APPARATUS AND METHOD FOR DETECTING CRACKS IN COATINGS

Abstract

An apparatus and method for identifying breaks in a coating, comprising a generator having two contacts with a coating and pulsing current to one of the moving contacts. A plurality of detected electrical signals are processed to continuously generate a baseline indicative of a break. A break signal is activated when a signal is detected which, compared to the generated baseline, indicates a break. A plurality of types of electrical signals and baselines, such as current and voltage, can be detected separately, with a break signal activated when any type of signal is detected which, compared to its generated baseline, indicates a break. The moving contact can be flexible to adapt to the contour of the coating.

Description

APPARATUS AND METHOD FOR DETECTING CRACKS IN COATINGS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable. RESEARCH OR DEVELOPMENT SPONSORED BY THE FEDERAL GOVERNMENT

[0002] Not applicable. MICROFICHE / COPYRIGHT REFERENCE

[0003] Not applicable. FIELD OF INVENTION

[0004] A method and device for detecting breaks (perforations) in electrically insulating material. BACKGROUND OF THE INVENTION

[0005] Conventional crack or perforation detection employs a device that includes a high-voltage source connected to two or more electrodes located on the surface of the insulating layer. An electrode is swept along the surface being tested, and when a crack in the insulating layer is encountered, a spark jumps from the electrode to the perforation. A detection mechanism identifies any spark event and typically alerts the operator (e.g., ML / t / ZUZ4 / U 1 i / zy by means of an audible sound and / or a visual indication) who can then note the location of the electrode as the location of a break.

[0006] The high-voltage source has been either direct current (DC) or alternating current (AC), although typically the voltage has been pulsed (AC), with each pulse reaching its highest voltage for a short time. The high-voltage source is usually pulsed at a rate fast enough to ensure that the test area is covered while the user pulls or pushes the electrode. Particularly with AC pulses, the detection mechanism must be able to reliably differentiate a normal pulse discharge (without breaks) from a spark (breaks), typically based on changes in the amplitude of the current or voltage detected during the absence and presence of a spark.

[0007] Unfortunately, conventional detection mechanisms have often struggled to reliably detect a break. These mechanisms are sensitive to changes in the current flowing in the wire from the pulse generator to the brush (as a function of time), and they operate based on inductive coupling, which is not sensitive to changes in electrical charge. Breaks cause a transient in the current and the electrical charge accumulated around the electrodes. Since the current The current in the cable is proportional to the impedance between the brush and the coating. When a break is encountered, the impedance changes instantaneously, and the amplitude of the detected current reflects this change. These detection mechanisms determine whether the maximum current amplitude exceeds a threshold indicative of a break and, when the threshold is exceeded, generate an audible sound and / or a visual indication to show that the electrode is located at a break.

[0008] However, similar current changes can result from impedance changes occurring for reasons other than a spark, and such impedance changes can be indistinguishable from those resulting from a break. For example, when the electrode is swept across the insulating surface, there are instantaneous variations in the current or voltage imparted to the electrodes, and these normal variations have frequently been flagged as breaks even if there are no sparks or perforations in the insulating surface or coating. In addition, changes in the conductivity of the soil beneath the coating cause variations that have fooled detection mechanisms and produced false positives (false indications of a spark / perforation).

[0009] Conventional crack detectors have allowed the user / operator to manually adjust the sensitivity level (i.e., the maximum current amplitude threshold chosen to indicate a spark) to minimize false positives. However, such adjustments do not fully address false positives and false negatives. That is, although the threshold can be manually adjusted, such adjustments are only approximations of the appropriate threshold over a given area. Therefore, while the threshold can be adjusted to ensure that the detector is sensitive enough to signal a positive when a crack is known to exist, but not so sensitive as to signal a positive when a crack is known not to exist, such a threshold may not be appropriate in other areas of the coating where different conditions exist (e.g., different soil detection, changes in brush contact).In summary, when cracks are detected in a coating, even a threshold selection that works well in one area of ​​a coating may not be suitable for other areas, resulting in cracks being missed and / or cracks being indicated when no cracks exist.

