EP2252983A1

EP2252983A1 - Anti-theft surveillance system and method for surveilling an electrical device, especially a solar module

Info

Publication number: EP2252983A1
Application number: EP08846619A
Authority: EP
Inventors: Erhard Dumps
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-11-05
Filing date: 2008-10-16
Publication date: 2010-11-24
Also published as: WO2009059877A1; DE102007052653A1; DE102007052653B4; CA2704605A1; US20100295680A1

Abstract

An anti-theft surveillance system, especially for one or more solar modules, comprises an input for supplying a time-varying control signal, two connecting terminals between which the article to be surveilled is connected, and a switch, controlled by the control signal, for supplying a surveillance signal to one of the connecting terminals. A comparator circuit is coupled to the input and to the other of the two connecting terminals and is used to detect a change in a time profile between the control and the surveillance signal.

Description

description

Theft monitoring device and method for monitoring an electrical device, in particular a solar module

The invention relates to a theft monitoring device for devices, in particular for one or more solar modules. The invention further relates to a method for monitoring an electrical device, in particular one or more solar modules.

Theft monitoring devices are becoming increasingly important, especially in devices whose local situation makes permanent personal monitoring more difficult. This applies, for example, electrical consumers, such as neon signs, bulbs, but also energy producers in the field of renewable energy, such as Fotovol- taiksysteme. Especially the latter are often appropriate in areas with a rather low population density.

While photovoltaic systems for generating electricity by solar energy by their ways of functioning during the daytime already subject to some theft protection, they are exposed to increased risk during the night. In addition, photovoltaic systems are particularly easy to replace due to their structure. Conversely, the relatively simple mechanical construction leads to an increased risk of theft during the night in which the photovoltaic systems do not produce electricity and thus theft is not recognized directly by the inrush or voltage. The same applies to electrical loads such as bulbs while in their off state.

Since theft of such consumers or of photovoltaic systems, in particular in the case of large solar parks, entails high replacement costs, there is of course the need to provide theft monitoring devices which are particularly suitable for such devices. It is also appropriate to specify a procedure for monitoring consumers or producers.

The subject matters of the present independent claims take into account the above needs.

They are based on the principle that electrical devices conduct electricity even when switched off. This stream can be used to detect a theft or tampering attempt and to trigger a corresponding alarm signal. The term electrical device is understood to mean any device that is capable of producing or consuming electrical energy. These include, but are not limited to, generators, photovoltaic systems such as solar cells or modules, wind turbines, electrical consumers, lighting, neon signs, fluorescent or spotlights, transformers, and more. However, the term also includes devices that operate without power, but additionally have a circuit that is monitored and whose properties change during a manipulation attempt.

The invention proposes to apply an accidental signal to an electrical appliance, for example one or more solar modules, and to detect a change in the time course of this signal. A change over time called by a theft or manipulation attempt due to a mechanical removal of the electrical device can be detected by a comparison with a corresponding control signal and an alarm signal generated.

The theft monitoring device is particularly suitable for this because it uses the consumer and its electrical properties directly. Thus, the theft monitoring device preferably always be active when the electrical device to which the theft monitoring device is connected, is itself disabled. For example, in the case of solar modules during the nighttime, in which the solar modules themselves do not consume electrical power. In the case of electric bulbs, more generally in the case of an electrical load, or more generally in an electrical device, the theft monitor may be active when the electrical load or the device itself is turned off and thus fails to perform its operational function.

Nevertheless, the theft monitoring device according to the invention is not limited thereto. Basically, the stealing device can be used for any device that has a circuit that can be monitored.

The theft monitoring device is thus particularly suitable for protecting the device to be monitored against theft, damage or similar manipulation during its inactive time.

In one embodiment, the theft monitoring device comprises an input for supplying a time-varying control signal. Furthermore, at least two provided terminal clamps which are suitable to be coupled with an electrical device to be monitored against theft, damage or the like. This can be an electrical consumer but also an energy generator. The theft monitoring device further comprises a switch controlled by the control signal for supplying a monitoring signal at one of the connection terminals. A comparison circuit is coupled to the input for supplying the control signal and to the other of the connection terminals and configured to detect a change in a time profile between the control signal and the monitoring signal.

It is expedient if the control signal has a temporally randomly changing amplitude or a temporally randomly changing logical level. The randomness makes it difficult to manipulate the control signal from which the monitoring signal is generated. For example, the control signal may have a random rectangular shape.

