to an attachment side (7) of a load-cycle counter (1) and accommodates a mechanical strain amplifier (3). The ends (8 & 8') of the strain amplifier are much thicker and more resistant to strain. Its middle (9), which includes a strain gauge 10, is much thinner and more sensitive to strain. The ends are fastened to the attachment side. Any signal deriving from traction, force, or flection, and emitted by the strain amplifier (3) is forwarded through a digitalizer (4). The data are processed and stored in a signal processor (5).

Abstract: An apparatus and method for determining various physical quantities such as temperature, pressure, stress, strain, distance and the like in a manner such that a change in the physical quantity of interest results in a measurable change in the frequency of oscillation of a signal generated within the apparatus.

Abstract: A diagnosis system having sensors for supervising a plant, signal processors for processing signals of the sensors, and a state quantity arithmetic operation unit. The state quantity arithmetic operation unit calculates a quantity of state expressing the environment of the plant on the basis of supervisory information inputted through the signal processors. A state quantity prediction unit predictively calculates a quantity of state after a predetermined time on the basis of the quantity of state, supervisory information and a time change of the quantity of state inputted through the state quantity arithmetic operation unit. A future event prediction unit predicts a future event on the basis of predicted information of the quantity of state inputted through the state quantity prediction unit. An image information processor converts the quantity of state given by the state quantity arithmetic operation unit into image information and indicates the image information on a display unit.

Abstract: In measuring the stress of a ferromagnetic linear metal member, an alternating current is supplied to flow between a pair of terminals mounted to the ferromagnetic linear metal member to measure an impedance .vertline.Z.vertline. of the ferromagnetic linear metal member between the terminals by an analyzer. Then, a stress .sigma. is determined based on the measured value of the impedance .vertline.Z.vertline. from an impedance .vertline.Z.vertline.-stress .sigma. relationship possessed by the ferromagnetic linear metal member. The stress distribution in a sheet-like sensor can be likewise measured by inserting into the sensor a plurality of intersecting ferromagnetic linear metal members. The stress .sigma. is determined for each individual member as described above, and then the stress distribution in the sheet-like sensor is determined by summing up the stresses of mutually intersecting members.

Abstract: An electrical insulator having high mechanical strength is disclosed for use in connection with a force sensor body portion of a weld probe force gage. The force sensing body includes a pair of pockets for receiving a corresponding pair of welding electrodes. The pockets are lined with one or more anodized aluminum alloy inserts. Disposed upon each surface of each insert is a layer of oxide, which acts as an electrical insulator. The inserts are bonded to the receiving pockets so that one layer of oxide is internally disposed between the receiving pocket and the electrode. The force sensor body is fabricated from an aluminum alloy and anodized to form a second oxide layer between the receiving pockets and the inserts. The inserts protect the two oxide layers from external mechanical wear from welding electrodes.

Abstract: Apparatus for sensing the flexure of a surface includes an array of bistable dome shaped switches within the surface which change their state or position depending on the direction and degree of local flexure of the surface. A flexible sheet parallel to the surface carries wiring for detecting the state of the bistable switches and carrying this information to a computer. A second parallel sheet may be used to detect the second position of the bistable switches for extra accuracy. The bistable switches may be linked, meaning the perimeters of the bistable switches overlap, or unlinked. The two stable positions may include two oppositely protruding positions, or one protruding position and one flat position.

Abstract: A piezoelectric force sensor includes a piezoelectric plate, with one electrode on each of the top and bottom sides of the plate. One of the electrodes is electrically connected via a conductor to a contact pad. In the case that the piezoelectric plate experiences breakage, the conductor is broken, and the remaining residual capacitance of the conductor and contact pad becomes so comparatively small that the breakage can be reliably detected.

Abstract: A mechanical sensor is provided, which includes: a magnetic layer having permeability which is changed in accordance with stress generated therein; a coil having at least two terminals, allowing an electric current to flow therebetween to generate a magnetic flux, thereby magnetizing the magnetic layer; and a substrate integrally supporting the magnetic layer and the coil, wherein the coil is a planar coil including at least one winding, each winding having a U-shaped portion formed of a first conductive line portion, a second conductive line portion, and a connecting portion connecting the first and second conductive line portions, the first and second conductive line portions extending in a first direction, and impedance between the terminals is changed in accordance with a change of inductance caused by a change of the permeability of the magnetic layer.

Abstract: Apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user.

