Diagnostic method and measuring device for components to be inspected

Abstract

The present invention relates to a method and measuring apparatus for diagnosing a component to be inspected, comprising the following steps: operating a component to be inspected (10) at a predetermined operating point in an electrical circuit (11) for a predetermined first measurement interval (12); and detecting a measurement signal and an excitation signal (13) in the circuit in a time-dependent manner during this first measurement interval, wherein the excitation signal is a signal from a passive component (14) in the circuit that is in a predetermined first excited state (15) at the start of the first measurement interval, and the measurement signal is generated from the superposition of the excitation signal of the passive component and the operating signal of the component to be inspected.

Description

Technical Field

[0001] The present invention relates to the diagnosis of electrochemical elements, such as galvanic primary or secondary cells, batteries, electrolytic cells or fuel cells or fuel cell stacks.

[0002] In order to more deeply analyze the state of an electrochemical element (for example, in a Li-ion battery, and also in fuel cells and electrolytic cells), impedance spectroscopy is known in particular.

[0003] In this method, the cell (such as a Li cell or a fuel cell) is periodically excited externally during operation. Such excitation may be a periodic increase and decrease in the output current (for example, via a frequency-modulated load), or an excitation voltage superimposed on the operating voltage. Generally for this purpose, a frequency generator that generates a completely symmetric signal (such as a sine wave) is used, and this signal is transmitted to the cell by a voltage source (referred to as a "potentiostatic") or an electrical load (referred to as a "galvanostatic"). The generated response signal (voltage fluctuations in the case of galvanostatic excitation, or current signal fluctuations in the case of potentiostatic excitation) is measured in the cell to be inspected. By Fourier analyzing the phase shift generated from the excitation signal to the response signal at different excitation frequencies, information about the real and imaginary parts of the cell-specific impedance can be obtained. The underlying functions or processes can be found, for example, in many books and publications.

[0004] This method is technically time-consuming and prone to interference for a number of reasons. That is, the generation of a periodic excitation signal usually requires a frequency generator that can generate a wide spectrum of various frequencies. Generally, in order to be able to image the complex impedance image depending on the frequency, many frequencies are passed for each measurement.

[0005] Furthermore, these signals must be transmitted to the cells cleanly and faithfully using appropriate voltage sources / current sinks, etc. Interfering effects from cables and lines or the measurement structure regarding inductance and capacitance must be avoided by considerable effort, or measured using calibration, so that a "clean" diagnosis of the measurement cell being tested can be derived from this analysis. Ideally, the structure must be identical for all (repeated) measurements (e.g., temporal aging measurements, or after damage to the measurement cell, and possibly temperature effects, etc.), i.e., it must be reproducible positionally and / or structurally. Similarly, external disturbances in the signal path of the object being tested / excited should be avoided (e.g., abrupt changes in load during the measurement cycle). The signal being tested must be elucidated with extreme precision (both signal intensity and temporal correlation for excitation). The procedure requires specific measurement times (especially for broad frequency spectra (depending on the observed characteristics of the cell being tested)). This procedure is difficult to perform (especially in mobile applications and driving operations (e.g., online analysis in vehicles)). The limitations described above regarding the required hardware significantly restrict its use in mobile applications or applications that may operate without being stationary for extended periods. Furthermore, the necessary equipment and structural modifications are relatively expensive.

[0006] Therefore, the fundamental problem of the present invention is to provide a method and apparatus for cell diagnosis that avoids the difficulties described above.

[0007] This problem is solved by the method and apparatus described in the independent claim. Advantageous developments are shown in the dependent claims.

[0008] The diagnostic method according to the present invention is suitable, for example, for impedance analysis of batteries, fuel cells, or electrolytic cells or other electrochemical elements. These are referred to as components under inspection within the framework of the present invention. In particular, the method and apparatus according to the present invention can be advantageously used for diagnosing fuel cells (stacks) in vehicles.

