Abstract: Apparatus for detecting ferromagnetic material such as is present in an explosive cartridge being loaded into a borehole, e.g., according to the method described in U.S. Pat. No. 3,986,430, which includes an inductance coil connected in series with a resistor, separately rectifies and amplifies the AC voltages across the coil and resistor and connects them in series opposition. The value of the balancing resistance is adjusted so that the two rectified voltages are equal and opposite when no ferromagnetic material is present. When the unbalance voltage exceeds a threshold value, a signalling device is actuated.

Abstract: A self inverting gauging system for such parameters as capacitively sensed distance or inductively sensed resistivity in which the sensor provides an output inversely varying with the dimension of interest. The gauge typically includes a dual slope integrator responsive to a reference value on the up integration and to the sensor output on the down integration. The interval of the down integration necessary to reset the integrator to the original value varies directly, rather than inversely, with the dimension of interest and is typically provided as the digital output indication of a counter. In the application to resistivity gauging, the up integration reference signal is preferably provided by the output of a thickness gauge such that the ultimate counter display represents element resistivity compensated for thickness.

Abstract: A displacement transducer includes a non-magnetic non-conductive former mounting helical bifilar windings. Slidable within the former is a conductive non-magnetic member the position of which is varied for the purpose of measuring displacement. The windings in use form the frequency determining component of an oscillator the frequency of which is a measure of the setting of the member.

Abstract: A control circuit for measuring the distance between a workpiece and an electrode which is formed as inductance and is part of a resonant circuit as a frequency-determining element whereby the frequency variations of the resonant circuit for producing voltage and/or current changes which are proportional to a distance are connected to a measuring circuit and includes at least two partial inductances in the resonant circuit with one inductance being represented by the electrode and the other being a stationary resonant circuit arranged at a distance from the electrode and in the immediate influence sphere of the workpiece.

Abstract: A harvester of the type comprising a pick-up mechanism operative to gather harvested material from the ground and to supply the same to a conveying structure within the harvester is further provided with a metal detector located within the harvester between the pick-up mechanism and conveying structure. The metal detector comprises a non-conductive shield structure which is disposed adjacent the path of movement of material passing from the pick-up mechanism to the conveying structure and arranged to provide a surface over which said material passes, and sensor means mounted within the shield structure and operative to produce a field which penetrates said surface and extends transversely across the path of movement of material being supplied by the pick-up mechanism to the conveying structure.

Abstract: An apparatus for measuring dynamic magnetostriction subjects a test sample to a spatially uniform, sinusoidal magnetic field of constant peak amplitude. Accelerometers mounted on the test sample produce a first electrical signal representative of the acceleration of the test sample due to the induced magnetic field. The first electrical signal is integrated twice producing a signal representative of the displacement of the test sample due to the induced magnetic field. This signal is representative of the magnetostrictive movement of the test sample.

Abstract: An instrument for computing resistivity based upon measurements of thickness and conductance. A conductance transducer is a solenoid in an annular ferrite cup connected to a tank circuit for an eddy current measurement of conductance. Within the center of the annular ferrite cup concentric acoustic wave sending and receiving channels are disposed for making an acoustic pressure wave measurement which is used for a thickness measurement using two gauge heads, spaced on opposite sides of an article to be measured. Each gauge head contains identical conductance and thickness transducers. The thickness measurement is divided by the conductance measurement to derive resistivity.

Abstract: An electronic vehicle detection installation of the type using a detector loop laid in the roadway senses changes in the inductive time constant of the loop. The changes are sensed by determining the phase difference between a voltage impressed on the loop and the loop current or by making the time constant the predominant frequency determining parameter of an astable oscillator. A digital processing circuit is provided to sense vehicle-indicative changes in the oscillator frequency. Clock pulses are counted over a selected number of oscillator cycles, the scan cycle, and the number counted over one scan cycle is compared with that stored from the preceding cycle. Provision is made to adjust the stored value for ambient changes and for the continued presence of a vehicle after a selected presence period.

Abstract: A developer level sensor installed on the sidewall of a developer container in a developing apparatus consists of an oscillator circuit with multiple coils, the mutual inductance of which is adjusted by a moveable electric conductor. The lower limit level of developer sensed may be adjusted by the positioning of a control plate.