Abstract: A strain-gauge transducer (5) comprising a substrate (10) provided with strain gauges and pressure members (11, 12) which deform the substrate (10) via transfer elements (1a, 4a) which transmit an applied force (F). The transfer elements comprise bars (1a, 1b, 4a, 4b) molded from an elastomer in a common molding operation. A material (2a, 3a) having a higher compressibility than the bars may be interposed between the bars. This material may form elastic stops (54a) provided to preclude breakage of the substrate. This results in a transducer whose sensitivity is linear for small loads and which is very insusceptible to overloading. The transducer can be used for the construction of scales or touch tablets.

Abstract: In a veneer lathe having a knife mounted to a knife support frame with a backing plate, a roundup control system for a veneer lathe is disclosed that recognizes or detects the production of usable veneer using the body of the knife as a signal source. During initial production of veneer, the lathe produces a trash or roundup veneer that is directed to a chipper through a trashgate. When there begins production of usable veneer, the trashgate is closed and the usable veneer is directed toward production trays or stackers. A sensor or displacement detection device is mounted in the backing plate of the knife support frame lateral the unsupported portion of the knife. As the knife contacts wood, the unsupported span of the knife flexes causing the magnet to move which the sensor detects. The sensor outputs a voltage signal proportional to movement of the knife in magnitude and direction. This voltage signal is relayed to a central processing unit where it is converted into a digital signal.

Abstract: In accordance with the present invention, a tactile sensor capable of detecting shear force comprises an anisotropically conductive material disposed between a conductive cursor and an array of contacts. In one preferred embodiment, the anisotropic material is affixed to the contact array, and the cursor is affixed to an elastomeric skin overlying the material. Movement of the cursor is detected by interconnection of the contacts underlying the cursor. In a second embodiment, the anisotropic material is affixed to the cursor but is free to move over the contact array in response to shear force. Movement of the cursor is detected by interconnection of the underlying contacts. Such arrangements can also detect pressure and temperature.

Abstract: Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

Abstract: Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

Abstract: An electrical circuit containing novel piezoresistive sensor is disclosed. The sensor is connected to a source of direct current, and a stress of at least about 15 p.s.i. is applied to the sensor.

Abstract: A device for measuring physical variables comprises a pair of thin planar members disposed symmetrically in a face-to-face arrangement about a plane including a reference axis defining the direction of displacement of a target object mechanically coupled to the pair of thin planar members, wherein the displacement in a first direction parallel to the reference axis increases the separation distance between the pair of thin planar members and the displacement in a second direction opposite to the first direction decreases the separation distance between the pair of thin planar members. The physical variable related to the displacement is determined as a function of an electrical parameter varying as a function of the separation distance between the pair of thin planar members such as the electrical capacitance or resistance therebetween measured by a capacitance or ohm meter.

Abstract: Devices and methodology are provided for measuring mechanical strain in a structural member. The devices and methodology utilize a material which undergoes a change in phase when strained so that measurement of the phase change indicates strain. Preferably the phase change material is a transformation induced plasticity steel alloy. The elements may be configured as gauges secured to a structural member, but also the elements may perform as part of the structure. A plurality of elements may be organized into a monitoring system, either passive or active, for a complex structure.

Abstract: A field-based movement sensor adapted for measuring strain along a certain axis in an object on which the sensor is attached. The sensor includes a substrate having a working surface and formed with a pair of fingers projecting from a first direction, and a third finger projecting from a direction opposite the first direction, to a position between the pair of fingers. The pair of fingers and third finger extend generally perpendicular to the axis along which strain is to be measured, with the pair of fingers being moveable with respect to the third finger along the axis when the strain occurs. An electrically charged element for producing an electric field is disposed on the working surface of the third finger, and a pair of field-effect transistors (FETS) are each disposed on a working surface of a different one of the pair of fingers.

Abstract: The lifetime NF (number of cycles to failure) of a metallic structure such as a soldered joint or the like is determined by three simple, rapid tests. The first is to determine creep displacement rate vs. load (stress). Next, from the same data, the slope of the matrix creep displacement vs. load (stress) curve is determined. A third test is to obtain load (stress) relaxation over a short period of time from a load (stress) in the matrix creep displacement region. The matrix creep displacement per cycle (CPS) is then derived by plotting matrix creep displacement rate vs. time and integrating the area under this curve.