[0009] To carry out the method according to the present invention, the component under inspection is operated at a predetermined operating point in the circuit during a predetermined first measurement interval. The predetermined operating point here specifically means a defined, reproducible, and / or preferably constant operating point, thereby advantageously enabling the reproducibility and comparability of the diagnostic method according to the present invention.

[0010] During the first measurement interval, the passive component is connected to the circuit. At the start of the first measurement interval, the passive component is in a preset first excited state. During the duration of the measurement interval, according to the present invention, the circuit detects the measurement signal and excitation signal of the passive component in a time-dependent manner. The measurement signal is generated from the superposition of the excitation signal of the passive component and the operation signal of the component under inspection.

[0011] Subsequently, preferably, the measurement signal and excitation signal can be evaluated, from which an estimate of the state of the component being inspected can be derived.

[0012] For example, this passive component may be a capacitor, a coil (inductance), or a resistor. In this case, the pre-set excitation state may correspond to, for example, charging by a specific voltage in the case of a capacitor, a specific temperature for a resistor (which is temperature-dependent), or a specific magnetization state for a coil. However, the pre-set excitation state may also be the fundamental state, that is, for example, a voltage of 0 in the case of a capacitor, or a state of no magnetization in the case of a coil.

[0013] While the passive component is connected to the circuit, during the first measurement interval, this passive component outputs an excitation signal to the circuit.

[0014] The excitation signal for a capacitor is, for example, the charging current or the discharging current. This (discharging) charging current follows a characteristic time course depending on the capacitor's design. Different capacitors may differ, for example, in their capacitance and voltage rating, as well as their charging and discharging characteristics and their time constants (τ). Typical capacitances are, for example, in the range of 200pF to 2mF.

[0015] Correspondingly, the resistance may differ in its temperature dependence, and the inductance may differ in, for example, its permeability, number of turns, etc. These properties of passive components are crucial not only to the excited state but also to the course of the excitation signal in the circuit, and within the framework of this application, they are referred to as the characteristics of each passive component.

[0016] The preset measurement interval is the time interval at which measurements are taken. Preferably, the preset measurement interval can be selected depending on the characteristics of each passive component. For capacitors, a favorable measurement interval is, for example, 3 to 4 times the capacitor time constant. The duration of the measurement interval is, for example, 0.5 ms to 5 s. A duration between 100 ms and 1 s, for example, 150 ms, is favorable.

[0017] According to one preferred evolution of the method according to the present invention, after the first measurement interval has ended, at least one additional passive component is connected for another predetermined measurement interval. This is done in a predetermined second excited state at the start of the other measurement interval. During the duration of the other measurement interval, the circuit detects the measurement signal and the excitation signal again in a time-dependent manner. In this case, the excitation signal is generated by at least one additional passive component, and the measurement signal is obtained from the superposition of the excitation signal and the operating signal of the component under test. Preferably, the first passive component is disconnected from the circuit by, for example, opening a switch before the other measurement interval. The first passive component can then be advantageously returned to a predetermined first excited state. In the case of a capacitor, this can be done, for example, by connecting it to a voltage source and charging the capacitor accordingly.

[0018] A particular advantage of the described modification is that the first passive component and at least one other passive component have different characteristics and / or each takes on at least different pre-set excitation states. This allows for the sequential generation of different excitation signals in the circuit, which then overlap with the operating signals of the component under inspection, thereby generating different measurement signals. This allows for obtaining additional information about the state of the component under inspection.

[0019] Here, it is also possible to sequentially connect multiple other passive components to the circuit for each pre-set measurement interval. Particularly advantageous is the sequential connection of three, four, or five different passive components, each with different characteristics (reference parameters, time constants, etc.), to the circuit and detection of their respective measurement signals. In this case, both combinations of the same type of passive components, i.e., two or more capacitors with different characteristics, and combinations of different types of passive components, i.e., combinations of capacitors, coils, and / or resistors, are possible.

[0020] In one modified embodiment of the method according to the present invention, which has multiple different passive components, it is also possible to sequentially combine measurement intervals of different lengths. Preferably, the length of the measurement interval is suited to the characteristics of each passive component. That is, when different passive components are connected alternately or sequentially, measurement intervals of different lengths may follow in sequence.

