DE102015108233A1 - Method and device for identifying faulty conductors - Google Patents

Abstract

The present invention relates to a method and apparatus (100) for identifying faulty conductors (18) in a conductor arrangement (10) having at least two conductors (11) connected in parallel by applying a voltage UAC to the conductor arrangement (10) around a magnetic field (15, 17), measuring a field strength H of the magnetic field (15, 17) along a transverse direction x of the conductor arrangement (10) and evaluating an amplitude of the measured field strength. The method can be used, for example, to identify defective conductor arrangements (10) for electrically heatable disks (50).

Description

The present invention relates to a method and apparatus for identifying faulty conductors in a parallel-connected conductor arrangement.

Parallel conductor arrangements are often used for surface heating of objects. Known applications of such conductor arrangements are for example heated front and rear windows, hot plates, electric blankets and the like. In heated front and rear windows substantially parallel and parallel conductors are mounted in or on the disc to eliminate any glaciation or fogging occurring due to heating of the disc. For this purpose, a DC voltage, in motor vehicles usually 12 V, applied to the conductor arrangement.

Each of the conductors has a certain electrical resistance R. The electrical resistance R relates an applied voltage U and a resulting electric current I into the ratio. Each electrical resistance R converts electrical energy E _{el of} a current flow into heat energy, the so-called Joule heat Q _W. The electric energy E _{el is} calculated from the output electric power P _el and time t during which an electric current flows. The Joule heat Q _W consequently depends quadratically on the applied voltage U or the electrical current I and the electrical resistance R of the conductor, as well as the time t during which an electric current flows.

In ladder arrangements with thin conductors and small distances between the conductors, such. As in heated front and rear windows, it may come in a production to Kontaktierungsfehlern or cable breaks in the ladder. The finished disc is then not heated in the area of contact failure or cable breakage. With iced slices, this leads to uneven defrosting, which delays the entire defrosting process and leads to visual impairments.

Consequently, it is necessary to check the proper functioning of the conductor arrangement at the end of the production in order to be able to anticipate the aforementioned defects and to sort out defective conductor arrangements. In this case, for example, a thermographic analysis of the conductor arrangements, especially with thin conductors at a small distance from each other is not possible because the resolution of such analyzes is too low to detect individual faulty conductors can. In addition, conductor arrangements with sensitive conductors can be acted upon only with low measuring voltages, because a burning through of the sensitive conductors is imminent. Consequently, a control and in particular an identification of faulty conductors, especially for conductor arrangements with a small distance between the individual conductors and with small conductor diameters, or sensitive conductors, such. B. for heated discs, not known in the art.

On this basis, it is an object of the present invention to solve the problems of the prior art, in particular for conductor arrangements with sensitive conductors, such as conductor arrangements for heated disks, or at least alleviate. The present invention proposes for this purpose a method and a corresponding device for the identification of faulty conductors in parallel conductor assemblies, and a method for producing a heatable disk, wherein the method according to claim 1 and the corresponding apparatus and method for producing according to the independent claims fix or at least mitigate previously identified issues. Further embodiments of the present invention are listed in the subclaims. The description, in particular also in connection with the figures, explains the invention and provides further embodiments.

• a) Anlegen einer Spannung, U_AC an die Leiteranordnung, um ein magnetisches Feld zu erzeugen.
• b) Messen einer Feldstärke, H des magnetischen Felds entlang einer Querrichtung x der Leiteranordnung.
• c) Auswerten einer Amplitude der gemessenen Feldstärke, um fehlerhafte Leiter zu identifizieren.

The method proposed here for identifying faulty conductors in a conductor arrangement with at least two conductors connected in parallel comprises at least the following steps:

• a) Apply a voltage, U _AC to the conductor arrangement to generate a magnetic field.
• b) measuring a field strength, H of the magnetic field along a transverse direction x of the conductor arrangement.
• c) evaluating an amplitude of the measured field strength to identify faulty conductors.

The method is used in conductor arrangements of two or more conductors connected in parallel. A conductor may be a wire, a conductive coating or a similar element. As a material for a conductor, an electrically conductive substance such as a metal (copper, gold, aluminum, iron, platinum, silver, etc.), a metal alloy (red brass, etc.), a highly doped semiconductor u. Ä. Serve. A conductor can have a uniform diameter over its entire length. The diameter can be in the micrometer range. The conductors may be substantially parallel to each other. It means in parallel that the vertical distance between the conductors, that is, the perpendicular from one conductor to the adjacent one, is substantially the same at each point, even if the conductors follow a curved path. A conductor may be sawtooth, helical, helical or similar in a longitudinal direction y. The longitudinal direction y therefore describes the direction along a main extension direction of the individual conductors. The conductors may have a distance in the millimeter range to each other. The distance between the individual conductors can be different.

The conductor arrangement can have a quasi-two-dimensional (2.5 D) structure, so that the conductors can run in an arbitrarily curved plane. The conductors can either be self-supporting and / or fixed by a frame and / or a carrier structure, wherein the conductors can run on and / or within the carrier structure. The support structure may be formed of at least one material of the following group: glass, laminated glass, polymer, ceramic, composite material, textile and another electrically electrically conductive material. For the generation of Joule heat Q _W , a DC voltage can be applied to the conductor arrangement, the voltage being less than 100 V [volts], preferably less than 50 V [volts] and more preferably 5 V [volts] - 15 V [volts ] is big. For heated windows of motor vehicles a DC voltage of 12 V [Volt] or 48 V [Volt] is provided.

To generate a magnetic field around the individual conductors, a voltage U _{AC can be applied} to the conductor arrangement. The voltage U _AC can be sinusoidal, sawtooth, rectangular, pulse-like or comparable alternating. However, a continuous, linear, quadratic, cubic, exponential or comparable variable course of the applied voltage is possible. An amplitude U _{0 of} the voltage U _AC may have a positive or negative offset. A current I _AC through the conductors is calculated as:

A magnetic field strength H _{i of} a radial magnetic field that forms around each of the i conductors due to the current flow is calculated (for a straight conductor) via the electrical current I _AC and the distance r from a longitudinal axis through the conductor.