In one embodiment, the theft monitoring device comprises a current source controllable via the switch, which is designed to deliver a current to the one terminal in response to the control signal. Thus, a time varying current flows through the electrical device connected between the terminals. The time profile of the current signal is detected by the comparison circuit, compared with the control signal and determines therefrom a pointing to a theft, damage or the like change. The comparison circuit can be connected on the output side with a signal generator, for example a radio transmitter, a lighting means or even a loudspeaker. Also suitable is a camera that takes a picture of the manipulator. In a corresponding theft or manipulation or damage attempt, the comparison circuit thus responds, generates a corresponding signal, which initiates suitable measures.

This includes optical and / or acoustic signals, as well as radio signals that are sent to authorities such as police or other security services. Cameras for capturing surveillance images can also be initialized.

In some cases, a propagation delay occurs in the monitoring signal due to the electrical device located between the terminals. In order to correct and compensate for this delay, in one embodiment of the invention a delay circuit is provided which compensates for the propagation delay caused by the device to be monitored in the monitoring signal.

In one embodiment, this delay circuit is arranged between the input and supply of the control signal and the comparison circuit. For example, the delay circuit may comprise one or more delay elements, which delay the control signal by the time period corresponding to the propagation delay of the monitoring signal by the consumer.

In another embodiment, the delay circuit may comprise a filter which is connected to the output of the comparison circuit. In order to prevent manipulation, in a development of the invention, the theft monitoring device additionally comprises a voltage detector which is coupled on the input side to one of the connection terminals. This is designed to compare a voltage applied to the terminal voltage to a reference value. The voltage detector prevents bridging of the terminals, as this leads to a momentary change in the voltage. The voltage detector can be designed as a window discriminator with an adjustable reference threshold.

In another embodiment, a current detection device may be provided in front of the one of the terminals, which in a change of the flowing through the terminal

Electricity appeals. The additional measures tamper with manipulation attempts, for example, by shorting the two terminals or replacing the device with another element.

The theft monitoring device is preferably housed in a secure housing. This housing may additionally be connected to a detector which detects an unauthorized opening of the housing and triggers a corresponding alarm. As a result, the theft monitoring device is additionally protected against spying or a tampering attempt.

In the following, the invention is explained in more detail by means of several exemplary embodiments with reference to the drawings. The disclosed principles and embodiments are not limited to the illustrated embodiments and in particular to the device to be monitored shown there. Rather, the anti-theft device according to the invention and the method are suitable for protecting any device from theft which has a circuit. Elements with the same or similar functionality bear the same reference numerals.

To show

1 shows a section of a solar park with a theft monitoring device according to the invention,

FIG. 2 is a block diagram of a theft monitoring device for explaining various aspects of the invention;

FIG. 3 is a block diagram of a possible embodiment;

FIG. 4 shows a signal-time diagram for illustrating the time profile of various signals of the theft-monitoring device.

Figure 1 shows a section of a solar park, in which a plurality of solar modules are connected in series and in parallel with each other to generate electricity in daylight. The individual solar modules are arranged in strands, of which two, namely the strands 20a and 20b, are shown here by way of example. Each of the strings may comprise a number of individual solar modules connected in series, each module in turn comprising a plurality of series connected solar cells. Such a solar cell essentially contains a pn junction, which is operated for power generation in the reverse direction. Incident light generates within the depleted space charge zone an electron hole pair, which is spatially separated due to the internal voltage and thereby leads to a current flow.

The series-connected solar modules are combined in a strand 20a and 20b, and connected to power lines Sl and S2. Several such strands are connected in parallel to an inverter 10 via the power lines Sl and S2. The inverter 10 generates an alternating current from the direct current output by the solar modules and feeds it into the supply network.

For theft prevention or monitoring of the individual strands and thus also of the individual solar modules, corresponding monitoring devices 30a and 30b are arranged between the main lines S1 and S2 and the respective solar strands 20a and 20b. These are additionally equipped with their own independent power supply. In the present embodiment, the inverter 10 provides a corresponding power supply via the power supply line SV. Alternatively, a battery or a battery may be provided. The latter can for example be charged by the solar modules particularly easily during the day. Possibly. For a rechargeable battery, additional elements are necessary to transform the voltage of the rechargeable battery to the required monitoring voltage.