[0010] The apparatus and method described herein significantly overcome the disadvantages of the previous technique described above. SUMMARY OF THE INVENTION

[0011] This document describes a method and apparatus for detecting breaks in electrically insulating surfaces. The apparatus is a portable device comprising a high-voltage generator, at least two movable electrodes that deliver a charge to the coating, and a detection mechanism capable of identifying breaks under a wide range of varying environmental or operating conditions, whether due to electrode movement, variable soil resistivity, or other factors. The break detector uses intelligent signal processing to minimize environmental variability and accurately mark breaks without the need for manual adjustments.

[0012] One aspect of the invention is a method for detecting breaks in a coating, comprising the steps of (a) creating a circuit for current from a generator to a first contact with the coating to a second contact spaced from the first contact to the generator, the second contact being an electrical reference for the generator, (b) driving current from the generator to the first contact of the coating as the first contact moves over the coating, (c) detecting a plurality of at least one electrical signal associated with the pulsating current from the electrical reference, (d) continuously processing a recently selected plurality of the detected electrical signals to generate a reference value for at least one electrical signal,wherein a detected electrical signal having a value on one side of the baseline is considered to indicate no breaks and an electrical signal having a value on the other side of the baseline is considered to indicate a break, and (e) activating a break signal when at least one of the detected electrical signals has a value on the other side of the baseline.

[0013] In one embodiment of this aspect of the invention, the second contact is with the top of the cladding. In an alternative embodiment, the second contact is with the ground beneath the cladding.

[0014] In one embodiment of this aspect of the invention, the lining has an electrically conductive upper surface and lower surface, and the first and second contacts are in contact with the upper surface of the lining. In another embodiment, the lining is a geomembrane in a geotechnical site. In yet another embodiment, the geomembrane comprises a plurality of linings joined together by seams.

[0015] In another form of this aspect of the invention, the at least one electrical signal is a selected one between current intensity and voltage.

[0016] In another embodiment of this aspect of the invention, the at least one electrical signal comprises both current and voltage, wherein the detected current is continuously processed to generate a baseline current and the detected voltage is continuously processed to generate a baseline voltage. In another embodiment, the break signal is generated when the current or voltage exceeds its generated baseline.

[0017] In yet another form of this aspect of the invention, at least one energy averaging, filtering and Fourier spectrum is used to generate the baseline from the recent plurality of detected electrical signals.

[0018] Another form of this aspect of the invention includes the baseline being a selected value greater than an average of the recent plurality of detected electrical signals.

[0019] Yet another form of this aspect of the invention includes that the activated breakage signal is at least one of an audible sound and a warning light.

[0020] Yet another embodiment of this aspect of the invention includes that the activated break signal is a location indication corresponding to the area of ​​the cladding that is in contact with the first contact at the moment the detected electrical signal has a value on the other side of the baseline. In another embodiment, the activated break signal is at least one of a grid coordinate signal on the cladding, an audio signal, a visual signal, and a GPS coordinate signal.

[0021] In another aspect of the invention, a sensor for detecting breaks in a coating includes a pulse generator with an electrical reference, an electrode adapted to move and maintain contact with the coating spaced from the electrical reference of the generator while the generator pulses current to the electrode, a processor, and a break signal that is activated when any detected electrical signal has a value on the other side of the baseline.The processor is adapted to detect over time from the generator's electrical reference at least one electrical signal associated with the pulsating current, to continuously process for a selected recent time period the at least one electrical signal detected during the selected time period, and to generate a baseline of the at least one electrical signal, wherein a detected electrical signal having a value on one side of the baseline is considered to indicate no breaks and an electrical signal having a value on the other side of the baseline is considered to indicate breaks.

[0022] In one form of this aspect of the invention, the electrical reference can be placed on the cladding.

[0023] In another form of this aspect of the invention, the processor is adapted to detect a selected current intensity and voltage.

[0024] In another embodiment of this aspect of the invention, the processor is adapted to detect both current and voltage, continuously processing the current to generate a current baseline and continuously processing the voltage to generate a voltage baseline. In another embodiment, the break signal is activated when the detected current or voltage falls outside its generated baseline.

[0025] In another form of this aspect of the invention, the processor is adapted to use at least one energy averaging, filtering, and Fourier spectrum to generate the baseline from the recent plurality of detected electrical signals.

[0026] In yet another form of this aspect of the invention, the activated breakage signal is at least one of an audible sound and a warning light.