The magnetic field strength is constant on each concentric circular path at a distance r (from a minimum distance) around the conductor. The individual magnetic fields of the respective conductors overlap to form an overall magnetic field of the conductor arrangement. Lines of equal field strength H _{tot of} the total field are substantially elliptical, with the isometric lines across the conductor arrangement being substantially parallel to a surface spanned by the longitudinal direction y and a transverse direction x of the conductor arrangement. In this case, the transverse direction x of the conductor arrangement is perpendicular to the longitudinal direction y of the conductor arrangement, ie perpendicular to the direction in which the individual conductors extend or their longitudinal axis.

Depending on the application and in the immediate vicinity, the magnetic field strength can vary significantly. Close to the conductors (eg in a range of 0.5 to 2.0 mm [millimeters], but dependent on the strip conductor spacing), the magnetic field may still have a strong modulation, which may also be detected. Deviations from the expected modulation can also be used to infer faulty conductors.

With a sensor, the local field strength H can be measured. In addition, the field strength H along the transverse direction x of the conductor arrangement can be measured by displacing the sensor along said transverse direction x. In this case, the field strength H or a measured variable representing it is recorded or even recorded relative to a feed s in the transverse direction x. The field strength H _{ges of} the total magnetic field of the conductor arrangement can therefore be measured relative to the feed s with the moving sensor. Each sensor has a measuring direction or measuring surface, which in a certain way is to be aligned with the quantity to be measured, in this case the field strength H _ges .

The measured field strength H or the representing measured variable is evaluated with respect to its amplitude. Decreased amplitudes indicate a conductor which does not conduct current. A conductor may be de-energized due to a bonding fault or a wire / cable break and therefore no generate magnetic field. It is also possible that a conductor, if it is a coating, has a smaller (or larger) layer thickness and therefore a higher (or lower) resistance R. This in turn leads to a smaller (or larger) current I _AC than intended, which is reflected in a lower (or larger) field strength H _i . Thus, such defective conductors contribute no or an altered magnetic field strength H _i to the overall magnetic field. The isometric lines of the field strength H _{tot of} the total magnetic field of the conductor arrangement are therefore not parallel to the conductor arrangement via faulty conductors, but towards it (with no or low current I _AC through the faulty conductor) or away from it (with larger current I _AC through the faulty conductor). There are virtually dents in the total field over faulty ladders. Therefore, the measured field strength H in the region of defective conductors has a reduced (or increased) amplitude when advancing along the transverse direction x to the conductor arrangement. If several adjacent conductors are faulty, the distortion of the field strength H _{ges of} the total magnetic field of the conductor arrangement there is correspondingly even greater than in the case of a single faulty conductor. As the number of adjacent faulty conductors increases, the distortion of the overall magnetic field of the conductor assembly becomes larger and larger, with the largest distortion always in the middle of the adjacent faulty leads-above one odd-numbered conductor and between two conductors even-numbered defective conductors. Consequently, a conclusion can be drawn on faulty conductors due to fluctuations in the amplitude of the measured field strength H or the measured variable representing the field strength H, and thus defective conductor arrangements can be identified. When the conductors are made as a coating, variance in the coating of individual conductors that results in a reduced (or increased) current flow can also be identified by the resulting lower (or increased) field strength H _{ges of} the magnetic field. The measured variable is subject to fluctuations and noise due to environmental influences from the environment. Therefore, an upper limit and a lower limit should be set, between which fluctuations are considered to be caused by the environment and are not due to faulty conductors. If the measured amplitude is above or below the upper limit, one or more faulty conductors shall be assumed. The two limit values can be determined and stored by simple experiments with faultless conductor arrangements under stationary conditions.

Additionally or alternatively, the modulation of the magnetic field may also be analyzed, with, for example, a singularity (eg, a salient peak) indicating a faulty conductor.

The proposed method for identifying faulty conductors in a conductor arrangement can quickly and reliably identify a defective conductor arrangement or faulty conductors which cause a changed or no current I _{AC as} a result of contact errors or conductor / cable break or variations in the layer thickness , Thus, defective conductor arrangements can be sorted out selectively, so that the quality of the supplied conductor tracks increases. The conductor assemblies sorted out as defective can then be recycled and fed back into the manufacturing process for conductor arrangements. In addition, with the proposed method, even the location of a minimum magnetic field strength H _min or a maximum field strength H _max can be very accurately localized by means of the greatest distortion of the measured field strength H or of the corresponding measured variable when advancing the coil via the conductor arrangement. This way, the faulty ladder (s) can be tracked. On the one hand, this increases, as already mentioned, the quality of the conductor arrangements and, on the other hand, faulty conductor arrangements do not have to be completely dismantled and recycled, but can be repaired or reworked in a targeted and cost-effective manner.

The method is preferred when a diameter of the conductors is less than 100 μm [microns]. The conductors of the conductor arrangement, which are checked by the method, can have a diameter in the micrometer range. The diameter of the conductors is preferably less than 100 μm [micrometers] and more preferably between 1 μm [micrometers] to 30 μm [micrometers]. The smaller the diameter of the conductors, the greater their electrical resistance R and thus the Joule heat, which is generated when a DC voltage is applied. This is advantageous in conductor arrangements which serve as a heat source. The method can also identify faulty conductors with a diameter of a few micrometers and a particularly low current I _AC .

The method is particularly suitable for conductor arrangements in which the distance between the individual conductors is less than 10 mm [millimeters]. The distance between adjacent conductors of a conductor arrangement can be only a few millimeters. The distance is preferably less than 10 mm and more preferably between 0.1 mm and 3 mm. In the case of conductor arrangements which serve as a heat source, the heat released per unit area can be achieved by a short distance between the individual conductors increase. The method can also be used to identify defective conductors in conductor arrangements with a small spacing between adjacent conductors, that is to say with high spatial resolution.