During the day in which the individual solar modules of the strings 20a and 20b provide power, the monitoring be bridged means 30a and 30b, so that the solar modules of the strands 20a and 20b are coupled to the main power lines Sl and S2. During the nighttime, when the solar modules of the strands do not generate any energy, the monitoring devices are active and monitor possible damage or theft attempts of individual solar modules within the strands.

A monitoring device 30b is shown enlarged by way of example here. The monitoring device is housed in a housing 300, which is closed and is checked by one or more sensors 52 for damage. As a result, for example, an unauthorized opening of the housing 300 of the monitoring device, but also a removal or damage to the monitoring device can be avoided. The detector 52 may be formed, for example, as a vibration detector. Attempts to recite or otherwise open the housing are thus detected and delivered to a housing monitoring device 50. In an attempt to damage the case thus or to open without authorization, the housing monitoring device 50 generates a corresponding alarm signal on the alarm line AL.

In addition to a vibration sensor, other sensors can be used beyond that register a change in the characteristics of the monitoring device and in particular of the housing and trigger a corresponding alarm. Thus, in addition, the voltage or the current on the power supply line or the alarm line can be monitored. In addition, a circuit board 310 with the theft monitoring device 400 is accommodated in the housing 300. In addition to the actual theft monitoring device 40, the circuit board 310 also includes additional switches 42, which are currently controlled by the theft monitoring device 40. The theft monitoring device 40 also has a supply line to the power supply SV and to the alarm line AL.

The switches 42 are designed such that they place the supply lines S1 'and S2' of the solar modules either on the supply line of the theft monitoring device 40 or on the external power lines S1 and S2. For example, the theft monitoring device 40 switches the solar modules to the power lines S1 and S2 during the day. During the night, the solar modules of the respective solar string connected to the lines S1 'and S2' are connected to the theft monitoring device 40.

Alternatively, the switches 42 can also be controlled by the inverter 10. This controls the theft monitoring device and activates or deactivates it if necessary. In such a case, the theft monitoring device 40 on the housing 300 additionally contains an interface, which is connected to the inverter. Control signals for the theft monitor 40 and switches 42 are sent via the interface. The control signals may be encrypted to prevent tampering. Likewise, a clear identification, for example by an authentication method can be provided. In its operation, the theft monitoring device 40 monitors the individual solar modules connected to the lines S1 'and S2' in such a way that an alarm signal is triggered when such a module is removed. This is achieved by sending a corresponding monitoring signal from the monitoring device 40 through the solar modules. By comparing a temporal course of the monitoring signal delivered to the solar modules with a corresponding control signal, a change caused by a damage or theft attempt can be detected. A corresponding detection leads to a signal on the alarm line AL.

The alarm line AL may, for example, be equipped with a radio transmitter which directly emits a signal to a police station or other security authority. It is conceivable to accommodate a corresponding radio transmitter in the housing 300 and to connect the alarm line AL to the radio transmitter. This can emit a radio signal via an externally arranged antenna.

It is also conceivable to emit an optical or acoustic signal in the event of a detected attempt at damage or theft. The theft monitor 40 may also include a sensor that monitors the supply voltage on the supply line SV. In the event of a sudden drop in a supply, for example by severing the supply line SV, an alarm signal can be generated independently of an external supply.

Figure 2 shows a schematic embodiment of an embodiment of the theft monitoring device, which is coupled to one or more solar modules. These form a social lars trang. The theft monitoring device comprises an input 400 for a control signal KS. The control signal KS is advantageously a logical signal with a random data content. However, it is not limited to a logical or digital signal, but may also be an analog signal.

For example, such a randomness can be achieved by a correspondingly long feedback shift register which is filled with a random initial value.

The initial value may include a time signal, a temperature value, a voltage value or another as random signal as possible. The control signal KS is expediently provided by a circuit which is accommodated within the housing of the theft monitoring device. Preferably, the circuit for providing a control signal forms part of the theft monitoring device.