[0027] In yet another form of this aspect of the invention, the break signal is a location indication corresponding to the area of ​​the coating that is in contact with the electrode at the time when the value of the detected electrical signal is on the other side of the baseline.

[0028] In another aspect of the invention, a method for detecting breaks in a coating includes the steps of (a) creating a current circuit from a generator to a first contact with the coating to a second contact spaced from the first contact to the generator, the second contact being an electrical reference for the generator, (b) sending current from the generator to the first contact of the coating when the first contact moves over the coating, (c) detecting the current intensity and voltage at the electrical reference of the generator, (d) comparing a reference current intensity with the current intensity at the electrical reference of the generator, (e) comparing a reference voltage with the voltage at the electrical reference of the generator,and (f) activate a break signal when either the current intensity or voltage has a value that is on one side of its baseline is considered to indicate a break.

[0029] In one embodiment of this aspect of the invention, the lining has an electrically conductive upper surface and lower surface, and the first and second contacts are in contact with the upper surface of the lining. In another embodiment, the lining is a geomembrane in a geotechnical site. In yet another embodiment, the geomembrane comprises a plurality of linings joined together by seams.

[0030] In another embodiment of this aspect of the invention, the detected current intensity is continuously processed to generate the current intensity baseline, and the detected voltage is continuously processed to generate the voltage baseline. In another embodiment, the break signal is generated when the current intensity or voltage exceeds its generated baseline.

[0031] In yet another form of this aspect of the invention, at least one energy averaging, filtering and Fourier spectrum is used to generate the baseline from the recent plurality of detected electrical signals.

[0032] In yet another form of this aspect of the invention, the baseline is a selected average of the recent plurality of detected electrical signals.

[0033] Another form of this aspect of the invention includes that the activated breakage signal is at least one of an audible sound and a warning light.

[0034] Yet another form of this aspect of the invention includes that the activated break signal is a location indication corresponding to the area of ​​the cladding that is in contact with the first contact at the time when the current intensity has a value on one side of the current intensity baseline that is deemed to indicate a break or the voltage has a value on one side of the voltage baseline that is deemed to indicate a break.

[0035] In another aspect of the invention, a sensor for detecting breaks in a coating includes a generator with an electrical reference that can be placed on or adjacent to the coating, an electrode adapted to move over the coating and maintain contact with the coating spaced from the electrical reference of the generator, while the generator sends current to the electrode, a detector that detects the current intensity and voltage at the electrical reference of the generator, and a processor adapted to (i) compare a reference current intensity with the current intensity at the electrical reference of the generator, and (ii) compare a reference voltage to the voltage at the electrical reference of the generator.A breakdown signal is activated when the detected current intensity has a value that is on one side of its reference current intensity that is considered indicative of a breakdown, or the detected voltage has a value that is on one side of its reference voltage that is considered indicative of a breakdown.

[0036] In one embodiment of this aspect of the invention, the processor is adapted to continuously process the current intensity to generate the baseline current intensity, and to continuously process the voltage to generate the baseline voltage. In a further embodiment, the processor is adapted to utilize at least one method of power averaging, filtering, and Fourier spectroscopy to generate the baseline from the recent plurality of detected electrical signals.

[0037] In another form of this aspect of the invention, the break signal is activated when the detected current intensity or detected voltage is on the side of its generated baseline that is deemed indicative of a break.

[0038] In yet another form of this aspect of the invention, the activated breakage signal is at least one of an audible sound and a warning light.

[0039] In another form of this aspect of the invention, the break signal is a location indication corresponding to the area of ​​the coating that is in contact with the electrode when the detector detects at least one current intensity and voltage that has a value that is on one side of its baseline and is considered indicative of a break.

[0040] Another aspect of the invention is a sensor that defines a circuit for detecting breaks in a coating having a variable contour, which includes a generator with an electrical reference and a contact that receives current from the generator. The contact is adapted to move over areas of the coating spaced from the electrical reference of the generator while the generator sends current to the contact, where the contact adapts to the variable contours of the areas of the coating.

[0041] In one form of this aspect of the invention, the contact is a flexible conductive sheet.

[0042] In another form of this aspect of the invention, the contact is a flexible chainmail.

[0043] In another form of this aspect of the invention, the contact includes a carriage that rolls on guide wheels, a flexible conductor cable supported between the guide wheels, and a plurality of conductor rollers spaced along the cable, wherein each roller can rotate around the cable.