In one embodiment of the proposed method, the voltage U _AC applied in step a) has an amplitude U ₀ of less than 10 V [volts]. The voltage U _AC applied in step a) may be limited to a specific value in its amplitude U ₀ and / or in its effective value U _eff . The voltage U _AC preferably has an amplitude U ₀ of less than 10 V [volts] and particularly preferably an amplitude U ₀ of 0.25 V [volts] to 2 V [volts] or preferably an effective value U _eff of less than 15 V. [Volt] and more preferably an effective value U _eff of 0.375 V [volts] to 3 V [volts]. The individual conductors of the conductor arrangement, especially if they have small diameters in the micrometer range, can easily burn out if an excessively high amplitude U ₀ or effective value U _eff . To avoid this, the applied voltage U _AC must be adapted to the dimensions of the conductors. This can prevent damage to the conductors during the identification of faulty conductors.

In one embodiment of the method according to the invention, the field strength is measured in step b) via an induction voltage U _ind . Especially conductors with a diameter in the micrometer range have a high resistance R. The applied voltage U _AC can not be selected high for conductors with a small cross-section, since otherwise there is a risk of burn-through of the conductors. Therefore, in such a case, the induced current I _AC and the resulting magnetic field intensity H _i around the individual conductors is small. Low field strengths H _ges can be measured via an induction voltage U _ind by magnetic induction in a coil with the method, an alternating voltage being used as the applied voltage U _AC . It is also possible to choose a voltage U _AC with a different time-varying course (exponential, quadratic, cubic, etc. increasing / decreasing). A magnetic flux density B _ges is linked to the magnetic field strength H _{ges of} the conductor arrangement via the magnetic permeability μ of the flooded substance. B _tot = _tot .mu.H

A magnetic flux φ through an area A _{ind of} the coil is calculated by: φ = ∫B _ges dA _ind

The induction voltage U _ind depends on the change in the magnetic flux φ with time t. U _ind = ∂φ / ∂t

If the total magnetic field of the conductor arrangement with the flux density B _{tot is} perpendicular to the coil surface A _ind , the voltage U _ind induced in the coil is calculated via:

Since the magnitude and the sign of the AC voltage U _AC (U _AC (t) ≠ const.) And thus also the magnetic flux density B _{ges change} with time, the first derivative term is retained. The second derivative term is not preserved, provided that the coil is not tilted with respect to its displacement direction, ie the transverse direction x of the conductor arrangement, and the area A _ind flooded by the magnetic field does not change over time.

If the coil surface A _{ind is} not perpendicular to the direction of the magnetic field, the resulting induction voltage U _{ind is} not maximal. In such a case, the deviation angle enters the equation via a (constant) sinusoid. The coil can be moved in the direction of its surface normal perpendicular to the longitudinal axis of the conductors, ie in the transverse direction x of the conductor arrangement, and perpendicular to the surface normal of the conductor arrangement with a certain distance over the conductor arrangement. In this way, the induction voltage U _{ind is} induced with the maximum possible amplitude. The amplitude of the induction voltage U _ind directly over the individual conductors of the conductor arrangement, and also in the areas between, approximately the same size, as overlap the individual magnetic fields of the conductors and a form almost homogeneous magnetic field over the entire conductor arrangement. Since the induction voltage U _ind calculated over the time derivative of the AC voltage U _AC , the profile of the induction voltage U _ind z. For example, for a sinusoidal AC voltage U _AC = U ₀ sin (2πft) cosinusoid U _ind ~ cos (2πft) (or shifted by π / 2 and sinusoidal). Likewise, for different AC voltages U _AC, the respective induction voltages U _ind result from temporal differentiation. If the induction voltage U _{ind is} observed while the coil is moved over the conductor arrangement, as described above, then the profile of the induction voltage U _{ind has} a phase-shifted curve through 90 ° to a sinusoidal alternating voltage U _AC , the amplitude of the induction voltage U _ind while moving remains almost constant. If a conductor of the conductor arrangement does not conduct an electric current I _AC , even though an AC voltage U _AC is present, then there is either a contact failure or a conductor break or cable break or an excessively thin layer thickness or another fault. This faulty conductor thus produces no or a reduced magnetic field H _i . The overall magnetic field of the conductor arrangement thus has a lower field strength H _ges (dimple) in the vicinity of the defective conductor, the total magnetic field having directly above the faulty conductor the lowest field strength H _min in the feed direction x. The isometric lines of field strength H _tot are distorted over the faulty conductor in the direction of the conductor arrangement. Accordingly, the induction voltage U _ind when advancing the coil from the beginning of the fall of the magnetic field in the feed direction x to its lowest field strength H _{min has} a nearly constant decreasing amplitude. In the region in which the magnetic field of the conductor arrangement increases again, the induction voltage U _{ind has} an increasing amplitude when the coil is advanced. Thus, a faulty conductor arrangement can be detected by a fluctuation in the amplitude of the induction voltage U _ind .

If the coil is moved in the direction of its surface normal perpendicular to the longitudinal axis of the conductors, ie in the transverse direction x of the conductor arrangement, and perpendicular to the surface normal of the conductor arrangement, very close to the conductor arrangement (eg in a range of 0.5-2.0 mm), the magnetic field still shows a strong modulation that can be detected. Deviations from the expected modulation can equally (or even better) be used to refer back to faulty conductors. The amplitude modulation of the field strength H _ges has a lack of increase in the magnetic field, in particular over the faulty conductor.

After the production of conductor arrangements can therefore safely, quickly and inexpensively discovered and sorted out with the proposed method - even at low current I _AC through the conductor due to low applied amplitude U _{0 of} the voltage U _AC for protection against possible burn-through committee.