Abstract: An apparatus for non-contact measurement of the distance or gap between a detection coil and a metallic body arranged in an opposing relation with the detection coil, includes a differential amplifier having one input terminal connected to a reference oscillator and the other input terminal connected to a feedback circuit. The detection coil comprises a cylindrical coil and a plurality of magnetic members in rod form are arranged inside its inner bore along the direction of the coil axis and adjacent to the coil inner wall. The plurality of magnetic members comprise a combination of those having positive temperature characteristic and others having negative temperature characteristic so that a change with temperature of the permeability of the magnetic members as a whole is practically reduced to zero.

Abstract: A device for detecting metallic objects in a container having a substantial quantity of non-metals therein including a frame with metal detecting means mounted on the frame such that the metal detecting means defines a plane of detection. This plane of detection has a length defined as "L" which is substantially equal to the length of the detecting means, and the plane has a width equal to distance "R". A container means of non-metallic material is provided for holding a quantity of non-metal which might contain metallic objects therein. The container has a length less than or equal to L and a diameter less than 2R. Rotating support means for positioning the container in the plane of detection is adapted to rotate the container about an axis of rotation parallel to length L and less than distance R from said detecting means. Alarm means for signalling the presence of a metallic object passing through the plane of detection during rotation of the support means is also provided.

Abstract: Bearing assemblies with inner and outer races and rolling elements therebetween incorporate local sensing means for producing a signal indicative of the movement of one of the races relative to the other. The sensing means is mounted in close proximity to one of the races and is usually directly secured to the race intended to be stationary. The sensing means can be mounted laterally of the bearing races or radially inside or outside of the bearing races.The sensing means may employ an inductive or capacitive sensor and oscillatory means and a body or component, such as a disc, carried by the movable race creates an influence detected by the sensing means to provide the signal. In other constructions the sensing means detects changes in electromagnetic radiation or fluid pressure created by the component or body carried by the movable race.

Abstract: Disclosed is a device for measuring the concentration of toner in a developer mixture composed of toner and a ferromagnetic carrier material, e.g., in an electro-photographic developing device. The device comprises a measuring oscillator which comprises an inductance-including component comprising at least one coil wherein the conductor paths of the coil lie substantially in one plane; means for passing at least a portion of the developer mixture into the zone of the inductance; and means for evaluating changes in the frequency of the oscillator resulting from changes in the developer mixture composition passing over the zone of inductance. Also disclosed is an electro-photographic copying apparatus embodying the foregoing device.

Abstract: A method and apparatus for delivering energy to an oscillatory system in a signal transmitter to maintain the system in a state of oscillation. A component of the oscillatory system that affects the oscillation frequency is influenced by the magnitude of a measured condition which is to be transmitted by the signal transmitter. The oscillatory state of the system is sensed through a signal path, and energy is delivered to the system through substantially the same signal path, said energy being delivered in the form of pulses at time intervals longer than a whole period of oscillation of the system to maintain the system in a state of oscillation.

Abstract: A guidance system suitable for use in burying cable uses a previously buried signal-emitting cable to produce a signal along the cable path. A vehicle mounted plow used to plow a second path has a receiver which analyzes signal from the buried cable and determines from it both the lateral direction and the extent of vehicle movement in order to maintain a predetermined lateral spacing of the two paths.

Abstract: The apparatus comprises a parallel coil and a capacitance, the coil having an air gap in which an unknown specimen is inserted, a source of alternating voltage applied to the coil-capacitance combination, scanning means for automatically varying the value of the capacitance in steps, thus varying the phase of the voltage across the coil, means for digitizing the phase of the voltage corresponding to each capacitance value, a memory in which those digitized phase values are stored, a reference memory containing digitized phase values for known specimens, and means for comparing the digitized phase values of the unknown specimen with those of known specimens. A digital tolerance control circuit is also provided which accommodates deviations between the reference and the known phase values, up to predetermined amounts, and means are provided for displaying the generic name or grade of the stored phase values which match the phase values of the unknown specimen.

Abstract: A powdered toner mixture comprising a non-magnetic toner component and a ferromagnetic carrier component is caused to flow downwardly through a vertical conduit by gravity. An electromagnetic coil is wound around the conduit and energized with an alternating electric signal. An electrically conductive and magnetic mass is disposed inside the conduit. The permeability of the toner mixture decreases as the toner density, or the ratio of the toner component to the carrier component, increases. The lower the permeability of the toner mixture, the greater the proportion of magnetic flux passing through the mass. The flux passing through the mass induces eddy currents therein which, in combination with hysterisis and skin effect losses, dissipate a portion of the electric signal. The amount of power dissipation is a function of the relative proportion of flux through the mass and thereby the toner density and, when measured, provides a measure of the toner density.