[0021] According to one alternative modification of the method of the present invention, it is also possible to sequentially transition the same passive component to different excited states and perform multiple measurements sequentially starting from different excited states. Thus, after the first measurement interval (and / or another) has ended, the first passive component is transitioned to another preset excited state different from the first excited state, and the measurement of the excitation signal and measurement signal is repeated in another measurement interval, so that the first passive component is in a different excited state different from the first excited state at the start of the other measurement interval. Advantageously, this modification allows for the generation of different excitation signals and measurement signals and avoids the additional cost of other passive components.

[0022] Naturally, the modified forms described can be combined with each other. Additionally, various passive components, each capable of taking on different excited states, can be combined.

[0023] According to the method of the present invention, a time-dependent excitation signal can be generated in a circuit using one or more passive components and superimposed on the operating signal of the component under inspection. In this case, by evaluating the temporal correlation between the excitation signal and the measurement signal, the impedance characteristics of the component under inspection can be advantageously estimated.

[0024] The measurements described above can be repeated, which is particularly advantageous. For this purpose, after each predetermined measurement interval has ended, the respective predetermined excited states for the passive components can be recreated, and then a new measurement can be performed. In the case of a capacitor, this can be done, for example, by charging with a predetermined voltage, and for a resistor, by heating to a predetermined temperature.

[0025] A particularly advantageous development of this method involves performing measurements periodically at a specific repetition frequency. In the simplest case, this is achieved by periodically switching the first passive component to its excited state, connecting it to a circuit to generate an excitation signal for the duration of the measurement interval, switching it to the excited state again after the measurement interval, and then the first passive component can again send an excitation signal to the circuit, and so on. A typical repetition frequency may be in the range of 1 Hz to 10 kHz, and preferably in the range of approximately 1 kHz to 3 kHz.

[0026] Therefore, by performing the measurement periodically, a periodic excitation signal is generated in the circuit. Preferably in this case, the time-dependent measurement of the excitation signal and the measurement signal is not limited to individual measurement intervals (in which time the passive components are connected to the circuit), but is performed continuously over at least multiple periods. Therefore, the measured excitation signal and measurement signal obtained in this way are also periodic at the repetition frequency. In this case, the excitation signal of the capacitor corresponds, for example, to a periodic current pulse having a characteristic course for each capacitor.

[0027] The period is advantageous not only when it consists of a single excitation pulse, that is, a single excitation signal from a single passive component, but also when multiple different excitation pulses are combined. As already explained above, this can be achieved by having the passive components sequentially generate different excitation pulses starting from different excited states, or by having two or more different passive components each sequentially emit excitation signals. Basically, all the combinations of excitation signals and measurement intervals described above are possible. In this case, an excitation pattern is obtained by a sequence of multiple excitation pulses or excitation signals from one or more passive components and the corresponding measurement interval, and this excitation pattern is then preferably repeated periodically.

[0028] By performing it periodically as described for the method according to the invention, it is possible, in particular advantageously, to evaluate periodic excitation signals and periodic measurement signals with respect to the frequency-dependent impedance characteristics of the component to be inspected by means of Fourier analysis or another mathematical evaluation.

[0029] According to another aspect, the invention includes a measuring device for diagnosing a component to be inspected, which has a component to be inspected that can operate at a preset operating point in a circuit during a preset measurement interval. This circuit further has at least one passive component that can transition to a preset excitation state at the start of the measurement interval in order to send an excitation signal to the circuit during the measurement interval. This measuring device further includes at least one measuring instrument for measuring a measurement signal that depends on time and / or for measuring an excitation signal that depends on time. The measurement signal results from the superposition of the excitation signal of the passive component and the operating signal of the component to be inspected. In particular, separate measuring instruments for measuring the measurement signal and for detecting the excitation signal may be provided respectively. However, it is also possible to perform two measurements in one device.