In one embodiment of the method according to the invention, the field strength is measured in step b) via a Hall voltage U _H. The field strength H _{ges of} the conductor arrangement can be determined via a Hall voltage U _H. Flows an electrical measuring current I _mess , ie charge carriers (electrons and / or holes) with an electrical charge q and a velocity v _mess , by a measuring sample, which of the magnetic field of the conductor arrangement in a direction not parallel to a flow direction of the current I _mess is traversed, then experience the charge carriers of the current I _mess perpendicular to the flow direction of the current I _mess and to the direction of the flow B _{ges of} the magnetic field, a Lorenz force F _L. F → _L = qv x B → _{measured ges}

By this Lorenzkraft so many charge carriers are deflected to an edge of the sample until they form an electric field that exerts a counterforce to the Lorentz force F _L , which is so large that the charge carriers are no longer deflected and the current I _mess unaffected the Test sample can happen. E _H = v _mess B _tot

The charge carrier shift can be tapped as Hall voltage U _H at the edge of the measurement sample and allows conclusions about the field strength H _{ges of} the magnetic field of the conductor arrangement.

Where d is the thickness of the sample and K _{H is} the Hall coefficient of the sample material. Preference is given to a semiconductor material with a high Hall coefficient for the test sample (low carrier density) used to obtain a high, easily measurable Hall voltage U _H. The resulting Hall voltage U _H is greatest when, with a constant field strength H _ges, the direction of the current I _{mess is} perpendicular to the direction of the magnetic field of the conductor arrangement.

Conductor arrangements can be investigated with the proposed method even for small field strengths H _{ges of} the magnetic field of the conductor arrangement on faulty conductors. Thus, defective conductor arrangements can be safely and quickly detected and sorted out. This increases the quality of the finished products, since no rejects leave the production.

In one embodiment of the method according to the invention, an alternating voltage with a frequency f of less than 10 MHz [megahertz] is applied as voltage U _AC in step a). The frequency f of the applied AC voltage U _AC can be in the kilohertz or megahertz range. The frequency f is preferably less than 10 MHz [megahertz] and more preferably between 100 kHz [kilohertz] to 1 MHz [megahertz]. The amplitude of the induction voltage U _ind increases with increasing frequency f despite increasing impedance of the conductors. Therefore, even with sinusoidal alternating voltages with low amplitude U _0, a measurable induction voltage U _ind can be generated. It should be noted that at frequencies f greater than 1 MHz, the amplitude of the induction voltage U _{ind can become} so large that disturbances of the measurement from the environment generate erroneous signals. By a suitable choice of the frequency f, highly sensitive voltage measuring devices can be dispensed with for measuring the induction voltage U _ind , so that the costs for the measuring device for carrying out the method according to the invention can be reduced.

In principle, it should be noted that the shape and shape of the conductors can also be different from the shape of a pane or the respective application. Thus, the conductors can differ in their length, bending, etc. from each other. For this reason, it may be useful to test only a specific portion of the length of the ladder metrologically. For this z. Example, to select a length range of up to 10 cm [centimeters], in particular a length range of 4 to 8 cm. This also increases the flexibility of the measuring system in order to test even smaller heating fields.

In an embodiment of the method, in step b) the field strength H is measured over at least 80% [percent] of a length of the conductor arrangement in the longitudinal direction y. If the field strength H _{ges of} the magnetic field of the conductor arrangement along the transverse direction x is detected over a larger measuring range in the longitudinal direction y, ie over a larger measuring area A _{ind of} the coil, the maximum value of the measured variable increases. A measurement range that extends substantially the full length, and preferably at least 80% [percent] of the length of a conductor of the conductor assembly thus provides a greater amplitude in the measurement. The amplitude of the measured induction voltage U _ind becomes larger and therefore more observable due to the increased area A _ind , which is penetrated by the magnetic field B. The resulting increased resolution of the measurements allows safer identification of faulty conductors in step c) because measurement inaccuracies are less significant as compared to the increased amplitude drops / slopes across faulty conductors. In this way, the accuracy of the method can be further increased. This leads to an even safer identification of defective conductor assemblies after the manufacturing process.

In one embodiment of the method, a measured variable is filtered in step b). The measured variable, which is measured to determine the field strength H _ges , can be freed of noise and interference by filters which are connected downstream of the sensitive element (coil or Hall sensor). For this purpose, a high-pass filter and / or a low-pass filter can be used which removes or attenuates frequencies which do not belong to a measuring signal of the sensor (in particular frequencies which do not correspond to the frequency of an impressed test signal). In this way, only amplitude fluctuations of the measured variable are taken into account in the identification of faulty conductors, which are based on fluctuations in the field strength H _ges and not noise or external interference with frequencies different from the frequency f of the applied voltage U _AC . This increases the reliability and robustness of the process against environmental influences.

In one embodiment of the method, in step b), the measurement takes place at a feed rate v _V of less than 20 cm / s [centimeter / second] along the conductor arrangement. The feed rate v _V with which the measurement of the field strength H _ges takes place along the transverse direction x of the conductor arrangement can be chosen such that fluctuations in the amplitude of the measured variable (U _ind or U _H ) clearly correspond to the frequency f or the feed rate and thus to the magnetic field of the conductor arrangement can be assigned. A fluctuation in the field strength H _{ges of} the magnetic field occurs between two adjacent conductors if one of the two conductors is faulty. This allows the frequency of a Fluctuation due to the advancement of the sensor via the conductor arrangement to be at most equal to the number of passed pairs of conductors per unit time. This can be calculated by the distance between the conductors d _L and the feed rate v _V.

Therefore, the feed rate v _{V is} always to be chosen so that the maximum possible frequency f _{V of} the fluctuations due to faulty conductors that have been run over, is smaller than the frequency f of the voltage U _AC . Analogous to the Nyquist-Shannon sampling theorem, the frequency f should be at least twice as large as the frequency f _V that can be generated by the feed. It is advantageous to choose a feed rate v _V which can produce a maximum frequency f _V which is orders of magnitude smaller than the frequency f. The feed rate v _V is preferably less than 20 cm / s and more preferably between 0.05 cm / s and 10 cm / s. By the method, a clear reconstruction of the amplitude curve of the measured variable and thus the field strength H _{ges of} the conductor arrangement along the feed s in the transverse direction x can be guaranteed.