Abstract: A plurality of eddy-current generators are angularly grouped about an axis within an inspection tool or probe. Each eddy-current generator presents a circumferentially extending test segment. Collectively, the test segments form a discontinuous test gap which extends circumferentially about the probe. In some embodiments, adapted for inspecting from the inside of tubing or fastener holes, the test gap is at the outer periphery of a probe. In other embodiments, adapted for inspecting from the outer surface portions of tubing, rods, etc., the test gap region extends around the inside of a central passageway formed through a support body. The eddy-current generators are supported for limited radial movement, enabling the tool or probe to adapt to differences in shape and dimension of the material being inspected.

Abstract: A metal detector is disclosed. The detector comprises oscillator circuit means comprising a first transistor, a second transistor, adjustable resistor means coupled to the emitter of the first transistor, and inductor means arranged to control the conductive state of the second transistor. The oscillator circuit means is arranged to generate an electromagnetic field and the second transistor is arranged to provide an output signal in response to and corresponding to any disturbance of the electromagnetic field caused by the presence of a metal article in the electromagnetic field.

Abstract: Deterioration of a dry developing substance causes toner particles to be so strongly adhered to carrier particles that they cannot be readily separated therefrom. The present apparatus comprises means for applying a predetermined electrostatic or air suction force to the developer to readily remove toner therefrom except for spent toner particles strongly adhered to the carrier particles. The toner density, or the ratio of toner to carrier particles, is then measured electromagnetically or optically and compared to a reference value. The developer deterioration determines what proportion of toner will be removed from the developer by said force and thereby the subsequently sensed toner density. The higher the sensed toner density, the greater the degree of deterioration.

Abstract: A device for determining the blood sedimentation rate in a substantially vertical test tube, where the electrical or magnetic property of a given volume of liquid, which is changed by the settling of the erythrocytes in the test tube is measured as a function of time, by means of an oscillator with an output circuit which is completed via the column of liquid to be measured and by means of a measured-value pickup, having an output signal of which a pulse sequence of a definite frequency can be fed to a pulse counter with an indicating device.A coil-capacitor resonant circuit is coupled inductively with its coil or capacitively with its capacitor to liquid at a definite height in the test tube. An additional coil inductively coupled to the resonant-circuit coil serves as the measuring pickup. A retuning circuit is provided for the retuning of the resonance of the tuned L-C circuit which is detuned by the lowering of the boundary layer between the erythrocyte column and the plasma in the test tube.

Abstract: In detecting the presence or absence of a developing agent or determining the residual amount thereof, at least one coil is arranged outside a developing agent container, so that a change in magnetic permeability caused by the presence or absence of a developing agent within the container or a change in the amount thereof can be detected as a change in the inductance of the coil.

Abstract: A pair of similar oscillators are coupled to each other such that when their natural resonant frequencies are close together they lock in and operate as synchronized oscillators over a predetermined range which can be selected by control of circuit parameters. Within the range where the oscillators are locked to be equal in frequency the phase angle between the frequency generated in each oscillator can be used as a measure of the influence on the resonant frequency of one oscillator relative to the other and where this influence is due to the parameters of an external test piece or the like influencing one oscillator, the measurement of phase angle is a measurement of a characteristic or parameter of the test piece.

Abstract: A flux-sensitive magnetic head employs, at its back part, a structure having a thin single domain magnetic film coated thereon. A coil wraps around the coated structure, and a direct current is passed through the coil, thereby to apply a hard axis magnetic bias to the film. Signal flux appearing at the head front gap asserts a magnetic force along the hard axis of the film. Contrary to what would be expected, the signal flux causes the inductance of the coil to vary. Such inductance variation may be conveniently detected by (1) connecting the variable inductor into a tank circuit, (2) applying a high frequency ac ripple to the "hard axis" dc bias, and (3) measuring the "hard axis" detuning experienced by the tank circuit.

Abstract: In a magnetic head of the type having a thin film magnetically-coated electrically-conductive wire bridging the windowed back section of the head, excitation currents are applied to the wire within the windowed head section.

