Abstract: A locator for determining the depth of a buried electromagnetic marker includes a transmission antenna and two reception antennas. The locator has a major axis and is configured. The transmission antenna is configured to generate an oscillatory magnetic field parallel to the major axis. The first reception antenna of the two reception antennas is configured to couple with an oscillatory magnetic field parallel to the major axis emitted by the electromagnetic marker and to generate a first detected signal. The second reception antenna is displaced along the major axis from the first antenna and configured to couple with an oscillatory magnetic field parallel to the major axis emitted by the electromagnetic marker and to generate a second detected signal. The locator includes analogue to digital converters and a processor which is configured to calculate the depth of the electromagnetic marker.

Abstract: A locator for determining the depth of a buried electromagnetic marker includes a transmission antenna and two reception antennas. The locator has a major axis and is configured. The transmission antenna is configured to generate an oscillatory magnetic field parallel to the major axis. The first reception antenna of the two reception antennas is configured to couple with an oscillatory magnetic field parallel to the major axis emitted by the electromagnetic marker and to generate a first detected signal. The second reception antenna is displaced along the major axis from the first antenna and configured to couple with an oscillatory magnetic field parallel to the major axis emitted by the electromagnetic marker and to generate a second detected signal. The locator includes analogue to digital converters and a processor which is configured to calculate the depth of the electromagnetic marker.

Abstract: A locator for locating a concealed conductor carrying an alternating current having at least first and second frequencies, the alternating current produced by at least one dedicated signal generator. The locator includes at least one magnetic field sensor operable to convert electromagnetic radiation from the conductor into a field strength signal; a digital analog converter configured to generate a digitized signal dependent upon the field strength signals from the magnetic field sensor; a digital signal processor configured to isolate components of the digitized signal resulting from the first frequency and the second frequency; and process the isolated components to generate one or more signals indicative of the proximity of the conductor to the detector; and an output configured to generate an audio and/or visual indication of the proximity of the conductor, wherein the isolated signal components resulting from the first frequency signal and the second frequency signal are contemporaneously processed.

Abstract: A system for detecting a plurality buried conductors includes a transmitter configured to generate an alternating test signal for a plurality of buried conductors. The system further includes a receiver configured to detect an electromagnetic field produced by the alternating test signal in the plurality buried conductors and a remote control configured to control the transmitter to generate the alternating test signal in one of the plurality of buried conductors.

Abstract: A signal generator for coupling to a concealed conductor including a first oscillator configured to generate a first waveform having a first frequency, a first terminal coupled to the first oscillator through a first band pass filter configured to pass signals of the first frequency, a second oscillator configured to generate a second waveform having a second frequency, and a second terminal coupled to the second oscillator through a second band pass filter configured to pass signals of the second frequency.

Abstract: A locator for locating a concealed conductor carrying an alternating current having at least first and second frequencies, the alternating current produced by at least one dedicated signal generator. The locator includes at least one magnetic field sensor operable to convert electromagnetic radiation from the conductor into a field strength signal; a digital analogue converter configured to generate a digitized signal dependent upon the field strength signals from the magnetic field sensor; a digital signal processor configured to isolate components of the digitized signal resulting from the first frequency and the second frequency; and process the isolated components to generate one or more signals indicative of the proximity of the conductor to the detector; and an output configured to generate an audio and/or visual indication of the proximity of the conductor, wherein the isolated signal components resulting from the first frequency signal and the second frequency signal are contemporaneously processed.

Abstract: The present invention provides a time domain reflectometer for testing an electrical cable. The time domain reflectometer includes a test signal generator, at least one line feed resistor, connected between the test signal generator and a pair of terminals, for connection to the ends of the electrical cable under test, and a signal processor, connected to the terminals, to receive a line signal including a reflection of a test signal transmitted into the cable under test. The signal processor is programmed to filter the line signal to enhance a portion of the signal indicative of any fault on the cable by balancing the signal according to the electrical characteristics of a normal cable of the same type as the cable under test by applying a filter function, and acquiring at least one estimate of the input admittance of the transmission line from known or estimated electrical characteristics of the cable under test.

Abstract: The present invention provides a method of time domain reflectometry including transmitting a test signal along a cable under test from one end and sensing and recording a reflected signal from the cable at that end, using the recorded, reflected signal to estimate the distance, Ldist, from the one end to a discontinuity on the cable, separating a test signal component from the remainder, Vr, of the reflected signal; estimating the impedance, Zfault, of the discontinuity from known, predetermined values of the characteristic impedance, Zline, and of the characteristic gain, T, of a reference cable, and from the said separated test signal and reflected signal components, calculating the estimation error as a difference between the model reflection signal, Vrmod, expected of the cable under test based on the characteristic impedance and characteristic gain and the estimated impedance, Zfault and distance, Ldist, and the actual reflection signal Vr, choosing new estimated values of Ldist and Zfault in accordance

Abstract: The present invention provides a time domain reflectometer for testing an electrical cable. The time domain reflectometer includes a test signal generator, at least one line feed resistor, connected between the test signal generator and a pair of terminals, for connection to the ends of the electrical cable under test, and a signal processor, connected to the terminals, to receive a line signal including a reflection of a test signal transmitted into the cable under test. The signal processor is programmed to filter the line signal to enhance a portion of the signal indicative of any fault on the cable by balancing the signal according to the electrical characteristics of a normal cable of the same type as the cable under test by applying a filter function, and acquiring at least one estimate of the input admittance of the transmission line from known or estimated electrical characteristics of the cable under test.

Abstract: A detector for locating a sonde includes a plurality of antennas, an analogue to digital converter 11 and a digital signal processor to isolate the magnetic signal produced by the sonde. The digital signal processor includes a phase feedback loop 21 to allow the digital processing unit to follow variations in the frequency of oscillation of the magnetic signal produced by the sonde.

Abstract: A system for detecting faults in the insulation layer surrounding a concealed conducting pipe (10) includes a signal generator (12) for applying an alternating current with a frequency of around 4Hz to the pipe, a magnetometer (102) for detecting the alternating current from the pipe (10) and a CPU (115) for identifying changes in the gradient of the detected current along the length of the concealed conducting pipe (10) which are caused by the faults in the insulation layer. The magnetometer (102) is used in connection with a locator(100) which detects a second alternating current applied to the pipe (10) by the signal generator (12), this second alternating current having a frequency of around 128Hz. The system can also use both these signals to determine the direction of the signals emulating from the pipe (10).

Abstract: In order to detect if there is a fault in a cable (6), three signals are applied to the cable (6) by a suitable transmitter (FIG. 1). Two of the signals are of high frequency and the other signal is of low frequency equal to an integer multiple of the difference between the frequencies of the high frequency signals. Aerials (10a, 10b) of a receiver (FIG. 2) detect the high frequency signals and the receiver processes those high frequency signals to determine a frequency signal. This is then compared in a comparison circuit (31) with the low frequency signal detected by ground probes (22,23) of the receiver (FIG. 2). At a fault in the cable (6), e.g. where the outer insulation is damaged, the conductor of the cable (6) is shorted to ground and this causes a change in a phase between the signals. Thus by moving the receiver along the cable (6), there will be a change in place at or adjacent the fault which will be detected by the receiver (FIG. 2) allowing the fault to be located.