Abstract: The T.sub.2 * effects due to inherent inhomogeneities in the static magnetic field are overcome by the use of a 180.degree. RF pulse to produce a nuclear spin echo suitable for obtaining spatial information and by the adjustment of the pulsed gradients such that the occurrence of the spin echo due to the applied gradients coincides with the occurrence of the nuclear spin echo derived from the rephasing of spins in the presence of the inhomogeneities inherent in the main static magnetic field. The 180.degree. RF pulse is applied with the imaging gradients turned off so that long RF pulse lengths can be used, thus reducing RF power requirements. Exemplary applications of the pulse method to multiple angle projection reconstruction and two-dimensional Fourier transform (spin warp imaging) imaging techniques are also described.

Abstract: A method of measuring the rate of corrosion of a metallic structure that is subjected to a corrosive ambience. It subjects a thin metallic enclosure to the same ambience as the metallic structure is subjected to. The thin enclosure is subjected to the ambience on one side, while it maintains a different condition on the other side of the enclosure. Then, it detects a change when the different condition is no longer maintained due to the thin enclosure having corroded through.A probe for detecting the corrosion rate of metallic piping or the like. It includes a thin metal enclosure mounted with one side subjected to the corrosive ambience acting upon the piping. There is means for subjecting the other side of the thin enclosure to a condition that is different from that of the corrosive ambience. And, there is a means for detecting a change of the different condition when the thin metal enclosure corrodes through.

Abstract: An average frequency measuring apparatus in which auxiliary gate signals are converted into synchronized gate signals synchronized with either input signals or clock signals; first and second gates are opened by the synchronized gate signals; the input signals and the clock signals having passed through the first and second gates are counted by first and second counters, respectively; and the frequency of the input signals is calculated from the count values of the first and second counters for a plurality of occurrences of the synchronized gate signal. A third counter is provided for counting the number of the synchronized gate signals, and a minimum counting time is calculated by calculating means from the count values of the third and second counters and the set measurement accuracy.

Abstract: A detector circuit (10) is programmed to produce an output signal when an input signal is at a predetermined frequency. The input signal is provided to an inverter (14) to produce an inverse signal. The input signal together with the inverse signal are provided to two switches (16, 18). The switches (16, 18) are driven by first and second drive signals produced by a drive generator (60). The output terminals (24, 28) of the switches are alternately connected to the input terminals in synchronism with the corresponding drive signals. The output signals from the switches (16, 18) are transmitted through low pass filters (26, 30) and the resulting signals are combined to produce a summation signal by a summation circuit (36). The summation signal is passed through an absolute value circuit (40) to produce an absolute value signal. The absolute value signal is examined by a threshold detector circuit (44) which produces an output when the absolute value signal exceeds a preset threshold.

Abstract: In a relay tester, analog signals to be supplied to a relay under test are processed with digital circuits so that the concerned frequency, phase, voltage and current are set and adjusted with high frequency.

Abstract: In a probe point device for electrical tests the metallic point proper is carried by a hollow insulating handle or push member on which an insulating head is slidably mounted, spring and abutment means normally maintaining the head at a position of rest at which it wholly covers the point. A fuse cartridge is disposed within the push member to connect the point with the flexible cable provided at the rear of the said member. This cartridge has at its front end an axial indicator button which, when the cartridge blows, acts on a pivoted pawl to engage a first nose thereof into an inner circular groove provided in the head, thus locking the push member with respect to the head at the position of rest. A second tooth of the pivoted point member also locks the push member with respect to the head if the cartridge is missing.

Abstract: An automatic phase compensation circuit is disclosed for use with carrier transducers. A quadrature oscillator drives the carrier transducer and provides phase reference and quadrature reference signals to a phase shifter. The phase shifter provides phase shifted reference signals. The return signal from the carrier transducer is separately demodulated with respect to each of the phase shifted reference signals. The demodulated signal with respect to the phase shifted quadrature reference signal is converted into a DC control signal which controls the amount of the phase shift of the phase shifter. The phase shifter receives the quadrature reference signal into a variable gain amplifier controlled by the DC control signal. The output of the variable gain amplifier is summed with the phase reference signal. The resultant summation is a phase shifted reference signal with the control signal controlling the amount of phase shift.