[0030] The measurement signal and the excitation signal are generally the current course and voltage course in the circuit. Therefore, at least one measuring instrument is preferably configured to detect the voltage and / or current flow applied to the component to be inspected in the circuit depending on time. Preferably, a current measuring instrument and a voltage measuring instrument are included in the circuit. The measurement of current and voltage can also be performed in one common device.

[0031] According to one preferred embodiment of the measuring device according to the present invention, the passive component is a capacitor whose preset excitation state is charging by a preset voltage. The capacitor can preferably be connected to the circuit by closing the first switch and can be connected to a current source and / or a voltage source by closing the second switch. Thus, when the second switch is closed, it is charged by the preset voltage, and when the second switch is open and the first switch is closed, a discharge signal is sent as an excitation signal. The passive component is, for example, connected in parallel to the component to be inspected.

[0032] It is also possible to use one or more capacitors as a voltage source or a current sink. Here, the charging curve or the discharging curve of the capacitor used when connecting or disconnecting from the circuit maintaining the operation of the cell to be inspected is used as an excitation signal.

[0033] The passive component may be a coil (inductance) or an electrical resistor. In the case of inductance, the preset excitation state is, for example, a magnetization state. By applying an external magnetic field or using a second coil outside the circuit, the characteristics of the inductance can be changed, thereby enabling the changed excitation state to be taken and / or the changed excitation signal to be sent to the circuit.

[0034] For this purpose, an additional device for selectively changing the characteristics of the passive component or the characteristics of its respective excitation state (e.g., magnetization / charge state) can be provided in the measuring device. This device includes, for example, a temperature control device for adjusting the temperature of a coil, an electromagnet, or a passive component (e.g., a resistor).

[0035] In addition to at least one passive component, the measuring device according to the present invention may have at least one other passive component, which can be connected to the circuit either alternatively to or in exchange for the first passive component, and preferably has different characteristics from the first passive component. In particular, there may be three, four, five or more passive components, which are connected to the circuit sequentially.

[0036] It is also possible to provide two passive components of the same structure, each capable of being connected to the circuit alternately and transitioning back to an excited state. This allows for the generation of excitation pulses at shorter time intervals, thereby accelerating measurements.

[0037] Furthermore, the measuring device preferably includes an evaluation device, which allows for the evaluation of the impedance characteristics of the measured time-dependent excitation signal and the measured signal using, for example, Fourier analysis, particularly by the Fast Fourier Transform.

[0038] The method and measuring apparatus according to the present invention can generate an excitation signal that is applied periodically and repeatedly to a component under inspection, even if it is not perfectly symmetrical. Periodic excitation can be generated by periodically connecting or disconnecting at least one passive component to the circuit under inspection.

[0039] In another embodiment, the present invention includes a control device for carrying out a method according to the present invention, the control device being configured to drive and control a measuring device according to the present invention to carry out a method according to the present invention.

[0040] The control device preferably includes communication means suitable for carrying out the method according to the present invention, thereby transmitting corresponding control signals or switch signals to each component of the measuring device, particularly switches, current sources or voltage sources, and at least one measuring instrument. The switches and current / voltage sources and at least one measuring instrument are preferably configured to be controllable for this purpose, particularly electronically, via the corresponding communication means. However, the at least one measuring instrument may be incorporated into the control device.

[0041] The present invention further includes, according to one other aspect, an evaluation device configured to evaluate the temporal correlation between an excitation signal and a measurement signal obtained by a method and / or a measuring device according to the present invention. The evaluation device preferably includes a computing unit equipped with a processor and is configured to receive time-dependent measurement and excitation signals via appropriate communication means. For example, a first measuring instrument and a second measuring instrument may also be incorporated into the evaluation unit. The evaluation device is thus preferably configured to evaluate the measurement and excitation signals with respect to the impedance characteristics of a component under test.

[0042] The evaluation device and the control device described may be combined into a single device or they may be separate devices. Preferably, the evaluation device and control device are provided as components in a vehicle. The evaluation device and control device may be incorporated, for example, into the fuel cell control unit of a vehicle. In this case, it is advantageous that the corresponding measurements and analyses of the fuel cell can be performed in the vehicle. This may be done, for example, on a time-planned basis (e.g., at regular intervals) or when a particular operating state changes (e.g., during a shutdown process).