[0044] Other objects, features and advantages of the invention will become apparent from a review of the complete specification, including the claims and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is an illustration of a prior art sensor used to detect breaks in a coating;

[0046] Figure 2 is an illustration of an electrode brush used with prior art sensors, such as ΙνΙΛ / t / ZUZ4 / U 1 i / z and that of Figure 1;

[0047] Figure 3 is a cross-sectional illustration of a grounding plate and covering placed on the ground as used with prior art coverings and sensors, as illustrated in Fig. 1;

[0048] Figure 4 is an illustration of a new sensor described herein and used to detect breaks in a coating;

[0049] Figure 5 is an illustration of a new movable contact for sensors used to detect breaks in a coating;

[0050] Figures 6A and 6B are alternative moving contacts for sensors used to detect breaks in a coating;

[0051] Figure 7 is an illustration of an electromagnetic detector as it can be used with the sensor in Figure 4;

[0052] Figure 8 is an illustration of an alternative modality of a break sensor in which both current and voltage can be detected to determine the presence of a break;

[0053] Figure 9 illustrates a sample waveform of the detected current showing the threshold used with prior art sensors versus the threshold determined by the new sensors described herein; and

[0054] Figure 10 is a flowchart showing the operation of a new sensor such as the one described herein that measures both current and voltage amplitudes and uses these measured amplitudes to dynamically determine thresholds for each indication of the presence of a break. ML / C / ZUZ4 / U 1 1 zzy DETAILED DESCRIPTION

[0055] As described in detail below, a new apparatus and method for identifying coating breaks are described, including a generator having two contacts with a coating, with the generator pulses current to one of the moving contacts. The pulsed current is continuously processed to continuously generate a baseline indicative of a break. In addition, a plurality of detected electrical signals, such as current and voltage, can be processed so as to continuously generate baselines for each signal indicative of a break, wherein a break signal is triggered when any signal is detected which, compared to its generated baseline, indicates a break. The moving contact can be flexible to conform to the contour of the coating.

[0056] As further background to the description, Figs. 1-3 in this document provide further details regarding an apparatus of the prior art that improves upon the apparatus and method described herein.

[0057] Specifically, Figure 1 illustrates a detection apparatus that defines a circuit in which a high-voltage generator 10 has a first wire 12 connected to an electrode or grounding plate 14 and a second wire 16 connected to a movable electrode or conductive brush 20. In use, the apparatus's grounding plate 14 (i.e., an electrical reference, such as an earth) is connected to the top of the coating 24 being tested, and the brush of the electrode 20 is moved over areas of the coating 24. The generator 10 has provided a constant current or, in some versions, has generated high-voltage pulses.

[0058] The grounding plate 14 serves as a capacitive plate to couple electrical power to the sheathing 24. However, it should be understood that in some applications the grounding plate 14 could be placed on the ground and not on the sheathing 24 (i.e., the grounding plate 14 could be placed on the ground or grounded outside the limits of the sheathing 24). ML,A. ζυζΐυΐ i / ¿y

[0059] The brush 20 is normally made of metal bristles 22 that form an electrode to impart high voltage to the coating 24, where a break is generated. A non-conductive handle 26 is attached to the brush 20 and allows the user to sweep the brush 20 across the coating 24 for testing. However, as illustrated in Fig. 2, the stiff bristles of the brush 20 have been susceptible to variations in contact with the coating 24, particularly when the coating contour is not flat.

[0060] As illustrated in Fig. 3, the linings 24, such as geomembranes, are normally located on the ground 28 and are intended to be watertight, with an insulating top layer 30 and a conductive bottom layer 32. The circuit of the apparatus will flow from the brush 20 through the lining 24 to the grounding plate 14. It should be appreciated that such current flow will be affected if the brush 20 comes into contact with an area of ​​the lining 24 that has a break, for instead of being limited to flowing along the insulating top layer 30, the current may flow through the break and then along the conductive bottom layer 32.