In one embodiment of the method, the identification of faulty conductors is carried out iteratively. Step b) is performed at a first feed rate v ₁ . If a faulty conductor is identified in step c), an iterative return to step b) takes place, which is carried out again at a second feed rate v ₂ which is less than the first feed rate (v ₂ <v ₁ ). The field strength H _tot of each conductor arrangement can first be measured at an increased first feed rate v ₁ along the feed direction x. The first feed rate v ₁ is preferably 5 cm / s to 15 cm / s. Due to the increased feed speed, the spatial resolution of the measurement is reduced. Nevertheless, a faulty conductor can be detected in step c). If this is the case, step b) can be carried out again as part of an iteration. In this case, a lower second feed rate v ₂ can be used. The second feed rate v ₂ is preferably 0.1 cm / s to 4 cm / s. This increases the spatial resolution of the measurement and faulty conductors can be precisely located in step c). The smaller a distance between adjacent conductors of the conductor arrangement, the lower the feed rate v _{2 should be} selected in order to allow an exact localization. The iterative measuring and identification method proposed here is advantageous, because first of all a rapid measurement takes place and only in the presence of a fluctuation in the measured amplitude a more accurate measurement is carried out for accurate localization. This significantly reduces the time required for quality control. In addition, - even with small distances between adjacent conductors - a precise localization of faulty ladders done by the second feed rate v _{2 is} chosen sufficiently low. Instead of recycling defective conductor arrangements, they can be repaired and faulty conductors repaired or replaced in a targeted manner. This is faster and cheaper than a complete recycling of defective conductor assemblies. In one embodiment of the method, the iterative step b) takes place with the feed rate v ₂ only in areas in which a faulty conductor has been identified.

It is also possible to perform an additional additional measurement (at a different position in the longitudinal direction y) in order to verify faulty conductors.

In one embodiment of the method, a Fourier analysis is performed. The determined signal of the measured variable can be determined by a Fourier analysis, z. B. by a fast Fourier transform (FFT), to be analyzed in the frequency domain. Thereby, the strength of individual frequencies of the measurement signal within a time window .DELTA.t determined and thus the amplitude of the measured variable in a certain time interval with the appropriate frequency f of the voltage U _{AC are} determined. This in turn allows conclusions to be drawn about the field strength H _ges along the transverse direction x and thus makes it possible to identify faulty conductors. By a Fourier analysis, the automatic identification of faulty conductors can be done with little computational effort.

In one embodiment of the method according to the invention, the conductor arrangement is part of a heatable transparent pane for transportation means (such as, for example, a motor vehicle). The conductors of a heated disk conductor assembly for a locomotive means have a small diameter in the micrometer range to provide a high resistance R for generating Joule heat and not to obstruct the driver's vision. In addition, the conductors are arranged at a small distance in the millimeter range to each other to allow a high heat density. After an identification of faulty conductors with the method according to the invention, there are certainly no defective conductors in a tested conductor arrangement.

• A) Herstellen von Leiteranordnungen mit mindestens zwei parallelgeschalteten Leitern mit einem hohen elektrischen Widerstand;
• B) Identifizierung von fehlerhaften Leitern in den Leiteranordnungen mit dem Verfahren der vorstehend beschriebenen Art;
• C) Aussortieren von defekten Leiteranordnungen;
• D) Anbringen der Leiteranordnungen an Scheiben.

According to a further aspect, a method for producing a heatable pane is proposed which comprises at least the following steps:

• A) producing conductor arrangements with at least two parallel-connected conductors with a high electrical resistance;
• B) identifying faulty conductors in the conductor assemblies by the method of the type described above;
• C) sorting out defective conductor arrangements;
• D) Attach the conductor assemblies to disks.

A conductor arrangement with at least two parallel-connected conductors with a high electrical resistance can be done in various ways. It is possible to arrange and solder conductors in the form of wires to parallel structures or to apply electrically conductive coatings in the desired form to a carrier structure. The conductors can be connected in parallel via different circuits. The finished conductor arrangements are then checked with the method for identifying faulty conductors. If a defective conductor arrangement is detected, it is sorted out and then either recycled and fed back into the manufacturing process, or, if possible, repaired or repaired. The inspected (and eventually repaired / repaired) line assemblies are finally attached to a disk to provide heater functionality to the disk. The line arrangements can be mounted on a disk and / or introduced into a disk or pressed between two disk elements. With this manufacturing method heated disks can be produced in which the line assemblies have no faulty lines and thus no reduced or uneven heating. This increases the quality of the heated discs and can the price achievable for the heated disc, z. By granting a warranty on the heating functionality of the disc.

The likewise proposed device is set up to identify faulty conductors in a conductor arrangement having at least two conductors with a high electrical resistance connected in parallel. The device comprises a drive for generating an AC voltage U _AC and for applying said AC voltage U _AC to said conductor arrangement. Furthermore, the device comprises a sensor for determining a field strength H _{ges of} a magnetic field, resulting from said AC voltage U _AC along the transverse direction x of the conductor arrangement. In addition, the device comprises an evaluation device for evaluating an amplitude of a measured field strength H and for identifying faulty conductors.

In order to generate a measurable magnetic field around the individual conductors of the conductor arrangement, the voltage U _AC can be generated by a control. In this case, by means of a voltage source and an alternating voltage with the frequency f and the amplitude U _{0 can be} adjusted. The generated voltage U _AC can be connected via suitable connections such. As plugs, terminals and the like can be applied to the conductor arrangement.

By means of a sensor, the field strength H of a magnetic field, as already described above, are measured.