[0043] The present invention will be described in more detail below with reference to the drawings. [Brief explanation of the drawing]

[0044] [Figure 1]This is a schematic diagram showing a first embodiment of the measuring device according to the present invention. [Figure 2] This is a schematic diagram showing a flowchart illustrating the process of the method according to the present invention, based on a first modified embodiment. [Figure 3] This is a schematic diagram showing an exemplary excitation signal according to another preferred modified embodiment of the method according to the present invention. [Figure 4] This is a schematic diagram showing a second embodiment of the measuring device according to the present invention.

[0045] In the first embodiment of the measuring device according to the present invention shown in Figure 1, the component 10 to be inspected is connected to a load 16 in the circuit 11. A first measuring instrument 46 is used to measure the voltage applied to the component 10 to be inspected. A second measuring instrument 47 is provided to measure the current flowing through the circuit. A first passive component 14 can be connected to the circuit in parallel with the component 10 to be inspected using a first switch 40. The first passive component 14 (e.g., a capacitor) can be connected to another voltage source 45 via a second switch 44, thereby charging the first passive component 14 with the voltage and thereby transitioning it to a preset excited state.

[0046] Figure 2 illustrates the process of the method according to the present invention in a preferred modified embodiment. In the first step 1, a fuel cell or fuel cell stack is connected to a load at a certain load point as the component to be inspected (e.g., a battery, vehicle drive unit, or electrical load). In the second step 2, for excitation, a capacitor with appropriate parameters (appropriate capacitance and voltage withstand voltage, charging characteristics, and discharging characteristics) is brought to its preset excited state as a passive component, i.e., pre-charged with a fixed reference voltage (e.g., via a 12V onboard power grid in a vehicle, or a 5V voltage condition of a controller). In step 3, for modulation of the fuel cell current, the capacitor is connected in parallel (generally, for example, at 200V) to the circuit consisting of the fuel cell and the load for a preset measurement interval. The charging current (resulting from the capacitor's characteristics and the voltage difference relative to the fuel cell voltage) is superimposed on (in this case increases) the current load current of the cell. After the measurement interval (whose duration corresponds, for example, to 3 to 4 times the capacitor's time constant τ) has elapsed, the capacitor is disconnected from the circuit (for example, by a relay or transistor). Optionally, in another step 4, the charge can then be discharged through a load at a lower voltage level or to the voltage source of step 2. Preferably, the contained energy can be used to operate related consuming devices (e.g., controller, 12V battery charger, lighting module, etc.). This minimizes the energy wasted from the cell being tested, thereby increasing the absolute efficiency of the system / vehicle.

[0047] This method is selectively repeatable. For this purpose, the capacitor is returned to its original excited state (pre-conditioned) in step 2. In step 3, the capacitor can be connected to the circuit again for the duration of one measurement interval. In a preferred modification, multiple capacitors can be connected alternately for excitation. This reduces the measurement time (or the waiting time until the component under test is re-excited) and increases the efficiency of the analysis.

[0048] Particularly preferable, multiple different capacitors (with different characteristics / time constants) can be connected sequentially or periodically in alternation. This creates different excitation modes, which can be used as analogies to different excitation frequencies in classical methods.

[0049] Figure 3 illustrates the excitation signals generated by three capacitors connected sequentially. During the first measurement interval 12, a first capacitor having a preset excitation state 15 is connected. The resulting excitation signal 13 has specific characteristics due to a first time constant. In the subsequent second measurement interval 22, a second capacitor 24 (shown in Figure 4) having an excitation state 25 is connected in place of the first capacitor 14.