[0061] Such prior art devices have included a detector 40 in the circuit for detecting current flow and a comparator 42 that compares the signal with a threshold considered indicative of a break. For example, if the current intensity rises to a value above the threshold, this would be taken as an indication of a break (i.e., where the intensity of the increase indicates flow through the lower conductive layer of the cladding). However, as noted above, while a spike in current flow could be indicative of a break, it could also result from other factors, such as instantaneous variations in the current or voltage imparted to the electrodes and changes in the earth conductivity of the soil beneath the cladding (depending, for example, on the soil type and moisture).Other factors could include, for example, abrupt changes in the movement of brush 20 and / or abrupt changes in the degree of contact between brush 20 and coating 24.

[0062] The threshold used by comparator 42 has been manually set, either based on operator experience or by initially testing the current intensity in areas known to be free of breaks and / or where breaks are known to exist. Once the test begins, the threshold is set for the entire area being tested, although the operator can manually change the threshold if it is determined that the threshold is inappropriately producing false positives (indicating a break where none exists) or false negatives (failing to recognize a break where one exists).

[0063] An audible alarm 44 has alerted the operator when the detected electrical signal exceeds the threshold, indicating that brush 20 is located in a break.

[0064] The improved apparatus and method described herein are illustrated beginning with Fig. 4. That is, as illustrated in Fig. 4 and described in more detail below, the sensor 100 for identifying breaks in coatings 124 includes an improved movable electrode or contact 120 that maintains uniform contact with coatings 124 of uneven contour. Furthermore, as also illustrated and described in more detail below, a high-voltage generator 110 generates a signal that is advantageously processed in the sensor 100 in a manner that greatly reduces false positives and false negatives.

[0065] Specifically, as shown in Figs. 4-5, the moving contact 120 includes a carriage 130 that rolls on guide wheels 132 with a flexible conductor cable 134 supported between the guide wheels 132. A plurality of conductor rollers 136 are spaced along the cable 134, each roller 136 being able to rotate around the cable 134. As illustrated, given the flexibility of the cable 134, all rollers 136 will make contact with the sheathing 124 even in areas that are not flat but have contours. ΜΛ / t / ZUZ4 / U 1 1 / zy rolling.

[0066] Still other variations for the moving contact include materials that are flexible, conformable to the surface and conductive, such as the chainmail 120A illustrated in Fig. 6A and a flexible conductive film 120B (e.g., conductive neoprene) illustrated in Fig. 6B that can be dragged through the cladding 124.

[0067] Furthermore, with reference to Fig. 4 and the improvement described herein, the sensor 100 also includes a break detector unit 150 which includes a high voltage generator 110. In addition, the high voltage generator can be a high voltage pulse generator 110A (see Fig. 7) by means of which the break detector unit 150A can advantageously determine the baseline break measurement dynamically as discussed in more detail below.

[0068] With reference now to Fig. 8, the detector unit 150 in another aspect of the invention may advantageously include an electromagnetic detector 152 (see Fig. 7) that detects not only the current traveling through the high-voltage cable 116 but also the energy (voltage and current) from the high-voltage generator 110. An electromagnetic detector 152 is more sensitive than the current detectors used in prior art systems and is therefore less susceptible to false positive and false negative signals.

[0069] Furthermore, an electromagnetic detector 152, as illustrated in Figure 8, can be advantageously used with a high-voltage pulse generator 110A. The electromagnetic detector 152 is a combination of a magnetic (inductive) coupler 154 and an electrical (capacitive) coupler 156 that detects the energy variation occurring in the high-voltage pulse generator 110A. The electromagnetic detector 152 is sensitive to changes in the current flowing in the high-voltage cable 116 and to changes in the electrical charge between the electrode (e.g., Figs. 5, 6A, 6B) and the cladding 124. A processor 160 compares the detected signals with thresholds for each signal (e.g., current and voltage) that are considered indicative of a break.

[0070] (Generally, a spike in a signal, such as a spark, that causes the current intensity to exceed a threshold or baseline, would be indicative of a break. However, it should be understood that for different signals, a signal falling below a threshold may indicate a break. As such, while the invention may sometimes refer generically herein to exceeding or surpassing a baseline or threshold in reference to the detection of a break, more precisely when referring to a signal indicating a break based on the signal relative to its baseline or threshold, a break is to be said to be detected when the signal intensity has a value that is on one side of its baseline or threshold [i.e., above or below] that is considered indicative of a break.)

