Abstract: A dual time base, zero dead zone time domain reflectometer repetitively launches a predetermined number of stimulus pulses into a transmission system in synchronism with clock signals from a first time base, providing a measurement cycle. The duration of the launched stimulus pulses, determined by a predetermined number clock cycles from the first time base, exceeds the total propagation time of the system to be measured so that a time interval between a launch and a reflection may be measured within the launched pulse. A second time base, which has a predetermined period that differs from the period of the first time base and defines a measurement period divided into equal sub-periods, continuously produces clock signals, one or more of which may be counted during the time interval.

Abstract: A method and apparatus for detecting and locating fluid leaks, particularly liquid leaks, and determining whether the leaking liquid being detected is a non-conductive liquid such as a hydrocarbon or a conductive liquid such as water utilizes a composite detection cable having a pair of insulated conductors and a pair of uninsulated conductors. Pulses are applied to the insulated conductors and leaks are detected and located utilizing time domain reflectometry (TDR) techniques. The resistance between the uninsulated conductors is measured to determine whether or not the leak is conductive.

Abstract: A method and apparatus for the measuring of a delay in a delay circuit by making a continuous frequency measurement is proposed. The phase-locking of a variable frequency signal applied to the delay circuit allows the user to significantly improve the precision and accuracy of the time delay measurement. A scheme to extract the number of cycles stored in the delay circuit is also disclosed.

Abstract: A dual time base, zero dead zone time domain reflectometer repetitively launches a predetermined number of stimulus pulses into a transmission system in synchronism with clock signals from a first time base, providing a measurement cycle. The duration of the launched stimulus pulses, determined by a predetermined number clock cycles from the first time base, exceeds the total propagation time of the system to be measured so that a time interval between a launch and a reflection may be measured within the launched pulse. A second time base, which has a predetermined period that differs from the period of the first time base and defines a measurement period divided into equal sub-periods, continuously produces clock signals, one or more of which may be counted during the time interval.

Abstract: A token ring local area network (LAN) testing apparatus is provided. The apparatus utilizes time delay reflectory (TDR) in testing cable conductors that link or interconnect stations on the token ring with the token ring media access unit (MAU). In making the TDR related measurements, a directional coupler device is used in transmitting and receiving signals relative to the cable conductor. Information related to the magnitude and location of any cable conductor fault that is obtained. A TDR measurement can be used to determine the existence of a fault at the end of a cable conductor. A single matching impedance element is selected to match the impedance of the cable conductor before conducting any TDR measurement.

Abstract: A parallel plate transmission line (20) is formed by conformal application of one or more dielectric and conductive layers to the surface under test (70). A signal generator (42) is employed to transmit variable frequency signals (60) along the transmission line (20). Discontinuities in the transmission line (20) cause reflections (62) which are received by a receiver (48). A processor (44) coupled to the signal generator (42) and receiver (48) detects and locates the discontinuities.

Abstract: Time Domain Reflectometry ("TDR") methods and apparatus for measuring propagation velocities of RF pulses to determine material liquid contents, moisture profiles, material levels and dielectric constants including: i) TDR probes and/or probe adaptors, including series averaging probes and multi-segment probes, all employing remotely operable, normally open, variable impedance devices such as diodes; ii) bias insertion and switching networks for rendering selected normally open variable impedance devices conductive one at a time to establish precise unambiguous timing markers T.sub.1 . . . T.sub.

Abstract: A PN modulated signal is applied to an end of a network electrical distribution circuit. The signal produces a snapshot trace of energy reflected from various discontinuities along the circuit, including a fault. Because the fault absorbs a large part of the energy in the applied signal, reflections from discontinuities in the same branch as the fault but farther from the input are reduced in amplitude. By knowing the position of the branches and various discontinuities, such as transformers, the position of the fault can be logically determined. If the fault is a high resistance fault a high voltage pulse is applied to the end of the circuit. The PN signal is initially sensed at a time when the fault has a low resistance because of arcing due to the high voltage pulse.