The evaluation device can detect the measured variable determined by the sensor, the feed rate s and / or the exact position of the sensor or conductor and analyze the amplitude of the measured variable. The evaluation device may comprise a voltage measuring device which detects the induction voltage U _ind or the Hall voltage U _{H of} the sensor. Since a reduction of the amplitude of the measured variable corresponds to a reduced field strength H _ges in the transverse direction x, a faulty conductor can be identified with a certain drop in the amplitude below a defined limit value. To this end, if the evaluation device comprises a digital processing device such as a microcontroller, an application-specific integrated circuit (ASIC), an application-specific standard product (ASSP), a field-programmable logic gate array (FPGA) and the like, an analog-to-digital Conversion (A / D) of the measured values. This can be done by a suitable A / D converter. For this purpose, the analog measuring signal is sampled (discretized) by the sensor or by the voltage measuring device at a certain sampling rate and, depending on the resolution of the A / D converter, converted into a sequence of binary variables (quantized). The digitized measurement signal can then be processed by digital circuits. The A / D converter may be a separate element or integrated in the evaluation device. It may be a Fourier analysis of the measurement signal, such. B. a fast Fourier transform (FFT) for the evaluation of the measured variable and identification of faulty ladders by the evaluation device.

In one embodiment of the device, the sensor comprises a coil for measuring an induction voltage U _ind . With the coil, the field strength H _{ges of} the magnetic field of the conductor arrangement via the induction voltage U _ind , as already described above, be determined. The coil may consist of one or more turns, the number of turns (turns) N being proportional to the induced voltage U _ind . U _ind = N dφ / dt

The larger the area A _{ind of} the coil, the greater is an inductance of the coil and thus the induced voltage U _ind .

Different geometric shapes of the coil surface A _{ind are} possible. It may be a circular, square, elliptical, rectangular or other form may be used, with an elongated rectangular shape is preferred. Different types of conductors, such as wires or printed conductors, can be used for the turns of the coil. The coil conductors can be made of an electrically conductive material, such as a metal (copper, gold, aluminum, iron, platinum, silver, etc.), a metal alloy (red brass, etc.), a highly doped semiconductor u. Ä. exist.

With the sensor according to the invention comprising a coil, even a low magnetic field strength H _ges due to a low applied voltage U _AC to protect the conductors from burning through a well-measured induction voltage U _ind for the identification of faulty conductors in the conductor arrangement can be measured. This increases the quality of the ladder arrangements provided.

In one embodiment of the device according to the invention, the sensor comprises a Hall probe for measuring a Hall voltage U _H. With the Hall probe comprising a measuring sample, the field strength H _{ges of} the magnetic field of the conductor arrangement can be determined via the Hall voltage U _H , as already described above. The magnetic field does not have to be an alternating field. The measuring sample of the Hall probe may consist of various materials with a certain charge carrier density such as metals, alloys, semiconductors, etc., wherein preferably a material with a low charge carrier density, for. As a semiconductor material such as silicon, indium antimonide, etc., is used, which causes a high Hall coefficient K _H. The larger the area A _{H of} the test sample penetrated by the magnetic field of the conductor arrangement or the thickness b of the test sample, the larger the measurable Hall voltage UN. U _H = E _H b A _H = bh

In this case, b is the width of the measurement sample in the direction perpendicular to the direction of the measurement current I _mess and perpendicular to the magnetic field, and h is the length of the measurement sample in the direction of the measurement current I _mess . An increase in the length h of the test sample only increases the resistance for the measurement current I _mess and is therefore not advantageous, but the measurement sample must have a sufficient length h to ensure that the charge carriers q to the edge of the measurement sample by the Lorenz force F _{L are} deflected to generate the electric field E _H and thus a tapped Hall voltage U _H. Consequently, it is advantageous in terms of a maximum measurable Hall voltage U _H , when the Hall probe is energized perpendicular to the magnetic field and perpendicular to the longitudinal direction y of the conductor with the measuring current I _mess and the Hall voltage perpendicular to the magnetic field and perpendicular to the Direction of the measuring current, ie in the longitudinal direction y of the conductor is tapped. In addition, the Hall voltage U _{H increases} when the measurement sample in the direction of the magnetic field has the smallest possible thickness d.

With a sensor comprising a Hall probe, a low magnetic field strength H _ges can also be measured via a readily measurable Hall voltage U _H for identifying faulty conductors in a conductor arrangement. This increases the quality of the ladder arrangements provided.

In one embodiment of the device, the sensor has a length of at least 80% [percent] of the length of the conductors. As already mentioned, the sensor can be designed to be elongated in the longitudinal direction y of the conductors, in order to increase the measurement area A _ind and thus the amplitude of the measured variable (induction voltage U _ind ). In this case, the increase in the amplitude is most effective if the sensor has as far as possible the same length and preferably at least 80% [percent] of the length of the conductors of the conductor arrangement. However, a longer or shorter sensor can also be used. By a sensor having a measuring surface of a length in the region of the conductor of a conductor arrangement, a maximum measurable amplitude of the measured variable can be achieved and thus the accuracy of the measurement can be increased. In addition, it is possible to dispense with highly sensitive and thus expensive measuring devices for the evaluation device.

The following figures show possible embodiments of the present invention and their technical environment. These figures are for convenience of understanding only and are not to be construed as limiting the scope of the present invention in any way.

1 shows schematically a conductor arrangement of a plurality of conductors.

2 schematically shows a coil for measuring an induction voltage.

3 schematically shows a Hall probe for measuring a Hall voltage.

4 to 6 schematically show sections through conductors of conductor assemblies.

7 schematically shows a measurement setup for the identification of faulty ladders.

8th schematically shows the course of a measured variable of a sensor in an exemplary measurement.

9 schematically shows the detection of a faulty conductor by means of the modulation analysis.