[0071] Furthermore, the electromagnetic detector 152 can advantageously measure changes in both current and voltage by coupling to the high-voltage cable 116 through a winding and toroid 162 of an inductive coupler 154 and through conductive plates 164 of an electrical (capacitive) coupler 156. Fig. 8 illustrates such a sensor 100 in which an inductive coupler 154 with a winding toroid 162 is used to detect current in the high-voltage cable 116, and an electrical coupler 156 with conductive plates 164 is used to detect voltage. By detecting changes in both current (by measuring the magnetic field) and electric field over time, the sensor 100 can detect smaller fluctuations and is more sensitive to small breaks than sensors of the prior art.For example, by comparing each of a plurality of signals to its own separate baseline, a break can be detected in cases where only one of the signals exceeds its baseline (e.g., in cases where a break may cause a minor change in current but cause a significant and noticeable change in the electric field).

[0072] Therefore, it must be recognized that the described sensor 100 measuring a plurality of signals (e.g., current and voltage, rather than current alone) can advantageously minimize false positive and false positive signals.

[0073] An additional advantageous feature of the described sensor 100 is the dynamic determination of the threshold(s) of the monitored signal(s), calculated continuously by the processor 160. In this regard, the sensor 100 includes a high-voltage pulse generator 110A, with the break detector unit 150 continuously detecting a plurality of at least one electrical signal associated with the pulsating current. The processor 160 continuously processes the plurality of each type of signal (e.g., current or voltage) detected during a recently selected time period (e.g., 30 pulses per second for one second) and continuously generates and updates a dynamic baseline or threshold for each type of detected signal. Such baselines can be determined using the signals from the recently selected time period by a suitable method, such as energy averaging, filtering, and Fourier spectroscopy.

[0074] Figure 9 illustrates this function in comparison with prior art sensors where the thresholds were manually adjustable but otherwise fixed. In the illustrated example, it can be seen that while the fixed threshold of the prior art is a flat line 180, the dynamic, self-adjusting threshold 182 will change given the environmental changes encountered by the moving contact 120 (e.g., different soil resistivity in the area of ​​the moving contact 120 and / or movement of the moving contact 120). Therefore, in the prior art, a peak 186 exceeding the prior art flat line threshold 180 would be considered to indicate (falsely) a break at the location of the moving contact 120, even though the peak 186 may result from environmental factors in the area of ​​the moving contact 120 and not a break.Conversely, with the sensor 100 described herein, the processor 160 will dynamically incorporate such factors to create a self-correcting dynamic threshold 182 so that the comparison of the signal to the threshold will take into account environmental factors to avoid false positive signals. Similarly, when environmental factors would cause a reduction in the signal, the processor 160 as described herein will result in a reduced threshold (or a threshold drop) and avoid false negative signals.

[0075] Fig. 10 is a flowchart showing the method of operation of sensor 100 described herein with dynamic threshold determination and detection of multiple different signals.

[0076] Specifically, sensor 100 is first turned on (step 200) and the high-voltage pulse generator 110A is charged (step 202). A high-voltage pulse is discharged through the high-voltage cable 116 to the moving contact 120 (step 204), and the electromagnetic detector 150A of the break detection unit 150 acquires the current and voltage amplitude (step 206) of that pulse, which the processor 160 uses to calculate the average signal strength indicative of a break (step 208). In step 210, the processor 160 uses the signal strength calculated from step 208 to calculate a detection threshold relative to the electrical reference (e.g., ground 14) of the generator 110. The high-voltage pulse generator 110A is recharged (step 212) and a pulse discharged to the moving contact 120 (step 214), the electromagnetic detector 150A of the break detector unit 150 acquiring the current and voltage amplitude (step 216) of that pulse.This process of repeatedly discharging a high-voltage pulse, which the electromagnetic detector 150A detects and the processor 160 uses to update the dynamic threshold, is repeated over and over until a certain amount of pulse data has been acquired, at which point another pulse is added to the data. The data for the oldest pulse is excluded from the average calculated in step 208. The operation then continues in this manner until the processor 160 determines that a pulse has exceeded the current calculated detection threshold (e.g., current amplitude and / or voltage), in which case an alarm or location indicator 144 is sent.

[0077] Advantageously, sensor 100 can enable the operator to control the high voltage pulses as described above by pressing a suitable trigger switch when such a pulse is desired (in step 200 initially, and later in step 212 when sufficient data has been acquired).

