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 digital eddy current apparatus for sensing and analyzing metallurgical characteristics of an electrically conductive material. A square wave is supplied to a resonating circuit which includes a coil used as a sensing element for the conductive material. The resonating circuit produces a sinusoidal wave which is converted into a rectangular pulse which, when the resonating means is at resonance condition if superimposed upon the square wave pulse it would be positioned in the center of one-half of the square wave. The width of the rectangular pulse is a direct function of the amplitude of the sinusoidal wave and phase shift of the sinusoidal waveform is detected by movement of the rectangular pulse from the center position within the square wave. The width and position of the rectangular pulse is a direct function of the metallurgical characteristics of the conductive material.

Abstract: Magnetic cores of clamp-on type current measuring devices having a Hall-effect device for measurement of D.C. currents are provided with stabilizing coils which are periodically energized to substantially eliminate the characteristic hysteresis effect of the core material. A magnetic core of the type which is split to permit opening and subsequent clamping onto a conductor, has one section thereof provided with an air gap in which the Hall-effect device is positioned. A stabilizing coil is positioned on one section of the magnetic core and the coil and is periodically energized with a damped oscillatory current. This damped oscillatory current is at least applied immediately prior to the taking of any current measurement and is preferably applied periodically to maintain the stability of the magnetic core.

Abstract: A magnetic field sensing circuit using three windings on a magnetic sensor with one winding using a locally generated excitation voltage, a second winding providing an output induced by the excitation voltage and a third winding both providing external magnetic field sense signals and serving as a feedback winding. The induced excitation voltage is used to generate a signal indicative of the flux in the core for the ultimate purpose of logically switching the sense winding so as to rectify it and supply it back to the third winding as a feedback signal for counteracting the flux in the sensor due to the external field being sensed.

Abstract: An elongated generally U-shaped ferromagnetic yoke has a series of coils embedded in its leg portions at spaced positions along its length so that a magnet body can be moved along the length of the air gap of the yoke so that that it can be magnetized and measured for a magnetic characteristic. A conveyor and a sorting device are also included so that magnet bodies exceeding minimum standards can be selected automatically. Other functions, such as partial demagnetization, and complete demagnetization, can be accomplished by other coils, or permanent magnets, embedded in the yoke.

Abstract: An illustrative embodiment of the invention provides a method and apparatus for magnetic inspection of areas of interest in ferromagnetic material by means of both alternating and direct current induced magnetic fields. Moreover, the magnetic fields may be pulsed sequentially and/or simultaneously to detect defects deep within the area of interest.

Abstract: A transducer is utilized to convert the eccentricity of a turbine shaft into a sinusoidal electrical voltage signal having a given frequency, amplitude and a DC bias. This electrical signal is provided to a circuit which periodically measures the maximum and minimum peaks of the sinusoidal signal. The frequency at which the latter measurements occur is related to the frequency of the sinusoidal input signal. The maximum and minimum levels of magnitude are stored periodically as DC levels and subtracted from each other to determine the absolute value of eccentricity. In addition the stored minimum value is compared with the sinusoidal signal to reduce the DC bias of the sinusoidal signal to a point where the negative peaks thereof are at zero.

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.

Abstract: To test the flux of circular segmental permanent magnets for assembly in permanent magnet dynamo electric machines, typically electric motors, a gauge is made of soft iron having an inner segmentally circular soft iron core, on it a layer of non-magnetic material to simulate the air gap of the motor, space for the permanent magnet to be inserted, and a return soft iron yoke in magnetic circuit with the core. A measuring coil which is chorded is located on the gauge to sense the magnetic flux, and so placed on the core that it conforms, at least approximately, to the pitch angle of the armature winding of the dynamo electric machine with which the magnet is to be used.

Abstract: An orthogonal coil metal detector with nesting rectangular coils, each comprising a plurality of turns encapsulated in an insulating material and having a layer of electrical resistive material thereon. An encapsulating material in the gap between the coils bonding the coils together. A fixture for supporting the coils in spaced relations and providing for translation and rotation of one coil relative to the other for adjusting the coil position to a minimum coupling condition, and for holding the coils in the adjusted condition during curing.

Abstract: A high frequency pickoff is disclosed having two spaced inductors electrically connected in series and a capacitor connected in parallel with the inductors, thereby forming a parallel resonant circuit. A conducting member is mounted for motion in the space between the two inductors. A pair of transistors are mounted in push/pull configuration to alternately connect first one end and then the other of the resonant circuit to a source of electrical energy. The source disclosed is a current source for matching the high impedance of the parallel resonant circuit. When the electrical energy is switched at substantially the resonant frequency of the parallel circuit, differential motion of the conducting member relative to the inductors provides differential amplitude output at the frequency of resonance of electrically opposed ends of the resonant circuit.