Abstract: A digital device for detecting a metal object in the field of influence of a detector loop controlled by an oscillator which device creates a series of counting intervals and counts pulses during the intervals. The magnitude of the count during an interval is then indicative of metal detected by the loop. The count of a prior counting interval is stored and compared with the count of the next interval to determine whether or not there has been a detection. In this type of device there is provided an improvement wherein the magnitude of the counts stored during an interval is used to change the length of subsequent counting intervals. This maintains a generally high count magnitude for the counting interval to improve the sensitivity of the detecting device.

Abstract: Metal detector of the type having a tuned sensing loop which undergoes a shift in resonance and Q when brought into proximity to metal objects. In the absence of metal objects, the detector operates in a closed loop mode in which negative feedback is utilized to offset errors and maintain the excitation signal at an optimum frequency. Upon detection of a metal object, the system switches to an open loop mode in which the excitation signal remains at the optimum frequency and the output signal varies in accordance with the proximity of the object.

Abstract: A method of, and apparatus for, checking coins, wherein the coin to be checked is moved through a constantly regulated alternating-current field of a measuring coil. The influence of the coin upon the alternating-current field produces a regulation magnitude formed from the difference between a reference voltage and the rectified oscillator-measuring voltage. The regulation magnitude readjusts, by means of the oscillator circuit, the oscillator-measuring voltage at the measuring coil to a constant value. During coin checking the regulation magnitude is employed as the coin checking criterion in a manner such that it is possible to determine by means of an evaluation circuit whether this regulation magnitude has reached a value falling within an upper and lower boundary.

Abstract: A device for detecting phase transformations in a magnet material is disclosed. A sample is placed in a coil coupled to a harmonic oscillator and subjected to heat radiation means for simulating predetermined heating and cooling rates which result in phase transformations within the material being tested. The phase transformations are a function of changes in magnetic permeability which vary with temperature changes.

Abstract: An improvement in a digital device for detecting a metal object in the field of influence of an oscillator controlling loop, which digital device includes counter means for counting pulses during a counting interval, with the magnitude of the pulse count during the interval being indicative of the metal detected by the loop. The improvement includes means for creating a group of binary logic signals indicative of the difference between the pulse count and a selected reference count, these signals are allocated from a least significant to a more significant binary number, and reading means for reading the logic of at least some of the binary logic signals, which reading device includes means for indicating a detection when the signal being read has a selected binary logic pattern.

Abstract: A variable inductor having a U-shaped magnetic core with a short-circuiting plate providing a short-circuiting ring for both legs of the core movable along the core legs in response to a displacement to be measured is connected in an electronic circuit to generate oscillation of a frequency that is either directly or inversely proportional to the displacement. For the inversely proportional case, the variable inductance component can be combined with an integrator function and connected to an operational amplifier, for generation of the output frequency with a small number of electrical components. The thickness and spacing of the core legs are varied along their length to produce a highly linear inductive transducer characteristic. The core legs are bent in a circle when it is desired to measure an angular displacement.

Abstract: A linear oscillator circuit has a resonant circuit which develops an oscillating voltage V.sub.R having an amplitude proportional to a distance between a conducting body and the resonant circuit located within a probe. A control power drive circuit coupled to the output of the resonant circuit switches a current through the resonant circuit during each period of oscillation of the voltage V.sub.R. A reference current source is coupled to the control power drive circuit for drawing a current through the control power drive circuit and the resonant circuit. The magnitude of the current is equal to the magnitude of an independently established reference current. A detector circuit responsive to the value of the amplitude of oscillation may be provided to indicate the distance of the conductive body from the resonant circuit-containing probe.

Abstract: A method of, and apparatus for, monitoring the alignment of a pass defined between cooperating rolls in a mill stand during rolling bar, rod or section stock. Measurement is effected through eddy current sensors which are mounted in close proximity to the ends of the rolls and provide an output indicative of the amount by which they are spaced from the roll surface. In some instances other parameters e.g. roll wear, are also measured by similar eddy current sensors appropriately located in close proximity to the roll surfaces.

Abstract: A direct current proximity detector having a first terminal directly connected, to a terminal of a supply source and second and third terminals connected to the other terminal of the supply source through a load, an oscillator associated with a detector of its state of oscillation, a voltage stabilizer and a static switching device. The switching device comprises first and second transistors, the conducting state of the respective transistors depending upon the state of a corresponding output of an inverter unit which is controlled by the detector. The two transistors are connected to the first terminal through a Zener diode, second and third terminals being interconnected by means of two serially connected diodes of opposed polarities the common point of which supplies the voltage stabilizer.