[0078] The location indicator 144 may be a conventional audible alarm included with the break detection unit 150 that sounds when a break is detected (the sound thus alerting the operator that a break is present at the location of the moving contact 120), and / or may include any suitable signal, including visual signals (e.g., a light) or a digital signal that marks the location of the moving contact 120 (and thus the break) on the grid.

[0079] With an understanding of the above description, it should be recognized that the detection of breaks in linings (e.g., geomembranes) can be achieved advantageously, easily, and reliably, with minimal indications of false positives and / or false negatives.

Claims

1. A method for detecting breaks in a coating, comprising the steps of: creating a circuit for current from a generator to a first contact with said coating to a second contact spaced from said first contact to said generator, said second contact being an electrical reference for said generator; pulsing current from said generator to said first contact of the coating as said first contact moves over said coating; detecting a plurality of at least one electrical signal associated with said pulsing current from said electrical reference;continuously processing a selected plurality of said detected electrical signals to generate a reference value for said at least one electrical signal, wherein a detected electrical signal having a value on one side of the baseline is considered to indicate no breakage and an electrical signal having a value on the other side of the baseline is considered to indicate a breakage; and actuating a breakage signal when at least one of said detected electrical signals has a value on said other side of said baseline; 2. The method according to claim 1, wherein said second contact is with the top of said coating.

3. The method according to claim 1, wherein said second contact is with the ground beneath said coating.

4. The method of claim 1, wherein: said coating has an upper surface and a lower surface; said lower surface of the coating is electrically conductive; and said first and second contacts are in contact with said upper surface of the coating.

5. The method according to claim 4, wherein said liner is a geomembrane at a geotechnical site.

6. The method according to claim 5, wherein said geomembrane comprises a plurality of liners joined together by seams.

7. The method according to claim 1, wherein said at least one electrical signal is one selected from current intensity and voltage.

8. The method according to claim 1, wherein said at least one electrical signal comprises both current and voltage, wherein said detected current is continuously processed to generate a current baseline and said detected voltage is continuously processed to generate a voltage baseline.

9. The method according to claim 8, wherein said break signal is generated when any of said current or voltage intensity passes its generated baseline.

10. The method according to claim 1, wherein at least one of energy averaging, filtering and Fourier spectrum is used to generate the baseline from the recent plurality of detected electrical signals.

11. The method according to claim 1, wherein said baseline is a selected average of the recent plurality of detected electrical signals.

12. The method according to claim 1, wherein said activated break signal is at least one of an audible sound and a warning light.

13. The method according to claim 1, wherein said activated break signal is a location indication corresponding to the area of ​​the coating that is being contacted by the first contact at the time the detected electrical signal has a value on the other side of the baseline.

14. The method according to claim 13, wherein said activated break signal is at least one of a grid coordinate signal on the coating, an audio signal, a visual signal and a GPS coordinate signal.

15. A sensor for detecting breaks in a coating, comprising: a pulsed generator with electrical reference; an electrode adapted to move and maintain contact with the coating spaced apart from said generator's electrical reference while said generator delivers current to said electrode; a processor adapted to detect over time from said generator's electrical reference at least one electrical signal associated with said pulsed current, continuously process for a recent selected period of time the at least one detected electrical signal during said selected period of time, and generate a baseline of said at least one electrical signal, wherein a detected electrical signal having a value on one side of the baseline is considered to indicate no breaks and an electrical signal having a value on the other side of the baseline is considered to be Μλ,ΐ.ζυζΐυΐ i / y indicates a break; and a break signal is activated when any detected electrical signal has a value on said other side of said baseline.

16. The sensor according to claim 15, wherein said electrical reference can be placed on said coating.

17. The sensor according to claim 15, wherein said processor is adapted to detect one selected from current intensity and voltage.

18. The sensor of claim 15, wherein said processor is adapted to: detect both the current intensity and the voltage; continuously process the current intensity to generate a current intensity baseline; and continuously process the voltage to generate a voltage baseline.

19. The sensor according to claim 18, wherein said break signal is activated when either of said detected current intensity or detected voltage is on the other side of its generated baseline.

20. The sensor according to claim 15, wherein said processor is adapted to use at least one of energy averaging, filtering and Fourier spectrum to generate the baseline from the recent plurality of detected electrical signals.

