Abstract: An improved electronic proximity sensor and crack detector that is primarily responsive to the induced resistance in a coil; including an LC resonating circuit that utilizes constant current and a DC power source. By sensing changes in the induced resistance, the invention detects various conditions of parts present and probe fault and can detect a crack in a rotating metal object that is in proximity with the probe. This is accomplished by sensing changes in the induced resistance that occur at the same frequency at which the metal object is rotating.

Abstract: Disclosed is an inductance detector for detecting boundaries between and characteristics of at least two adjoining substances having different characteristics, such as impedance, wherein a coil assembly, which is energized by an alternating current, is electrically coupled to a detector for detecting at least changes in impedance of the coil assembly caused by the boundary proceeding into and through the coil assembly.

Abstract: The invention relates to a process and to devices for the inspection of the surface of a member by means of an eddy current probe. By scanning the member means of the transducer following a given path, the sampled values of the signal supplied by the transducer are recorded for clearly defined positions of the transducer. By restoring the signals, it is possible to simulate a displacement of the transducer along a different path and/or simulate the displacement of a larger size or different type of transducer. The process may be used in steam generators in nuclear reactors and to the examination of irradiated fuel rods in these reactors.

Abstract: An inductive displacement transducer is described in which the magnitude of the phase difference between A.C. current and voltage in a coil is dependent upon the axial displacement of a monitored object. The phase difference depends upon the axial position relative to the coil of a short-circuit turn which moves with the monitored object. A magnetic flux concentrator, which may be combined with the short circuit turn, enhances the flux linkage between the short-circuit turn and the coil. In order to sense the height of a vehicle suspension strut, the coil is mounted on a plastics dirt shield, the short-circuit turn is provided by a sleeve plated with an electrically conductive metal and secured to the strut cylinder. Various circuits are described for monitoring the height signals produced by the different suspension struts of a vehicle.

Abstract: A proximity sensor for indicating the spatial proximity of a ferrous object omprising a magnetic reluctance bridge formed from a plurality of high and low permeability sections and with a ring core flux gate magnetometer disposed therebetween to form the center reluctance path of the bridge in order to sense flux when the bridge is unbalanced, a dc magnetic field generator disposed along a line of symmetry for the bridge for providing magnetic flux in the bridge, wherein a ferrous object disposed adjacent one of the low permeability sections will unbalance the bridge and cause flux to be detected by the flux gate magnetometer, and further including circuitry for generating a triggering signal when flux is detected by the magnetometer.

Abstract: The invention relates to the measurement of the ovalization of a ferromagnetic pipe.An electromagnetic pickup is moved in a circular path around the pipe, the pickup transmitting signals influenced by the radial distance between the pickup and the pipe. These signals are compared with signals from previous measurements made on a similar pipe to obtain indications of the radial distance between the pickup and the pipe so as to be able to deduce the transverse configuration of the pipe. The pickup is supplied with ac at a frequency of about 700 Hz and the signals from the pickup are compared with previously obtained signals both as to amplitude and phase.The pickup is mounted on a circular slide movable along a circular track supported on a U-shaped collar which is fixed to the pipe.

Abstract: An analog signal produced in response to eddy current probing of a test part is digitized by an analog-to-digital processor and then entered into a microprocessor-based computer.

Abstract: A detection type device that includes an arrangement for detecting the energy absorbed by a resistive effect element in proximity to the inductor of a resonant circuit. The resonant circuit uses a direct current source to alternatively charge it and then let it ring through a switch connected between the direct current source and the resonant circuit. Two different parameters of the same oscillating signal generated by the resonant circuit are detected and compared. The difference is the result of a ratio of these parameters that accurately reflects the energy absorbed by the resistive effect element. This difference is used for measurement and control purposes.

Abstract: A coin testing apparatus (10) comprises a coin passageway, a coin track (13) along which coins pass on their edges through the coin passageway and an inductor (16) adjacent the coin passageway. The inductor is connected in an oscillating circuit (40) so that the inductor (16) produces an oscillating magnetic field in the coin passageway. The frequency of the oscillating circuit is measured using a counter (41). A number representative of the idle frequency is stored in register (44). When a coin passes the inductor (16), the apparatus (10) detects whether the resulting frequency shift corresponds to the shift for an acceptable coin by comparing the difference between the number stored in register (44) and the number stored in counter (41) with a number previously stored in memory (48). The inductor (16) is oblong and has its major axis perpendicular to the track so that the arrangement is sensitive to variations in diameter over a large range of diameters.

Abstract: An apparatus for checking the geometrical features of mechanical pieces, including a feeler adapted to contact the macrogeometric profile of the piece to be checked, a transducer coupled to the feeler for providing a reference signal and a non-contacting sensing device including a reactive type transducer for providing a signal responsive to the microgeometry of the piece. A parameter indicative of the roughness of the piece may be obtained by processing the signals provided by the transducer coupler to the feeler and by the other transducer.

Abstract: An apparatus for characterizing a surface anomaly in an electrically conductive sample includes an oscillator with an amplifier for supplying gain to the oscillator, a feedback loop linking the input and output of the amplifier, a two port ferromagnetic resonator connected within the loop to modulate the level and frequency of oscillation of the oscillator in response to eddy currents induced in the surface of the sample by the resonator, a variable attenuator connected within the loop to adjust the power level of the oscillator, and an adjustable phase shifter connected within the loop for changing the total phase shift of the loop. A sensing circuit is operably connected to the output of the amplifier to monitor the resonance parameters of the oscillator.

Abstract: An electric sensing circuit, typically a metal detector includes a bridge including inductors. The out of balance condition of the bridge is stored on a capacitor and a balancing signal is fed to balance the bridge in dependence upon the stored value of the charge. The stored value of the charge is only updated in response to relatively slow changes in the out of balance condition of the bridge. Relatively rapid changes in the out of balance condition are used to provide an output signal for alarm or measuring purposes, and the arrangement is thereby so arranged that the balancing signal does not attempt to automatically balance out the output signal giving the alarm or measurement.

Abstract: Disclosed is a vehicle detection system comprising a transmitter coupled to a receiver via a sensor arranged to produce a change in the envelope of the received signal upon passage of a vehicle. In order to distinguish between changes in the received signal caused by variations in the environmental conditions and the approach of a vehicle, the system is provided with an identification circuit which periodically samples the received signal. The sampled voltages, which are representative of the envelope of the received signal, are then stored and supplied to a comparator which compares the envelope with the sampled voltage and provides an output signal indicating approach of a vehicle when the difference between the envelope level and the sampled voltage exceeds a predetermined value.

Abstract: An eddy current flaw detector is held in a mounting block by a spring bias, the mounting block is selectively rotatable about a shank member for varying the radius of the detector as the shank rotates about a pivot point, turned by an electric drive mechanism.

Abstract: A temperature-responsive circuit comprising an ECTS reed switch and an interrogation means for determining the operability and accuracy of the temperature-responsive portion of the circuit.

Abstract: Magnetic detection means for protection of articles such as books, records and the like, wherein a target, of magnetically soft or easily saturable magnetic material, such as permalloy foil, is mounted on the protected article and emits magnetic signals which are harmonics of an interrogating magnetic field generated at an exit station. The target is curved along its length and provides good signal response over a wide range of orientation.