The input 400 is connected to a control input of a switch

420 connected. The control signal KS controls the switch 420 between an open and a closed state. The switch 420 serves to connect a power source 410 to one of the terminals 42. The constant current source 410 is fed by the voltage supply line SV and generates a substantially constant current signal. If the switch 420 is closed, a low current flows via the terminal 42 via the series-connected solar modules of the solar string 20b. Each individual solar module drops a slight voltage, for example, of the order of 0.5 V per solar cell. From this, it is possible to determine a total voltage which has to be provided via the two connection terminals. The correction signal KS is also supplied to a delay circuit 440, which delays the signal with an adjustable delay time. On the output side, the delay circuit 440 is connected to an input of a comparison circuit 450. This comprises a logic gate 455 with two inputs, which in the present case also simultaneously form the inputs of the comparison circuit. The second input of the logic gate 455 is coupled to the second terminal 42. At this also the final shunt 4 is connected, which is connected to ground.

In the operation of the theft monitoring device, a signal of the terminal 42 and thus the solar strand 20b is now supplied with the aid of the control signal, which has the same time course as the signal applied to the input control signal KS. Due to the propagation delay through the solar string 20b, however, a time offset between the control signal at the input 400 and the signal generated by the current source 410 and the switch 420 occurs. The time delay is determined in a calibration phase and compensated by the additional delay circuit 440. The two signals, preferably with logic levels, are fed to gate 455, which logically combines them.

In a theft attempt, for example, removal of one of the modules of the solar string 20b, the series connection is interrupted and there is a temporal change in the two signals supplied to the gate.

Figure 4 shows such a course, in which at the time Tl a module is removed from the solar strand. The control signal KS is a pulse sequence, shown in this diagram for reasons of clarity as a periodic rectangular success. Accordingly, the passing through the solar modules monitoring signal is also a rectangular sequence. Changes in the flanks of the monitoring signal emitted by the solar string 20b are compensated again by signal-processing measures, so that the monitoring signal US has the same course. The above-mentioned time delay between the signals KS and US is not shown in this example.

At time Tl or shortly before a corresponding solar module is removed from the strand. This results in an interruption of the monitoring signal to a logic low level, whereby the signal RS output from the logic XOR gate 455 switches between logic levels.

As an alternative, it is also advisable to connect a holding circuit downstream of the logic gate, for example in the form of a flip-flop. This then generates a continuous alarm signal, even if, after a short time, the monitoring signal again changes to a normal state, for example due to a manipulation attempt.

Such a circuit can also be expanded to the extent that the short-term disturbances caused by external accidental influences are detected and they do not trigger an alarm. This reduces the number of possible false alarms. For example, the logic gate 455 may be followed by a circuit which responds to a change in the level of the signal RS after some time and thus checks whether during this period of time Signal RS returns to the original value. If this is the case, a disturbance is perceived as accidental and not as a manipulation attempt. If, on the other hand, the signal RS remains in an alternating state over an extended period of time as shown in FIG. 4, this is recognized as a theft or damage attempt and a corresponding alarm is triggered by the circuit connected to the gate 455.

The theft monitoring device according to FIG. 2 also has a voltage detection device. This serves to detect manipulation attempts, for example, by bridging the two terminals 42 effectively and also to provide a corresponding alarm signal in such. For this purpose, the theft monitoring device 40 includes a comparison circuit 430, which is connected to a first input to the switch 420 and the terminal 42. A second input leads in this embodiment to a voltage divider 435 to which a reference signal Uref is supplied. The voltage detector 430 is designed such that it detects the maximum voltage when the switch 420 is closed and compares it with the divided reference voltage Uref applied to its second input. The comparison circuit can also be designed as a window discriminator with an adjustable reference threshold.

Taking into account only the maximum voltage when switch 420 is closed has the advantage that the control signal can be a randomly logic signal alternating between two states, which opens or closes switch 420. The comparator 430 is designed so that a comparison only when closed Switch 420 is performed. For example, the comparator 430 may be designed for this purpose with the signal input 400 for the supply of the control signal KS, so that the control signal KS is activated or deactivated in accordance with its level.

In a manipulation attempt, the voltage applied to the first input of the comparator 430 now changes, at least in the short term, thus leading to a signal change in the output signal of the comparator 430. The output of the comparator 430 is connected to a second gate 456, which in the present case is a logical OR Gate is executed. Also after the logical OR gate one of the above-described holding circuits may be provided. In a tampering attempt, either by removing one of the

Solar modules or bridging the two terminals thus one of the two monitoring signals is changed, so that the logic gate 456 emits a corresponding alarm signal at the output 457.

