Abstract: A magnetic inspection apparatus includes a magnetizer which generates a magnetic field in an object to be inspected, the object running in a predetermined direction, the magnetizer including a pair of magnetic poles provided in facing relation to the object, the pair of magnetic poles being arranged in the predetermined direction; a plurality of magnetic sensors arranged at small intervals in a widthwise direction of the object perpendicular to the predetermined direction, for detecting a leakage magnetic flux due to a defect of the object at locations in the widthwise direction, each magnetic sensor having sides which face the magnetic poles; a plurality of subtraction circuits, each calculating a difference signal between output signals from those ones of the magnetic sensors which are separated by a predetermined distance; a plurality of absolute value circuits, each calculating an absolute value of each difference signal output from each subtraction circuit; and an arithmetic operation circuit which evalu

Abstract: In a magnetic inspection method and apparatus, a magnetizer (4) is provided such that a pair of magnetic poles (4a, 4b) face an object (10) to be inspected. A magnetic field is generated by the magnetizer (4) in the object (10). A magnetic sensor (7a) is situated at a substantially middle point of a line connecting the magnetic poles (4a, 4b) or a line parallel to this connecting line. Shield bodies (22a, 22b, 23a, 23b) with a low coercive force are arranged on those sides of the magnetic sensor (10) which face the magnetic poles. The magnetic sensor (7a) detects a leakage magnetic flux due to an internal or surface defect of the object (10). In addition, the distance (2A) between the shield bodies (22a, 22b) is 2.2 times or more, and 2.8 times or less, the distance (L) between the magnetic sensor (7a) and the object (10).

Abstract: A magnetism detecting apparatus of this invention includes a magnetic sensor (11) constituted by a ferromagnetic core (12) and a detection coil (13) wound around the core (12), a parallel resonance circuit (15) constituted by the detection coil (13) of the magnetic sensor (11) and a capacitance element (14) connected in parallel with the detection coil (13), an oscillation circuit (18), which is constituted by an amplifier (16) to which the parallel resonance circuit (15) and a resistor (17) are connected as a feedback circuit, and the parallel resonance circuit (15), and excites the core (12) to a saturation region by using an oscillation current, and a waveform change detecting circuit (22, 24) for detecting a change in waveform of an output signal from the oscillation circuit (18).

Abstract: In a magnetic inspection apparatus for a thin steel strip of the invention, a pole-to-pole distance of a magnetizer, which is housed in a hollow roller contacting a traveling thin steel strip to oppose the thin steel strip, is set between twice and eight times a distance between magnetic poles and the thin steel strip. A position of a magnetic sensor in the travel direction of the thin steel strip is shifted from the central position of the magnetic poles to a travel direction side by a small distance. In this invention, a pair of hollow rollers are provided to sandwich upper and lower surfaces of a traveling thin steel strip, and magnetic sensors are respectively housed in the hollow rollers. As a result, a position of a defect in the direction of the thickness of the thin steel strip, and a defect size can be accurately detected.

Abstract: Karaoke is provided more easily and flexibly by recording video signals from multiple video sources on a disk; selecting one of those sources as desired; and reproducing the signals from that source along with either the output of a video camera or graphics data. The graphics data is recorded on the disk with the video source signals in multiplexed fashion, along with selection signals. When the multiplexed signals are demultiplexed, chroma-key composite circuitry effects desired superimposition of a video camera output on the source video signals.

Abstract: A current measuring method in which a magnetic sensor is a torodial core having a conductor for carrying a current to be measured passing through the hollow portion of the toroid. A coil on the core is excited with an AC voltage such that the positive and negative voltages induced in the coil are equal in amplitude when the conductor is not carrying current. Current in the conductor generates a change in magnetic flux which change is measured by detecting the algebraic sum of the amplitudes of the positive and negative voltages. Simultaneously, the amplifier output is applied to the input side of the AC voltage or a second coil disposed in the magnetic sensor so as to establish a magnetic equilibrium. Current measuring apparatus according to this invention include two types of apparatus composed of hardware to which the above-mentioned current measuring method is applied.

Abstract: An apparatus for detecting a surface flaw of each pipe constituting a pipeline, including a pig capable of travelling along pipeline and being provided with the following elements: a cylindrical primary coil coaxial with the pipe, the density of a magnetic flux of an AC magnetic field of the primary coil varying in response to an inner surface flaw of the pipe; a plurality of cylindrical secondary coils arranged at prescribed intervals in the circumferential direction of the pipe between a peripheral surface of the primary coil and a confronting peripheral surface of the pipe, each secondary coil having an axis parallel to the axis of the primary coil, and producing an AC voltage proportional to the density of a component parallel to the axis of each secondary coil, of the magnetic flux of the AC magnetic field of the primary coil; and a signal processing circuit for processing the AC voltage signals from the secondary coils to detect the presence and the depth of a surface flaw of the pipe.

Abstract: Eddy current distance measuring apparatus includes a multiplier connected to one secondary coil of a pair of secondary coils in an eddy current sensor. The secondary coil outputs are inputted to a differential amplifier, and the resulting difference is adjusted to be zero when an object the distance to which is to be measured is not present. Thereafter, the sensor is located within measuring distance of, e.g., a steel plate, and the output of the differential amplifier is combined by an amplifier circuit with an oscillator output supplying a current to the primary coil of the sensor. An eddy current distance signal output is thus obtained.