In 1 is schematically a conductor arrangement 10 with electrically parallel conductors 11 , which are arranged parallel to each other, shown. At the conductor arrangement 10 is a voltage U _AC 12 created. A transverse direction x 13 is perpendicular to a longitudinal direction y 14 in which the conductors extend. Such a ladder arrangement 10 can serve as a heat source for a heated disc. This can be the ladder 11 Be copper coatings, which are applied to a support structure (not shown). The contacting of the individual conductors can take place on the carrier structure as a coating or externally. The diameter of the ladder 11 is 25 μm and the distance between the conductors 11 each other is 2 mm. The conductors, once compressed in a disk between two disk elements, can be energized with 12V voltage to produce Joule heat, which, for example, can de-ice the disk.

2 schematically shows a coil 20 with one turn 21 in which an induction voltage U _ind 22 through a magnetic field 15 with the field strength H _{ges of} the conductor arrangement 10 is induced. The magnetic field 15 runs parallel to the transverse direction x 13 and a plane extending from the transverse direction x 13 and the longitudinal direction y 14 is spanned. The sink 20 is with its coil area A _ind perpendicular to the magnetic field 15 aligned to a maximum possible induction voltage U _ind 22 to induce. The induction voltage U _ind 22 would be with an increasing number N of turns 21 increase linearly.

In 3 is a Hall probe 30 in the magnetic field 15 shown schematically. The sample is made of indium antimonide. charge carrier 31 be through the magnetic field 15 which is parallel to the transverse direction x 13 runs, distracted. The deflected charge carriers 31 cause a Hall voltage U _H 32 , which at a lower and at an upper end of the measuring probe of the Hall probe 30 in the longitudinal direction y 14 is tapped. The charge carrier shown schematically here 31 is an electron that opposes the technical current direction 33 the electrical measuring current I _mess , which perpendicular to the transverse direction x 13 and longitudinal direction y 14 runs, in one direction 34 emotional. The charge carrier experiences this 31 a Lorenz force F _L 35 This one on a train 36 upwards in the longitudinal direction y 14 distracting. However, holes (not shown), which are in the technical current direction 33 move, by a Lorenz force 35 distracted, but in the opposite direction.

4 shows a section through the ladder 11 the conductor arrangement 10 in which a current I _AC 16 due to the voltage U _AC 12 flows. To each one of the ladder 11 a magnetic field is formed 17 out. The individual magnetic fields 17 overlap to a magnetic field 15 the conductor arrangement 10 , This is the field 15 substantially elliptical, wherein isometric lines of equal field strength H _ges parallel to the plane, which of the transverse direction x 13 and longitudinal direction y 14 is stretched, run. The field strength H _{ges of} the magnetic field 15 can with a sensor 40 that's a feed 41 parallel to the transverse direction x 13 subject to be measured.

In 5 is a schematic section through the ladder 11 the conductor arrangement 10 in which the current I _AC 16 due to the voltage U _AC 12 flows, being shown, being in a faulty conductor 18 no current I _AC 16 flows. The magnetic field 15 the conductor arrangement 10 therefore has a bending 19 (Dent) over the faulty conductor 18 on. Because the faulty conductor 18 not to the field 15 contributes, the isometric lines of equal field strength are H _ges above the faulty conductor 18 on the conductor arrangement 10 too bent. The sensor 40 Measures at the feed in the direction 41 a constant amplitude measure until near the faulty conductor 18 arrives. There, the amplitude of the measured variable decreases until the sensor is directly above the faulty conductor 18 is positioned where it has a minimum amplitude of the measured variable due to the most bent field there 15 measures. Thereafter, the amplitude of the measured variable increases again until the sensor is the next current-carrying conductor 11 in the direction of the feed 41 reaches where the amplitude returns to the constant value before the faulty conductor 18 reached.

6 shows schematically analogous to 5 a section through the ladder 11 the conductor arrangement 10 in which the current I _AC 16 due to the voltage U _AC 12 flows, with several faulty ladder here 18 no current I _AC 16 to lead. Therefore, the bend 19 of the magnetic field 15 even stronger, the sensor 40 right between the two faulty ladders 18 measures the lowest amplitude of the measured variable in the middle.

In 7 is a device 100 in the manner of a measurement setup for the identification of faulty conductors 18 in a ladder arrangement 10 shown schematically. The sensor 40 is executed here elongated, leaving a coil in the sensor 40 , in which an induction voltage U _{ind is} induced, has substantially the same length as the conductors 11 , This will _cause the area A _{ind of} the coil, that of the magnetic field 15 the conductor arrangement 10 is interspersed, and thus maximizes the amplitude of the measurable induction voltage U _ind . The sensor 40 will be along the feed 41 at a feed rate v _V across the conductor assembly 10 which acts as a coating on a first disk element 51 a heated disc 50 is upset, moved. A control 60 , which includes a voltage source, generates a voltage U _AC 12 connected to the conductor arrangement via terminals (not shown) 10 is created. In this case, the amplitude of the alternating voltage U ₀ 2 V is large, to burn through the head 11 to prevent. There are fluctuations in the amplitude of the induction voltage U _ind 22 that from the magnetic field 15 due to the AC voltage U _AC 12 in the coil of the sensor 40 be induced with respect to the feed 41 from an evaluation device 70 recorded and evaluated in the form of an ASIC. This can be faulty ladder 18 , which cause no or too low or too high current I _AC , are identified. A controller 80 in the form of a program of a computer then decides whether the faulty ladder 18 the heating functionality of the disk 50 too disturbing and therefore the conductor arrangement 10 needs to be repaired. Is the ladder arrangement 10 not defective or repaired, then becomes a second disc element 52 over the first disc element 51 positioned and pressed with this, so the conductor assembly 10 within the finished heated disc 50 is arranged. In the pressed state, the conductors can 11 a higher voltage (> 12 V [volts]) than in the unpressed state without burn through, since the resulting Joule heat is dissipated by the disc elements quickly.