21. The sensor according to claim 15, wherein said activated break signal is at least one of an audible sound and a warning light.

22. The sensor according to claim 15, wherein said break signal is a location indication corresponding to the area of ​​the coating that is in contact with the electrode at the time when the value of the detected electrical signal is on said other side of said baseline.

23. A method for detecting breaks in a liner, comprising the steps of: creating a circuit for current from a generator to a first contact with said liner to a second contact spaced from said first contact to said generator, said second contact being an electrical reference for said generator; sending current from said generator to said first contact of the liner when said first contact moves over said liner; detecting current and voltage at said generator electrical reference; comparing a baseline current to the current at said generator electrical reference; comparing a baseline voltage to the voltage at said generator electrical reference;and activating a break signal activated when either of said current or voltage intensity has a value that is on one side of its baseline that is considered to indicate a break; 24. The method according to claim 23, wherein: said coating has an upper surface and a lower surface; and said lower surface of the coating is electrically conductive.

25. The method according to claim 24, wherein said first and second contacts are in contact with said upper surface of the coating.

26. The method according to claim 23, wherein said liner is a cheomembrane at a geotechnical site.

27. The method according to claim 25, wherein said geomembrane comprises a plurality of liners joined together by seams.

28. The method according to claim 23, wherein said detected current intensity is continuously processed to generate said current intensity baseline and said detected voltage is continuously processed to generate said voltage baseline.

29. The method according to claim 23, wherein said break signal is generated when any of said current or voltage intensity passes its generated baseline.

30. The method according to claim 23, wherein at least one of energy averaging, filtering and Fourier spectrum is used to generate the baseline from the recent plurality of detected electrical signals.

31. The method according to claim 23, wherein said baseline is a selected average of the recent plurality of detected electrical signals.

32. The method according to claim 23, wherein said activated break signal is at least one of an audible sound and a warning light.

33. The method according to claim 23, wherein said activated break signal is a location indication corresponding to the area of ​​the coating that is in contact with the first contact at the time when said current intensity has a value on said side of the current intensity baseline considered to indicate a break, or said voltage has a value on said side of the voltage baseline that is considered to indicate a break.

34. A sensor for detecting breaks in a liner, comprising: a generator with an electrical reference positionable on or adjacent to said liner; an electrode adapted to move and maintain contact with the liner away from said generator electrical reference while said generator outputs current to said electrode; a detector that detects current at said generator electrical reference and voltage at said generator electrical reference; and a processor adapted to compare a baseline current to the current at said generator electrical reference and compare a baseline voltage to the voltage at said generator electrical reference;and a break signal activated when said detected current intensity has a value that is on one side of its baseline current intensity considered indicative of a break or said detected voltage has a value that is on one side of its baseline voltage considered indicative of a break; 35. The sensor of claim 34, wherein said processor is adapted to: continuously process the current intensity to generate said baseline current intensity; and continuously process the voltage to generate said baseline voltage.

36. The sensor according to claim 35, wherein said processor is adapted to use at least one of energy averaging, filtering and Fourier spectrum to generate the baseline from the recent plurality of detected electrical signals.

37. The sensor according to claim 35, wherein said break signal is activated when either of said detected current intensity or detected voltage is on the side of its generated baseline that is considered indicative of a break.

38. The sensor according to claim 34, wherein said activated break signal is at least one of an audible sound and a warning light.

39. The sensor according to claim 34, wherein said break signal is a location indication corresponding to the area of ​​the coating that is in contact with the electrode when the detector detects at least one of current and voltage intensity having a value that is on one side of its baseline considered indicative of breaks.

40. A sensor defining a circuit for detecting breaks in a coating having a variable contour, comprising: an electrically referenced generator; and a contact receiving current from said generator and adapted to move over areas of said coating spaced from said generator's electrical reference while said generator sends current to said contact, wherein said contact adapts to the varying contours of said coating areas.

41. The sensor according to claim 40, wherein said contact is a flexible conductive sheet.

42. The sensor according to claim 40, wherein said contact is a flexible mesh.

43. The sensor of claim 40, wherein said contact comprises: a carriage rolling on guide wheels; a flexible conductive cable supported between said guide wheels; and a plurality of conductive rollers spaced along said cable, each roller being rotatable about said cable.

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