Abstract: An apparatus for measuring the level of molten metal in the oscillating mold of a continuous casting machine in operation by an eddy-current type distance measuring device. The oscillation signal component due to the oscillation of the mold is extracted from the output signal of the distance measuring device and the detection sensitivity of the distance measuring device is compensated and controlled so as to maintain the amplitude value of the oscillation signal component at a constant value thereby linearizing the molten metal surface level versus output characteristic.

Abstract: The distance between the tip of a probe and a high-temperature object of measurement is continuously and accurately measured by arranging the probe comprising a primary coil and a pair of secondary coils substantially vertically to the object of measurement; inducing an AC voltage (e.sub.1) and an AC voltage (e.sub.2) respectively in the pair of secondary coils by means of an AC magnetic field of the primary coil excited by an output voltage (e.sub.out) of a positive feedback amplifier; generating an eddy current in the object of measurement by means of the AC magnetic field of the primary coil to generate another AC magnetic field in the direction opposite to that of the AC magnetic field of the primary coil; impressing an equal DC voltage onto each of the pair of secondary coils to detect respectively a DC voltage (E.sub.1) and a DC voltage (E.sub.2) of the pair of secondary coils; calculating an error voltage (e.sub.

Abstract: A method for continuously measuring the steepness of a defective flatness of a metal strip during rolling, which comprises: detecting a variation in the relative distance between a metal strip during rolling and a distance-detecting means arranged adjacent to the surface of said metal strip, during the travel thereof between two support rolls arranged at a prescribed spacing, by means of said distance-detecting means, as a vibration including a vibration corresponding to a defective flatness produced in said metal strip; calculating the natural vibration frequency of said metal strip during the travel thereof between said two support rolls, from the detected value of the tension applied to said metal strip during the travel thereof between said two support rolls, the specific weight of said metal strip, and the distance between said two support rolls; cutting off the frequency components, which are below said calculated value of the frequency of said metal strip, from said detected value of the vibration of s

Abstract: An apparatus first magnitizes a base metal with an alternating flux to cross the welded seam of the base metal and the resulting leakage flux from the welded seam is detected by at least one flux search element to generate an AC signal. The fundamental harmonic component corresponding to the magnetizing signal used for the alternating magnetization is eliminated from the AC signal and the resulting signal voltage is sampled at a fixed period corresponding to the period of the magnetizing signal, thus detecting the center position of the welded seam from the result of the sampling.

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: There is disclosed a molten metal level monitoring and controlling apparatus for continuous casting machines which employs an eddy-current type distance measuring device for measuring the level of the molten metal in the mold of a continuous casting machine. The eddy-current type distance measuring device generates a molten metal level signal by detecting in a noncontact manner the distance between its detecting mechanism fixedly mounted in place just above the surface of the molten metal and the molten metal level.

Abstract: An apparatus for measuring the temperature of a metallic body in a non-contact maner includes an electronic circuitry for measuring a change in the impedance of a detecting coil arranged oppposite to the metallic body. The electronic circuitry comprises an operational amplifier, a negative feedback circuit with adjustable feedback factor, a positive feedback circuit, an oscillator, a phase shifter circuit and a synchronous detection circuit. The change in the impedance of the detecting coil is caused by the effect of eddy current produced by the application of alternating field to the metallic body, and this impedance change is dependent on change in the temperature of the metallic body. By adjusting the negative feedback factor .beta..sub.N of the negative feedback circuit and the phase angle .theta.

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: Apparatus for non-contact measurement of the distance between a detecting coil and a metallic body mounted in confronting relation thereto comprising a differential amplifier to one terminal of which is connected a reference oscillator and to the other terminal of which is connected a feedback circuit. The feedback circuit incorporates the detecting coil and the amplified differential output signal between the AC signals applied to the differential amplifier and the signal supplied to the differential amplifier resulting from the impedance of the detecting coil corresponding to the distance between the detecting coil and the metallic body are thus a measure of the distance.

Abstract: The measuring apparatus comprises an electromagnetic induction type non-contacting distance measuring device including a detection coil disposed near the edge of a running metal strip, a filter for deriving out the high frequency component and the low frequency component of the output of the detection coil, means responsive to the high frequency component for determining the contour of the wavy edge of the strip and means responsive to the low frequency component for adjusting the lateral position of the detection coil with respect to the edge of the metal strip.

Abstract: In measuring the distance between a measuring sensor and a metallic body, the sensor is comprised by a resonance circuit including a capacitor and a coil, and the sensor is connected to the input of a Q multiplier circuit which is impressed with an AC signal having a predetermined frequency. The non-linear distance-inductance characteristic of the coil is compensated for by adjusting the selectivity of the resonance circuit so that the amplifier included in the Q multiplier circuit produces a linear output. Such compensation is performed by adjusting the gain and/or the amount of positive feedback of the Q multiplier circuit.

Abstract: The detector comprises a reference AC signal generator with one terminal grounded, a feedback amplifier having one input connected to receive the reference AC signal; a feedback network coupled to the output of the feedback amplifier, the other input of the feedback amplifier, and the grounded terminal so as to supply a feedback voltage between the grounded terminal and the other input of the feedback amplifier; and a detector for detecting the output of the feedback amplifier. The feedback network includes two serially connected detection coils spaced in the direction of movement of a metallic member to be detected to vary their impedances in accordance with the variation in the electric or magnetic characteristic of the metallic member.