Abstract: A corrosion resistant cable for use in electrical detection systems for fluid leaks in pipelines and the like includes a central electrical conductor, annular spacer means of electrically insulating material disposed around the central conductor, the annular spacer having a plurality of void spaces for receiving leakage fluid, and an annular sheath disposed around the spacer in concentric relation with the central conductor, the annular spacer formed of a plurality of electrically conductive wires, said wires having a coating of corrosion resistant material for protection against water, acids, alkalis, solvents or other liquids or environmental contaminants that may be present in the vicinity. An uninsulated wire may be incorporated in the sheath to cooperate with an uninsulated central conductor to detect conductive liquids, thereby allowing a leak detection system utilizing the cable to distinguish between leaks of conductive and non-conductive liquids.

Abstract: An inverse scattering processing method with enhanced noise immunity and resolution capabilities for use in modeling multi-layer acoustic, electromagnetic or other propagating media. A time bounded filtering step is incorporated within a peeling method for use in processing TDR characteristic waveforms of the propagating media.

Abstract: By measuring the waveform of the reflected wave obtained by transmitting a pulse to an open-ended transmission line, a transfer function of the transmission line with respect to the incident wave is computed as a result of the measurement. Then, the waveform of the output wave at the output end or the open end of the transmission line is estimated in response to an individual input signal by using the transfer function computed. The transmission delay time of the transmission line is obtained by computing the time difference between the transient timing of the estimated waveform of the output wave and the transient timing of the waveform of the input signal.

Abstract: Two or more rising pulse waves having different rates of voltage increase are applied to a measuring end of a cable and reflected waves from a fault point on the cable are detected to measure a turnaround propagation time between the measuring end and the fault point. Additionally, ratios of the rates of voltage increase of one pulse wave and the other pulse waves are calculated. A discharge delay time at the fault point is calculated from time differences of the measured turnaround propagation time and the ratios of the voltage increasing speeds and the discharge delay time is subtracted from the measured turnaround propagation time to calculate a real turnaround propagation time.

Abstract: A method and apparatus for locating an incipient fault at a point along the length of an insulated power line includes the application of an excitation voltage at an open end of the power line, and the signal pulse transmitted along the power line to the open end is passed through a high pass filter to remove the portion of the signal which is at a frequency below the excitation voltage and its harmonics. The filtered signal is amplified and passed through a band pass filter to remove a high frequency portion of the signal containing a large proportion of noise relative to the frequency of the partial discharge frequency from the incipient fault. This filtered signal is passed to a digital storage device adapted to be triggered by a signal of a predetermined amplitude, and the triggered digital storage device receives the amplified signal directly from the amplifier and stores digital data concerning amplitude and time for the peaks of the amplified signal for a predetermined period of time.

Abstract: An automotive electrical system including a wiring harness incorporates the dedicated test line passing through critical connectors and components for allowing detection and isolation of improperly connected connectors. The dedicated test line can feed through expansion connectors, termination connectors, and junction blocks. Connector fault detection and isolation is achieved using time-domain reflectometry after final assembly, during vehicle servicing, or on-board during vehicle usage. A large number of expensive and inconvenient vehicle quits and tow-in's are avoided that would otherwise occur.

Abstract: In an apparatus for determining the moisture content of a material by measuring the dielectric constant of the material by means of a measuring conductor which is disposed such that the material becomes a dielectric for the measuring conductor and wherein the time lapse between the application of an electrical signal to the measuring conductor and the return of the echo of the signal is employed as an indication of the dielectric constant and consequently the moisture content of the material, the electrical signal is a pulsed signal with a pulse duration which is greater than the time lapse between signal start and return of the echo of the signal start and an independent oscillator is provided whose cycles are counted during the opening state of a gate circuit which is open between the application of electrical signal to the measuring conductor and the return of the echo thereof, the counted cycles thereby providing an indication for the time lapsed from signal start to echo return in a simple manner with si

Abstract: A structure integrity monitoring apparatus and method for use with certain structures such as air-frame structures. A meandering transmission line (22) or serpentine coaxial cable is adhered to a dielectric substrate (20). The dielectric substrate may be a composite panel of the air-frame structure. A microwave signal is introduced at one end of the transmission line (22) or coaxial cable and absorbed at the other end by an appropriate signal absorbing device. For use of the meandering transmission line (22), generally two conductors (22, 24) are affixed on opposite sides of the dielectric substrate (20). In this manner, an electric field created by the two conductors (22, 24) by the microwave signals propagating through them is confined within the dielectric substrate (20). As the signals travel down the transmission conductors (22, 24), they will be reflected at crossover points along the way creating a signature reflection wave.