Abstract: The invention relates to an apparatus consisting of a device for generating a magnetic field mounted for movement relative to a product sitting in or moving through its field which is suspected of carrying at least one metal component which will cause the generator to move either toward or away therefrom because of either the attractive or repulsive forces, or both, caused by the presence of this metal or these metals. A load-responsive element in the form of a load cell is connected to the field generator so as to sense its movememnt if any and output a signal evidencing such movement. A detector is connected to receive the output signal from the load cell and use this information to initiate an appropriate response to the presence of the metal or metals causing the displacement of the generator.

Abstract: A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

Abstract: Changes in linear dimension of objects are determined by measuring strains caused in an electrical resistance strain gauge which is attached to an elongated element with a high modulus of elasticity provided on at least one end of an elongated body with a low modulus of elasticity extending in the direction of linear dimension of the object.

Abstract: A mechanically adjustable tunnelling junction includes two electrodes defining a gap supported on substrates. Spacers maintain the electrodes in spaced apart relation. At least one of substrates is mechanically deformable, whereby the application of an external force to the substrates decreases the gap to the range where tunnelling will occur.

Abstract: Early detection of cracks in structural members subject to stress is accomplished before cracks traverse the member by(a) affixing multiple liquid impermeable enclosures to the material to be monitored such that a crack forming in the monitored material will provide passage for liquid to enter the enclosures either through the monitored materials or by destroying the integrity of said liquid impermeable enclosures;(b) sealing a resistor having a known value onto each of the enclosures, each of the resistors having one lead capable of liquid contact within the enclosure, said lead electrically isolated from the material being monitored and/or a second wire in the enclosures;(c) forming a circuit connecting the multiple enclosures wherein the opposite resistor leads in each enclosure are connected by insulated wire to means for measuring resistance and/or conductance wherein each resistor alone or together with any combination of other resistors in said enclosures within the circuit provides a unique total resi

Abstract: A force and pressure transducer comprises a plate-like crystal. Two separate portions of the crystal are maintained in oscillation at separate frequencies by a circuit. The force to be measured, is applied by a seating to a part of the crystal edge such that compression in one of the oscillating portions causes the frequency of that oscillating portion to change substantially whereas the frequency of the other portion changes only minimally.In the past it has been difficult to manufacture crystals in which the frequency versus temperature response of each of the two oscillating portions was sufficiently well matched to permit the difference frequency between the portions to be used as the instrument output signal.This invention resides in the application of a second fixed force by a spring via a seating to a second part of the crystal edge in such a way as to influence the frequency of oscillation of this second portion.

Abstract: An electronic d.c. amplifier arrangement for use with a bridge network incorporating at least one sensing element, the supply to said bridge being effected via respective differential amplifiers, one of which is connected to compensate for the length of line between the arrangement and the bridge network, and the other effects automatic zero-compensation, while a further differential amplifier of adjustable gain provides an amplified output from said bridge network.

Abstract: A process and apparatus applicable to products which are or can be made electrically conductive for the purpose of measuring information encoded in them as a result of the manufacturing steps employed. Elemental mechanogalvanic potentials reflect a measure of the total information content of a product and are generated when the product serves as an electrode and where a second electrode with a rollable solid electrolyte in contact with the product rolls over it generating data related to the elemental constituents of the product. Mappings or numerical matrices whose elements are the mechanogalvanic potentials can be the basis of extensive important analysis by conventional mathematical procedures.

Abstract: A signal classifier system is disclosed that includes an on-line apparatus for monitoring various electrical signal inputs derived from vibration signals without data interruption, and providing an output from each of several levels of classifications. Classification is by a three-level classification algorithm. A first level of classification provides for the independent processing without structural or operational information of each signal input. The output of the first level is stored according to a strain gauge in a spatial file. The second level of classification provides a combination of the output of the spatial file with structural information (such as compressor structural information) and on-line operational information to provide an output indicative of event probabilities which are stored.

Abstract: A micromachined force sensor containing separate sensing and actuator structures. A member is suspended above the substrate so that it is movable along an axis in response to a force. The member includes a set of parallel sense fingers and a separate set of parallel force fingers. The sense fingers are positioned between fingers of two sense plates, to form a first differential capacitor, whose capacitance changes when the member moves in response to a force along the axis. The change in capacitance induces a sense signal on the member, which permits the measurement of the magnitude and duration of the force. The force fingers are positioned between fingers of two actuator plates, to form a second differential capacitor. The sense signal can be used to provide feedback to the second differential capacitor to generate different electrostatic forces between the force fingers and the two actuator plates, to offset the force applied along the preferred axis.