8th schematically shows a course of a measured variable, a measurement curve 90 , a sensor 40 , Here, the measured variable is an induction voltage U _ind and plotted on the ordinate. The induction voltage is measured along a feed rate s, which is plotted on the abscissa. The induction voltage U _ind is proportional to the field strength H _{ges of} a conductor arrangement 10 that with the sensor 40 is measured to identify faulty conductors. As long as the induction voltage, ie the measured quantity in general, is between two limit values, a lower limit value U _min and an upper limit value U _max , the magnetic field is homogeneous and the conductors run over 11 the conductor arrangement 10 are error free. The fluctuations between the two limit values occur due to disturbances and noise from the environment and can be kept small by filtering methods. At a minimum 91 , which is below the lower limit value U _min , is the field strength H _{ges of} the conductor arrangement 10 so heavily distorted that one or more faulty ladder 18 must be present. The number of faulty conductors 18 results from the value of the induction voltage U _ind in the minimum 91 and from the width of the minimum 91 , Through the place 92 of the minimum may be the faulty conductor (s) 18 be accurately located in the conductor arrangement. Since it is a minimum 91 is one or more faulty conductors 18 that cause no or too little current, indicating a faulty contact or too small a diameter. At a maximum 93 , which is above the upper limit U _max , lead the identified one or more errors ladder 18 too much current (eg too thick coating or too large a diameter of the wire). Again, the localization is analogous to the minimum 91 over the place 94 of the maximum and the width as well as the value of the maximum 93 ,

9 illustrates exemplarily and schematically how faulty conductors 18 in the near range by means of a modulation of the electric field 15 . 18 can be determined, cf. traces 90 , It is illustrated by three measurements, how the measurement result with the distance 95 changed, wherein in the vicinity of a significant modulation of the field strength H _{ges of} the conductor arrangement 10 can detect. Close to the ladders 11 (For example, in a range of 0.5 to 2.0 mm [millimeters], but depending on the distance between the conductors to each other), the magnetic field 17 . 15 have a strong modulation (eg, mean magnetic flux density [TESLA]) that can be detected. The reported deviations (extremum or peak or minimum - see dashed line) from the expected modulation of an intact conductor arrangement 10 (see solid line) can be used to faulty ladder 18 close back and locate them exactly (at the location of the minimum 91 ).

In the directional statements in the preceding description, it does not matter whether the specified directions or movements take place in a mathematically positive or negative sense with respect to the other directions or movements or with respect to a global Cartesian coordinate system.

LIST OF REFERENCE NUMBERS

10

conductor arrangement

11

ladder

12

Voltage U _AC

13

Transverse direction x

14

Longitudinal direction y

15

magnetic field of the conductor arrangement

16

Current I _AC

17

magnetic field of the individual conductors

18

faulty conductor

19

Bending of the total magnetic field

20

Kitchen sink

21

convolution

22

Induction voltage U _ind

30

Hall probe

31

charge carrier

32

Hall voltage U _H

33

Measuring current I _mess

34

direction

35

Lorenz force F _L

36

train

40

sensor

41

feed

50

disc

51

first disk component

52

second pulley component

60

control

70

evaluation device

80

control

90

measured curve

91

minimum

92

Location of the minimum

93

maximum

94

Place of the maximum

95

distance

100

contraption

Claims (12)

Method for identifying faulty ladders ( 11 ) in a conductor arrangement ( 10 ) with at least two parallel conductors ( 11 ), at least comprising the steps of: a) applying a voltage, U _AC , to the conductor arrangement ( 10 ) to a magnetic field ( 15 . 17 ) to create; b) measuring a field strength, H, of the magnetic field ( 15 . 17 ) along a transverse direction x of the conductor arrangement ( 10 ); c) evaluating an amplitude of the measured field strength to detect faulty conductors ( 11 ) to identify. The method of claim 1, wherein the voltage applied in step a), U _AC , has an amplitude, U _o of less than 10V. Method according to one of the preceding claims, wherein in step b) the field strength via an induction voltage, U _{ind is} measured. Method according to claim 1 or 2, wherein in step b) the field strength is measured via a Hall voltage, U _H. Method according to one of the preceding claims, wherein in step a) as the voltage U _AC an AC voltage having a frequency f of less than 10 MHz is applied. Method according to one of the preceding claims, wherein in step b) the field strength, H over at least 80% of a length of the conductor arrangement ( 10 ) is measured in a longitudinal direction y. Method according to one of the preceding claims, wherein in step b) a measured variable is filtered. Method according to one of the preceding claims, wherein in step b) the measurement is carried out at a feed rate v _V of less than 20 cm / s along the conductor arrangement ( 10 ) he follows. Method for producing a heatable pane ( 50 ), at least comprising the steps: A) producing a conductor arrangement ( 10 ) with at least two parallel conductors ( 11 ); B) Identification of faulty ladders ( 11 ) in the conductor arrangement ( 10 ) with the method according to any one of the preceding claims; C) sorting out defective conductor arrangements ( 10 ); D) pressing the conductor arrangements ( 10 ) between a first disk component ( 51 ) and a second disk component ( 52 ). Contraption ( 100 ) set up to identify faulty ladders ( 18 ) in a conductor arrangement ( 10 ) with at least two parallel conductors ( 11 ), comprising: - a control ( 60 ) for generating an alternating voltage, U _AC , and for applying said alternating voltage, U _AC , to said conductor arrangement ( 10 ); A sensor ( 40 ) for determining a field strength, H, of a magnetic field ( 15 . 17 ), resulting from said alternating voltage, U _AC , along a transverse direction x of the conductor arrangement ( 10 ); An evaluation device ( 70 ) for evaluating an amplitude of the measured field strength, H, and for identifying faulty conductors ( 18 ). Contraption ( 100 ) according to claim 10, wherein the sensor ( 40 ) a coil ( 20 ) for measuring an induction voltage, U _ind , or a Hall probe ( 30 ) for measuring a Hall voltage, U _H. Device according to claim 10 or 11, wherein the sensor ( 40 ) a length of at least 80% of the length of the ladder ( 11 ) having.

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