Abstract: A method of locating an intermittent electrical fault in an optical undersea transmission system, comprises measuring the time difference between two signals emanating from the fault along two different routes of the system. In one embodiment one of the signals is a voltage transient and the other signal is an optical error signal created in a repeater adjacent the fault as a result of surge protection in the repeater responding to the electrical fault, and in another embodiment both signals are optical signals, once again emanating from adjacent repeaters and caused by the effect of the electrical fault on the adjacent repeaters. It is envisaged that such a transmission system could be permanently provided with apparatus to detect such a fault in which synchronized counters are permanently running and frequently re-set and which stop in response to error signals being received from a fault when it occurs.

Abstract: In a method and apparatus for detecting and locating a quench zone in a superconducting coil, a sensor is positioned adjacent to and in heat transfer communication with the entire length of the superconducting coil. When a portion of the superconducting coil becomes normal, the adjacent portion of the sensor becomes resistive. A series of electrical pulses sent along the sensor are reflected back by the discontinuity in impedance which occurs at such a normal zone. The reflected pulses and echo pulses produced by various terminations on the sensor are detected by an associated receiver and processor which calculates the location of the resistive zone along the sensor and the corresponding quench zone along the superconducting coil using information derived from the pulses. A second embodiment provides two sensors which are adjacent to and in heat transfer communication with the coil which are pulsed from opposite ends.

Abstract: A leak detection cable for selectively sensing liquid organic chemicals is not affected by liquid water or water vapor. The cable includes a first electrical conductor and a second electrical conductor disposed in a coaxial or twin lead configuration. In the coaxial configuration, a porous insulation layer is disposed between the conductors, and a vapor-proof insulation layer surrounds the conductors. In the twin lead configuration, the conductors are encapsulated in a porous insulation layer which is surrounded by a vapor-proof insulation layer. The vapor-proof insulation allows passage of liquid organic chemicals while excluding water vapors and liquid water. The vapor-proof insulation includes a microporous insulation such as expanded, microporous polytetrafluoroethylene (ePTFE) which has been impregnated with a wax which is soluble in the liquid organic chemicals being detected.

Abstract: Apparatus and method for determining the electrical length of a signal flow path, such as a twisted-pair conductor, to create conductors of the same electrical length are disclosed. The term electrical length refers to a certain physical distance for a length of conductor for which an electrical signal travels, or propagates along the conductor, in a specified amount of time. The apparatus preferably includes a Time Domain Reflectometer 25 (including pulse generator means 30 and electrical response display means 20) which is cooperatively connected to a first end of a conductor pair 51 under test. The conductor pair 51 is inserted through a ground plane 60 or other impedance changing device. Means to mark or cut 62 the conductor 51 are located within the ground plane 60 or as close as possible to the point at which the impedance is changed. Processing means 40 are utilized to adjust the conductor 51 length relative to the ground plane 60.

Abstract: Measurements for inductance and capacitance at various frequencies have been made on semiconductor device to determine inductance of the leads of the device. The measurement methods involve a Time Domain Reflectometer in a unique application in which the leads of the device being measured are submerged in a liquid during measurements.

Abstract: A system component in an RF power amplifier output circuit which has suffered an impedance failure, including antenna, antenna interface system component and interconnecting cables, is identified by the present invention. The RF signal from the power amplifier is outputted to the system components system components in question. A bidirectional coupler detects the voltage wavefront of the outgoing power amplifier output signal and the voltage wavefront of the reflected RF signal caused by an impedance fault. The beginning of a forward voltage wavefront is used to trigger a timing device which continues timing until the beginning of the reflected voltage wavefront is detected. The RF signal is used as the time base for the timing device. The time between the beginning of the forward and reflected voltage wavefronts is therefore a measure of the distance between the voltage detection point and the impedance failure.

Abstract: A leak detection system and method are disclosed in which an electrical circuit uses time domain reflectometry techniques to monitor one or more leak detection cables for impedance changes which are caused when a cable is contacted by a leaking liquid. The circuit of the system includes an electrical pulse generator means for generating a single electrical launch pulse, and for selectively transmitting the launch pulse down one of the cables. A delay means responsive to the launch pulse produces a reset signal upon the transmission of the launch pulse. A sensing means connected to a selected cable produces a trip signal upon receiving a reflected launch pulse which exceeds one or more predetermined thresholds. A latch means connected to the sensing means latches (sets) upon receiving the trip signal and unlatches upon receiving the reset signal. A counter means which is responsive to the reset signal and the trip signal measures a time difference therebetween.