[0050] Subsequently, instead of the second capacitor, a third capacitor 34 (shown in Figure 4) having a third excited state 35 is connected for the duration of the third measurement interval 32. The three capacitors (14, 24, 34) may have different excited states (not shown here) or, for example, different time constants τ. As a result, the characteristics of the excitation signal 13 differ among the three excitation pulses shown. In this way, different transitions occur in the analysis of the measurement signal (in this example, the operating voltage of the fuel cell is measured over the excitation time). In the illustrated embodiment, the durations of the first measurement interval (12), the second measurement interval (22), and the third measurement interval (32) together correspond to a period duration 48. Thereafter, the first capacitor 14 and measurement interval 12 can be repeated. Subsequently, the periodic measurement and excitation signals thus generated can be analyzed using Fourier analysis or another appropriate mathematical evaluation to determine the phase transition (and thus the impedance characteristics). Characteristic signal responses are obtained depending on the operating and functional states of the components being inspected. These signal responses allow for interpretation of the aging state, "health state," or current operating state.

[0051] One embodiment of a measuring device according to the present invention, comprising three passive components, is illustrated in Figure 4. The measuring device in Figure 4 differs from the device shown in Figure 1 in that it is provided with three different passive components 14, 24, and 34, which can be connected in parallel to the component under inspection either selectively, sequentially, or simultaneously in parallel, via their respective switches 41, 42, and 43. The same components are denoted by the same reference numerals as in Figure 1. Passive components 24, which can be connected via switch 42, and passive components 34, which can be connected via switch 43, are provided in parallel with passive component 14, which can be connected to the circuit via switch 41.

[0052] Switch 40 allows all three passive components 14, 24, and 34 to be disconnected from the circuit. Through switch 44, the passive components 14, 24, and 34 can be connected to a voltage source 45 or a current source 45. The three passive components 14, 24, and 34 may be of the same type, having identical or different characteristics. However, they may also be of different types. Preferably, the three passive components 14, 24, and 34 are connected to the circuit 10 alternately to emit excitation signals during the duration of measurement intervals 12, 22, and 32, respectively. However, it may also be effective to connect two or more passive components to the circuit 10 simultaneously to emit a common excitation signal. Switches 41, 42, and 43 allow any combination of the three passive components to be connected to the circuit. This allows for the advantageous generation of different excitation signals with a small number of passive components, enabling more accurate analysis of the component under test. The evaluation device 50 can evaluate the measured measurement signal and excitation signal. [Explanation of Symbols]

[0053] 10 Components to be inspected 11 Electrical Circuits 12. First measurement interval 13 Excitation signal 14. First passive component 15 Pre-set first excited state 16 load 22 Another (second) measurement interval 24 Second passive component 25 Another pre-set excitation state 32 Another (third) measurement interval 34 Third passive component 35 A pre-set third excited state 40 Switch1 41 Switch First passive component 42 Switch Second passive component 43 Switch Third passive component 44 Switch 2 45 Current Source / Voltage Source 46. ​​First measuring instrument 47. Second measuring instrument 48 cycles 50 Control devices / evaluation devices

Claims

1. A method for diagnosing a component (10) to be inspected, the following steps: a) In the electrical circuit (11), the step of operating the component (10) to be inspected at a predetermined operating point for a predetermined first measurement interval (12), b) During the first measurement interval (12), the circuit (11) detects a measurement signal and an excitation signal (13) in a time-dependent manner, The excitation signal (13) is a signal from a passive component (14) in the circuit that is in a preset first excited state (15) at the start of the first measurement interval (12), and the measurement signal is a method for diagnosing a component (10) to be inspected, which is generated from the superposition of the excitation signal (13) of the passive component (14) and the operation signal of the component (10) to be inspected.

2. Another step, namely, c) After the first measurement interval (12) has ended, a step of connecting at least one other passive component (24, 34) for a predetermined additional measurement interval (22, 32), wherein the at least one other passive component (24, 34) is in a predetermined additional excited state (25, 35) at the start of the additional measurement interval (22, 32), d) A method for diagnosing a component (10) to be inspected according to claim 1, comprising the step of detecting the measurement signal and the excitation signal in the circuit in a time-dependent manner over the other measurement intervals (22, 32).

