Abstract: Apparatus for magnetic testing of sheet or strip includes a magnetizing system comprising spaced arrays of substantially parallel rectilinear conductors supported adjacent the plane of sheet or strip to be tested, the conductors being connected to carry magnetizing current so that the fields generated by the arrays are opposed.

Abstract: A conductive object detector having an eddy current killed oscillator, wherein the oscillator output is stabilized by means of a proportional plus integral controller. The controller proportional gain is set low and the integral time long, hence a conductive object near the oscillator will "kill" it, whereas the controller will minimize the effect of temperature or aging on the oscillator output.

Abstract: A linearizing circuit is provided for a non-destructive testing instrument having circuit means developing a DC voltage having a non-linear relationship to units of measurement or of conductivity or some other characteristic measure. A plurality of linearizing stages are provided each including an adjustable resistance connected between a reference voltage source and an output line when the potential of the output line is between the reference voltage and one limit of the DC voltage. Preferably, an analog switch is provided in series with the adjustable resistance and is controlled from an operational amplifier, with a second operational amplifier being provided having an output connected through the analog switch and the adjustable resistance to the output line. The circuit is very accurate and reliable and is readily adjusted by a method wherein the resistances are adjusted in accordance with reference voltages in a certain sequence to obtain accurate adjustment with no juggling operation.

Abstract: This distance measurement system employs the principle of electromagnetic induction to sense distances between an inductive transducer and an object. The inductive transducer forms a part of a signal phase network, and a means for comparing the signal of the inductive transducer to a reference signal provides linear output of the dimension between the transducer and an object. A circuit element such as a capacitor is connected in parallel with the inductive transducer to enhance the sensitivity and resolution of the measurement, to significantly reduce or eliminate error due to temperature, and to provide a high degree of output linearity relative to the distance measured.

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: Conductivity measuring instruments are provided in which a test coil is supplied with alternating current and a detector responds to the voltage across the test coil to develop an analog voltage which is applied to a linearization circuit to develop an output voltage as a linear function of conductivity, the output voltage being applied to a digital read-out unit. As a function of conductivity, the analog voltage is single-valued, preferably with no more than a gradual slope change over a wide range of conductivity values. In one embodiment, a high impedance is provided in series with the test coil, the detector is a phase detector operated to respond primarily to the inductive component and linearization circuit is of a diode-function type. Alternatives are in the use of a phase-to-voltage type of detector and in the use of a digital type of detector and in the use of a digital type of linearization circuit.

Abstract: An inductively coupled oscillator method for inducing eddy currents in a semiconductor PN junction wafer while irradiating said wafer with pulsed light of selected intensity. The oscillator loading due to the pulsed light modulated eddy current losses is monitored and displayed on an oscilloscope in the form of a decay time plot of voltage amplitude, the plot being a function of the pulsed light intensity and the recombination rate of light-induced electrons and holes on each side of the junctions. The leakage characteristics of the junctions which are desired to be measured are one of the factors determining said rate. Leakage characteristic is made the predominent factor by setting the intensity of the pulsed light to a value which produces a nearly straight line decay time plot on the oscilloscope display. The slope of the line then is a measure of the leakage characteristic.