Abstract: A method of and system for automatically determining length, attenuation, impedance and existence of bridge taps on installed communication cable having access to only one end of the cable. A waveform, which includes incident and reflected pulses, is analyzed to determine the presence of significant pulses. The presence of only one positive significant pulse indicates the absence of any discontinuities and facilitates the calculation of a signal-to-noise ratio which determines whether the cable will support the operation of digital communication thereon. The presence of more than one positive significant pulse or a negative pulse indicates the presence of at least one fault on the cable which prevents the operation of digital communication on the cable.

Abstract: Method and apparatus for detecting and sectionalizing troubles on telephone lines automatically. Specifically, an embodiment for detecting and sectionalizing troubles on a telephone line connecting a switching machine and a subscriber telephone set connected thereto over the telephone line, includes apparatus which: (a) emits a pulse over the telephone line; (b) detects reflections of the pulse; and (c) and determines whether a reflection was received prior to the expiration of a predetermined time period. The predetermined period relates to a distance which is less than the length of the telephone line between the switching machine and the subscriber telephone set.

Abstract: In a fault detecting system suitable for the carrier band type LAN regulated by IEEE, and employed in each of stations coupled with each other via LAN, there are provided: a signal trail detector for detecting a signal trail of a solicit-successor frame contained in a transmission signal thereby to produce a trail start-timing detection signal; a carrier detector for detecting a carrier signal component contained in a reflection signal of the signal trail, which has been reflected from a fault occurrence place on the local area network, within a response window frame, thereby to produce a reflection end-timing detection signal; a timer unit for measuring a time period after the trail start-timing signal is produced from the signal trail detector until the reflection end-timing detection signal is produced from the carrier detector; and, a processor for processing the time periods derived from the timer unit of the fault detecting systems employed in the first and second stations so as to calculate a distance

Abstract: Location of a fault in electrical conductors from a terminal position which may be remote from the fault using at least a broad band pulse generator to generate a pulse at a terminal position. It also uses a voltage source at the terminal position capable of inducing a change of impedance at the fault and time measuring means also at the terminal position. The method involves generating a first pulse at the terminal position which is propagated down the conductor and reflected back to the terminal position from various impedance discontinuities, including the impedance discontinuity of the fault, if present. The pattern of reflections from points along the conductor up to the fault resulting from the first pulse are recorded. Then sufficient voltage is applied to the cable to induce a change in impedance at the fault.

Abstract: A method for measuring the impedance of a transmission line. The length and D.C. loop resistance of the line are measured. A pulse is transmitted along the line, the pulse having a duration greater than the time required for it to propogate from its source to the end of the transmission line and reflect back to the source. The transmitted and reflected pulses are monitored and the resultant readings converted to a gross impedance measurement. The measurement is then corrected for the "dribble up" effect. The magnitude of the correction is a function of D.C. loop resistance of the line. The corrected measurement is an accurate measurement of line impedance.

Abstract: Apparatus (1) for performing an electrical test on a cable (3) used in local area networks (LAN's). A source (37) produces electrical signals transmitted through the cable. A resistance circuit (43) is interposed between the source and the cable. The amount of resistance interposed by the resistance circuit is adjusted using an adjustment circuit (67). A sensor (71) senses a characteristic of the signal and determines when that characteristic has a value representing an inpedance match between the source and the cable. The sensor circuit provides a command to the adjustment circuit to thereafter maintain the point of adjustment at which the impedances are matched.

Abstract: A cable tester, which is adapted to be used by persons not expertly skilled in the technical characteristics of local area networks (LANs), is disclosed. The tester incorporates a time domain reflectometer which starts a counter upon the generation of an incident signal pulse and utilizes a comparator which compares signals present on a cable under test to a controllable amplitude to halt the timer. The tester exhibits an output impedance which is greater than the impedance of a cable being tested. The tester additionally measures instantaneous amplitude levels of signals present on the cable being tested, resistance, continuity, noise levels, and data activity on a network of which the cable is a part. In addition, the tester includes a display and a sound generally device. Software programming compensates for impedance mismatches with the cable and data present on an active network being tested.