3. A method for diagnosing a component member (10) to be inspected according to claim 2, wherein the passive component (14) and the at least one other passive component (24, 34) have different characteristics and / or each has a different preset excitation state (15, 25, 35).

4. Another step, namely, e) After the first measurement interval (12) and / or the second measurement interval (22) has ended, the passive component (14) is moved to a predetermined excited state (25, 35) different from the first excited state (15), and the steps a) and b) are repeated. A method for diagnosing a component (10) to be inspected according to any one of claims 1 to 3, wherein at the start of the other measurement interval (22, 32), the first passive component (14) is in a different excited state (25, 35) than the first excited state (15).

5. Another step, namely, f) A method for diagnosing a component (10) to be inspected according to any one of claims 1 to 4, comprising the step of evaluating the measurement signal in order to determine the impedance characteristics of the component (10) to be inspected by evaluating the temporal correlation between the excitation signal (13) and the measurement signal.

6. A method for diagnosing a component (10) to be inspected according to any one of claims 1 to 5, comprising periodically repeating step a) and step b), and optionally additionally step c), and step d) and / or step (e).

7. A method for diagnosing a component (10) to be inspected according to claim 6, comprising evaluating the time-dependent measurement signal for frequency-dependent impedance characteristics by Fourier analysis or other mathematical evaluation.

8. A measuring device for diagnosing a component to be inspected, comprising a component to be inspected (10) in a circuit (11) that is operable at a predetermined operating point during a predetermined measurement interval (12, 22), The circuit (11) further, - During the measurement interval (12, 22), in order to send an excitation signal (13) to the circuit (11), at the start of the measurement interval (12, 22), at least one passive component (14, 24) capable of transitioning to a preset excitation state (15, 25) is provided, - A measuring device for diagnosing a component (10) under inspection, comprising: at least one measuring instrument (46, 47) for measuring a measurement signal in a time-dependent manner during the measurement interval (12, 22) and / or for measuring the excitation signal (13), wherein the measurement signal is generated from the superposition of the excitation signal (13) of the passive component (14, 24) and the operating signal of the component (10) under inspection.

9. A measuring device for diagnosing a component (10) under inspection according to claim 8, wherein at least one of the measuring instruments (46, 47) is configured to capture the voltage and / or current flow applied to the component (10) under inspection in the circuit (11) in a time-dependent manner.

10. The measuring device for diagnosing a component (10) to be inspected according to claim 8 or 9, wherein the passive component (14, 24) is a capacitor whose preset excited state (15, 25) is a capacitor charged by a preset voltage.

11. The capacitor (14) is connectable to the circuit (11) by closing a first switch (40), and connectable to a current source and / or voltage source (46) by closing a second switch (44), thereby being charged by voltage when the second switch (44) is closed, and sending an excitation signal (13) when the second switch (44) is open and the first switch (40) is closed, the measuring device for diagnosing a component (10) to be inspected according to claim 10.

12. A measuring device for diagnosing a component (10) to be inspected according to any one of claims 8 to 11, wherein at least one of the passive components (14, 24) is connected in parallel to the component (10) to be inspected.

13. The measuring device for diagnosing a component (10) to be inspected according to claim 8 or 9, wherein the passive component (14) is a coil whose preset excitation state is a preset magnetization state.

14. A measuring device for diagnosing a component (10) to be inspected according to claim 13, wherein the coil is capable of transitioning to a changed excited state by applying an external magnetic field.

15. The measuring device for diagnosing a component (10) to be inspected according to any one of claims 8 to 14, wherein the measuring device has at least one other passive component (24, 34) that can be connected to the circuit (11) in an alternative manner to the first passive component (14) and has different characteristics from the first passive component (14).

16. A control device (50) configured to drive and control the measuring device according to any one of claims 8 to 15, and to carry out the method according to any one of claims 1 to 7.

17. An evaluation device (50) configured to evaluate a measurement signal obtained by the method described in any one of claims 1 to 7 and / or by the measuring device described in any one of claims 8 to 15, in order to determine the impedance characteristics of the component member (10) to be inspected.

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