Abstract: One or more input signals to be processed are summed with a pseudo random noise signal to preserve the signal phase, are placed on a carrier, are processed by a one-dimensional optical spectrum analyzer, and a time history thereof is stored in a digital corner-turn memory in a time/frequency domain. The memory is read with an address map that corner-turns the stored data, where the resulting frequency/time signal then is fed to a second one-dimensional optical spectrum analyzer. Since signal phase is preserved, a two-dimensional analog signal in a frequency/frequency plane is provided.

Abstract: A method and apparatus are provided for indicating an operating characteristic of a periodically combusting internal combustion engine, such as a diesel engine, having exhaust gas issuing from one or more combustion chambers in a periodic manner through a duct. The particulate in the exhaust gas stream are electrically charged and of the same polarity, and are grouped in packets associated with the periodic combustion in the respective chambers. An electrically conductive, passive electrode, preferably annular in shape, is disposed such that most or all of the exhaust gas flows therethrough so as to electrostatically sense, principally by induced image charge, the passage of the respective packets of charged particles. The electrode is electrically isolated from the duct.

Abstract: A frequency counter (20) measures and displays a plurality of frequencies appearing on input channels (22, 24, 26 and 28) of an analog circuit (30). A program switch (32) is coupled to a decoder logic circuit (34) which facilitates the operation of counter (20) in one of a plurality of selectable program modes. A steering logic circuit (36) is coupled to circuit (34) and facilitates the selection and order of the input channels (22, 24, 26 and 28) during a measurement cycle. Toggle switches (38, 40 and 42) are coupled to circuit (36) to facilitate the establishment of a sign bit, a channel order and a channel select, respectively. A channel display circuit (46) provides visual indication of the sign, channel select and channel order.

Abstract: A scheme for measuring the frequency of an alternating current signal provides for the development of first and second values which are respectively representative of the time the alternating current signal exist in alternate half cycles; e.g., the period of a half cycle. The most recently developed of the first and second values is retained and continuously compared with the other value which is presently being developed to thus provide an output signal representative of the greater thereof. This output signal is indicative of the period and, hence by its reciprocal, a measure of the apparent instantaneous frequency of the alternating current signal.

Abstract: The true electrical channel length of a surface FET is determined by obtaining individual electron-beam-induced-current signal traces of source and drain junctions, thus eliminating the coupling effect of the two junctions. A reliable mask is formed as a function of the measured peak-to-peak distance subtracted by the depletion width.

Abstract: In a spectrum analyzer, an intermediate-frequency oscillator and the outputs from a sweep oscillator are frequency mixed to obtain a measuring signal, which is provided to a device under test. The intermediate-frequency signal and the output from the intermediate-frequency oscillator are supplied to a phase detector to detect a phase difference between them. A signal representing the detected phase difference and the output from a detector are selectively applied by a switch to a display.

Abstract: A method and apparatus for electrically testing individual elements of multi-cell batteries comprises sequentially locating batteries at a test location whereat they are engaged by test probes which are sequentially associated with a testing device which tests the individual cells. If faults are detected, the individual faulty cell is marked. Auxiliary test indicator lights provide a visual indication of the individual testing of each cell as it occurs.

Abstract: An unbalanced current detector for a three phase electrical system of the type including a current transformer (4, 6, 8) for each phase (.phi.A, .phi.B, .phi.C) and a burden resistor (16) which receives a rectified output of the current transformer is disclosed. The harmonic content of a rectified ripple voltage developed across the burden resistor (16) is applied to a filter (20) for extracting desired frequencies and rejecting other frequencies, and the filter output is applied to a level detecting and amplifying circuit (54) the output of which is applied to an indicator (77) to indicate an unbalanced current condition.