Abstract: Apparatus for measuring, and indicating, the thickness of non-metallic coatings over a metallic surface, such as in sheathing of an electrical cable or similar structure, has a number of measuring heads, for example four, of electrical inductance type, spaced around the structure. A probe in each head has a profiled surface for presentation to the surface of the coating, the profile such as to offset any variation in inductance effects on the probe resulting from variation in diameter of the cable, without affecting the inductance effects of any variation in coating thickness. The measuring head is flexibly mounted and the signals from circuits associated with the probes are arranged to give visual indication of variation in coating thickness, and also any eccentricity. Particularly the indication can be a visual one representative of the cross section of the cable or the like.

Abstract: Apparatus for detecting the direction of a magnetic field includes a magnetoresistive device comprising an insulating substrate, first and second ferromagnetic metal film strips on the substrate for providing first and second main current conducting paths respectively perpendicular to each other, the ends of the strips being connected together to form an output terminal and having current input terminals connected to the opposed ends of the strips. A stationary bias magnet is disposed adjacent the magnetoresistive device for supplying a bias flux at a predetermined angle relative to a main current conducting path.In one application of this apparatus, the magnetic field is supplied from, for example, a magnet, such as a rotary magnet, thereby to apply, with the bias flux, a composite flux to the magnetoresistive device. An output signal is derived from the output terminal that is a function of the direction in which the magnetic field is supplied.

Abstract: A measuring head using the electrical inductive principle has at least one probe with a surface for presentation to a surface of a non-metallic coating over an arcuate metallic surface, the thickness of which coating is to be measured. To offset the varying inductive effects caused by variations in diameter of the article being measured, the surface of the probe is profiled--having a Vee shaped profile. The profile is such that articles, such as cables, of smaller diameter enter the Vee shaped profile deeper than larger diameter articles. By this means only variations in inductive effect resulting from variations in coating thickness occur.

Abstract: A dual biased magnetic transducer capable of sensing magnetically recorded data on a magnetic medium without any relative velocity between the transducer and the medium. The transducer includes a third DC bias field for aiding the DC field created by the data on the medium for substantially shifting the level in the AC carrier, thereby producing a computer compatible intelligible signal.

Abstract: A probe for sensing the strength of the magnetic field that surrounds a current-carrying conductor has a square-loop magnetic material wrapped about a conductor which is placed in the magnetic field to be sensed. An alternating signal is applied to the conductor, of sufficient intensity to cause successive reversals of the polarity of the magnetic material. A sense winding around the magnetic material issues a switch signal every time the magnetic material reverses polarity. The switch signal is used to sample the alternating drive signal current in order to store the amplitude of the drive signal at the instant at which the magnetic material reverses polarity. The sampled signal amplitude is averaged over a period of time, and the resultant amplitude is a linear function of the strength of the magnetic field. A second conductor, magnetic material and sense winding are arranged in a position remote from the magnetic field in order to sense the effect of the Earth's magnetic field.

Abstract: One or more dimensions of each of a series of similar manufactured elements, which are formed of magnetizable materials such as iron, steel, nickel or the like may be quickly checked for conformity to a predetermined value by momentarily positioning each successive element against an electromagnetic sensing device. The sensing device has a winding establishing a magnetic flux path through a core which is formed with one or more gaps in the magnetic circuit that are located to be spanned by a wrongly dimensioned or wrongly oriented one of the manufactured elements. Spanning of a flux gap of the core by a wrongly dimensioned or misoriented element changes the self-inductance value of the winding, and circuit means are provided for detecting such change in order to indicate the presence of a disconforming element or to actuate mechanism for rejecting or correcting the element.

Abstract: When a negative resistance is connected in parallel to a parallel resonance circuit composed of coil and condenser for detecting flaws and other defects of a travelling metal material, the detecting system is capable of improving sensitivity for detecting said flaws and lowering the required degree of amplification of the following amplifier, consequently reducing influence depending upon unbalance of a bridge circuit. At the same time, the simplifying of the power source of said system may be easily realized.

Abstract: An apparatus and method for measuring stresses or forces by measurement of variations of the magnetic properties of ferromagnetic substances under stress conditions. This is carried out by providing a ring of ferromagnetic material between two parallel faces on or between which the stresses are exerted, the ring defining a magnetic circuit, providing an electric coil within and around the ring, passing a current through the coil and measuring changes in the properties of the current to measure variations in the magnetic properties of the ring.

Abstract: Apparatus for measuring displacements of core components of a liquid metal fast breeder reactor by means of an eddy current probe. The active portion of the probe is located within a dry thimble which is supported on a stationary portion of the reactor core support structure. Split rings of metal, having a resistivity significantly different than sodium, are fixedly mounted on the core component to be monitored. The split rings are slidably positioned around, concentric with the probe and symmetrically situated along the axis of the probe so that motion of the ring along the axis of the probe produces a proportional change in the probes electrical output.