Abstract: A positional information generating apparatus comprises a code disposed on a main track on which M-sequence codes form a cyclic code of different code words, and sensors disposed for attaining relative movement with reference to a direction of the main track. The code word is detected from the main track by the sensors for generating positional information. A sensor array for the main track in which a greater number of sensors than the number of elements of a code word are disposed over a span corresponding to a length of one code word in such a way that at least one sensor is located on each code element to define a code word to be read. A relative position detector is provided for detecting a relative positional relationship between the sensor array for the main track and the main track.

Abstract: A system for leak detection in underwater structures wherein each critical leakage test point is maintained dry by an enclosure and a test cable is led down through the series of enclosures in fluid-tight manner to support a test probe within the dry test point volume. The test cable is a coaxial cable of selected characteristic impedance and each probe consists of a spirally wound, open-end dual pair supported on a plastic stub so as to constitute a parallel resonant circuit at a selected frequency. Thereafter, a test pulse is conducted down the coaxial cable and the impedance of any probe will be altered by the presence of water to produce a reflected pulse back up the coaxial cable to be detected and input to gating and counting circuitry to determine signal travel duration and, therefore, distance along the cable, as processing, printing and readout components provide output indications.

Abstract: A pocket-size Time Domain Reflectometer is described. The pocket-size Time Domain Reflectometer consists of a pulse generator for producing a test pulse along with a delay line for delaying the test pulse before it is transmitted to a cable whose impedance characteristics are to be determined along its entire length. A test connector outputs the delayed test pulse to the cable that is being tested and the test connector receives reflections of the test pulse produced by the cable. The delay pulse generator produces a delay pulse having a pulse width identical to the test pulse at a time t after the production of a test pulse determined by the delay adjuster which is set in accordance with the specific point along the length of the cable which is being tested. A reflection sensing device is reponsive to the delay pulse and reflections received by the test connector and produces a reflection output signal which is monitored by a meter.

Abstract: A fluid detection system includes a cable which is capable of being dried easily after coming into contact with the fluid being detected and displays a measurable change in characteristic impedance immediately upon contact with the fluid. The cable comprises an inner conductor and a cylindrical outer conductor disposed in a substantially parallel and coaxial relationship with each other with a dielectric detection layer coaxially disposed between the inner and outer conductors. The outer conductor is of an open braided construction which permits easy passage therethrough of the fluid to be detected. The detection layer comprises a pair of solid dielectric elements stranded around the inner conductor in a double helical configuration and defining an air gap between the two conductors which is adapted to retain the fluid so as to measurably change the characteristic impedance of the cable.

Abstract: A method and apparatus of detecting the locations of incipient faults in an insulated power line which comprises the method steps of opening one end of the power line, if it is not suitably terminated to reflect high frequency pulses, applying an excitation voltage to the other end of the power line at an excitation point, detecting a first high frequency pulse produced by a discharge in the power line and transmitted on the power line to the excitation point, detecting a first reflection of the pulse from the open end of the power line to the point of excitation, detecting the travel time of a reflection of the first pulse from the excitation point to the open end of the power line and return to the excitation point, and dividing the time between the detection of the first pulse and the first reflected pulse by the detected travel time.

Abstract: A leak detector and locator utilizes an electrical cable disposed in proximity to fluid carrying pipes or other area wherein a leak may occur. Pulses are applied to the cable and the reflected waveform is analyzed to detect changes in the characteristic impedance of the cable caused by fluid penetrating the insulation of the cable. A different portion of the waveform corresponding to a different point on the cable is sampled after each pulse is generated and stored until the entire waveform has been sampled and stored. Subsequent samples of the waveform are compared with the stored waveform and a leak is indicated if the subsequently sampled waveform differs from the stored waveform by a predetermined amount.

Abstract: A time domain reflectometer (TDR) for making impedance measurements on a powered transmission line cable system. The TDR is particularly useful for measuring impedance discontinuities on a powered Ethernet system. A negative test pulse is provided to ensure that any positive reflections do not exceed the upper voltage limit of the transceivers. The TDR selectively applies a negative bias to the transmission line cable below the collision detection threshold in order to disable all transceivers and prevent network interference with the TDR measurements. The negative DC bias also provides additional headroom for positive pulse reflections.

Abstract: A system for locating faults on a transmission line by taking measurements at only one end of the line.