Abstract: A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet.

Abstract: The invention relates to a method and means for measuring the depth of cracks, using a potential probe connected to a measuring instrument and having two current terminals and additional voltage-measuring terminals (potential probe method).The object of the invention is to eliminate the separate calibration devices needed for the checks and collective measurements necessary when using known potential probes, and to make the check measurements in conjunction with the actual depth-measuring process.This problem is solvable by using a potential probe (S) as per the drawing, where at least two pairs of terminals (1+2, 3+4) having known but different spacings serve as adjustment measuring portions and are connected to an adjustment circuit (JM, UM) in a measuring-instrument microcomputer (M) and an additional pair of terminals (2, 3) having a known spacing serve as a crack-depth measuring portion and are connected to a crack-depth measuring circuit (TM) in the microcomputer.

Abstract: A probe holder mounts a pair of spaced current probes, a pair of spaced primary voltage probes inward of such current probes and a pair of spaced secondary voltage probes outward of such current probes. Each of the secondary voltage probes and the nearer thereto of the primary voltage probes is on the same equipotential contour calculated by assuming that the current probes contact and pass current through a planar homogeneously resistive sheet with infinite boundaries and of infinitesimal thickness. Electroconductive bodies are evaluated for resistive anomalies therein by contacting the body of all the probes and passing current through the body between the current probes. The voltages V.sub.a, V.sub.b and V'.sub.a, V'.sub.b responsively sensed on the surface of such body by, respectively, such two primary probes and such two secondary probes are used to derive first and second signals as functions of the voltage differentials V.sub.a -V.sub.b and V'.sub.a -V'.sub.b respectively.

Abstract: Disclosed is a system that determines whether input and output pins of semiconductor components are present and properly soldered to a printed circuit board. The system includes an oscillator which is connected to a metallic electrode placed on top of an integrated circuit package. A probe pin in a bed of nails tester is connected to a current measuring device and connected to a printed circuit board wiring trace that is soldered to the pin being tested. The oscillator signal is capacitively coupled through the integrated circuit package to the pin being tested, so if current is measured by the current measuring device, the pin is connected to the printed circuit board.

Abstract: A process and apparatus are provided for checking the electric continuity of an electrically conducting material device, in which a current is injected between two points of said device and the resulting voltage between these points is measured. The invention is remarkable in that said current is an AC current and its pulsation is chosen sufficiently large so that the impedance between the two points, measured by the ratio of said voltage and of the current, may be considered as being equal to the product of the inductance of the path of the current between said points multiplied by said pulsation.

Abstract: A digital isolation monitor comprises a digital processing signal processor P1 designed to synthesize a sine wave in real time by a table, and to send the digital values of this sine wave to a digital-to-analog converter of an input channel to generate a low-frequency AC reference signal with a very low, stable phase distortion factor. An acquisition channel is fitted with a switching unit operating in conjunction with a dual measurement circuit to send an injected voltage signal and a leakage current signal to a low-pass analog filter in series with a sample-and-hold circuit and an analog-to-digital converter. The processor P1 then performs synchronous demodulation and transmits the data to a microcontroller P2.

Abstract: A device for the electric characterization of samples, comprises a UHF resonator intended to be coupled locally to the sample. The resonator is formed by a microstrip or triplate line loop (20) carried by a conducting plane (16) and having a gap of small length with respect to the length of the loop and an assembly (32) for receiving the sample in a position in which the sample is coupled selectively to the edges of the gap without being interposed therebetween. The edges of the gap of the loop are fixed to two electrodes of small area passing through a thin plate of dielectric material having a flat face for application against the sample.

Abstract: A technique for measuring the insulation resistance of an insulated rail joint in the presence of leakage ground resistance (ballast resistance), as well as other track run-around paths, without the use of calibrated meters, such technique characterized by the use of a bridge circuit which includes a leg having the insulated joint therein whose resistance is being measured, the other three legs including a resistor of fixed known value and two variable resistors respectively, such that when the variable resistors are varied to obtain simultaneously both (a) the null of the rail, or ballast, current, and (b) ballast in the bridge circuit, the resistance value of the insulated joint is determined.

Abstract: A procedure and a device for determining corrosion of preferably insulated structural parts (2) assures in a simple way early detection of corrosion. For this purpose an electric conducting resistance wire (4) exposed to the same corrosive medium, e.g. condensation water, as the structural part (2) to be examined for corrosion is placed outside the structural part (2) and the electrical resistance of the resistance wire is measured. The effective cross-section of the resistance wire (4) and its electrical resistance change with the corrosion of the resistance wire (4) so that the resistance change of the resistance wire (4) registers the effect of the corrosive medium.

Abstract: The present invention provides a passive superconducting sensor for quench detection in a superconducting coil. The sensor consists of a first circuit electrically connected to two voltage taps of a superconducting coil. The first circuit uses nonsuperconducting components and preferably contains a resistive element. The first circuit is magnetically coupled to a second circuit by a hybrid transformer. The second circuit is superconducting and contains a readout coil and preferably a second hybrid transformer. The second hybrid transformer is magnetically coupled to a sense coil which detects flux changes in the superconducting coil. The readout coil is coupled to a readout device which measures changes in the current through the readout coil. The current in the readout coil can be made a function only of the resistance of the superconducting coil between the voltage turns and thus can be used to detect a quench.

Abstract: According to the present invention, a method and device for detecting failure of heating elements in various jets of a thermal jet printing device is provided. The printing device which includes a plurality of thermally actuated printing jets, each of which jets includes a resistance heating element, is actuated when a current is supplied to generate a bubble. The bubble expands eject a drop of ink. Electrical circuit means are provided including power supply means to supply current to the electrical resistance elements. Control means are also provided to selectively connect the elecrical resistance elements to this power supply in preselected arrays for forming bubbles in selected configuration to perform the ink jet printing. The operation includes a test circuit coupled to the resistive heater elements and operable by the control circuit to generate a failure signal representative of a resistance above a preselected value in any resistance heating elements.

Abstract: A scheme for rapidly connecting and rapidly disconnecting a large number of point contacts onto a pipe surface is taught. The scheme involves pressing sharply pointed pin contacts onto the pipe surface by gas pressure. Each pin is held in a conforming opening in an annular ring structure. The ring forms the inner wall of an annulus capable of holding gas pressure to urge the many needles inward against the pipe surface. Each pin is individually connected to a power supply and sensing apparatus.

Abstract: A sensor for electrochemical measurement is disclosed which includes a chamber made of an electrically insulative material and having an open end portion, a super absorbent polymer material filled in the chamber and absorbing at a selected rate a liquid electrolyte, an electrode disposed in the chamber, and a screen which covers the open end portion of the chamber and which prevents the super absorbent polymer material from dropping out from the chamber but permits the liquid electrolyte to transmit through the screen. A method is also disclosed which uses the sensor to measure the degree of degradation of a coating film on metal or the corrosion protective properties of a rust film created on the surface of steel.