The anti-theft device 40 shown in FIG. 2 generates an alarm signal upon a corresponding voltage or current change caused by a damage or manipulation attempt of the connection terminals 42 and the solar modules of the latter arranged between them

Stranges 20b. The theft monitoring device can also be implemented with additional sensors so that further parameters can be monitored. For example, it is also possible to monitor the current flowing through the terminals 42. Such a circuit may be connected in the signal path between terminal 42 and switch 420. This derives a signal from the flowing current, for example by means of a current mirror, and compares it in one Comparator with a reference signal. If the current changes due to a manipulation attempt, this causes a change of the mirrored current and thus of the derived signal. An alarm will then be triggered.

In addition, it is possible based on the existing alarm signals, for example, by the comparator 430 or the gate 455 close to the manner of a possible manipulation attempt back.

Figure 3 shows an embodiment of a theft monitoring device for a simple electrical load, which is connected to the two terminals 42b and 42a. In this embodiment, the voltage dropping across the load as well as the current flowing through the load is relatively low. It should be noted that, for example, in the case of a theft device for a plurality of solar modules, a high-voltage source may be required in order to cope with the large voltage drop across the solar modules. The theft monitoring device 40 has an input 400 for supplying the control signal KS. As shown, the input 400 is, on the one hand, connected directly to a logic XOR gate 455 and, on the other hand, to the base terminal of a bipolar transistor T50.

The bipolar transistor T50 acts as a switch and is arranged in series with two resistors S51 and S50 forming a voltage divider between a supply terminal VS and a ground terminal GND. A node between the two resistors S50 and S51 leads to the base terminal of a bipolar transistor. The transistor T50 and transistor T420 circuit form switch 420. Transistor T420 drives a constant current source 410, which in the present case comprises the elements R2, D40 and D41, R4 and T4.

In detail, the transistor T420 of the switch 420 is connected on the emitter terseitig to the supply terminal VS and the collector side to a node between the resistor R2 and the Zener diode D40 and to the base of the transistor T4. The resistor R2, Zener diode D40 and D41 form a series circuit and are connected between the supply terminal US and the ground terminal GND and serve to bias the constant current source 410. The transistor T4 is with its emitter terminal to the element R4 and collector side with the output and the Connection terminal 42b connected.

Also connected to the terminal 42b is a comparator 430 whose second input is supplied with a reference potential Uref. The comparator 430 is used to monitor the voltage drop across the load between the two terminals.

The theft monitoring device further includes a comparator OP whose first inverting input is connected via a resistor R3 to the second terminal 42a. In its second non-inverting input, a voltage signal is supplied, which is adjustable via a variable resistor R4. The variable resistor R4 is arranged in series with a resistor R1 in series between the supply terminal VS and the ground terminal GND. It serves to generate a variable voltage signal and deliver it to the comparator. In this way, with a pulsed or approximately square-wave-shaped or logical signal applied to the connection terminal 42a, the changeover time and thus the edge steepness can be improved. be sert. The output of the amplifier OP is connected to the second input of the logic gate 455.

The Zener diode D6 connected between the ground potential and the output terminal of the differential amplifier OP and the resistor S6 between the output terminal of the differential amplifier and the supply terminal VS serve to stabilize the output signal to provide the necessary current.

The output of the gate is connected via a low-pass filter TP formed of a resistor R6 and a capacitor C6 via a further resistor R7 to the base of an output transistor T7. The collector of the transistor T7 forms the output terminal 457, at which the output signal RS can be tapped.

During operation of the theft monitoring device, a pulsed, preferably random, rectangular control signal KS is supplied to the input 400. This can also be a logical signal, so switch between two levels. The control signal KS controls the transistor T50 in such a way that correspondingly the switching transistor 420 of the constant current point 410 provides a corresponding square-wave current signal at the collector output of the transistor T4. The over the

Load dropping voltage is compared with the comparator 430 with a reference voltage. At the same time, the current flows through the load arranged between the terminals 42a and 42b.

Due to possible changes in the current signal, for example a flattening of the flanks, the signal flowing via the device arranged between the terminals 42b and 42a must be detected. be recycled. For this purpose, the differential amplifier OP, which sets, among other things set by the variable resistor R4, the necessary slope and the appropriate switching point. The amplifier OP serves at the same time to provide the required logic level for the downstream gate 455. The signal quality is further improved by the Zener diode D6 and the resistor S6.

Due to the different switching elements of the theft monitoring device 40 and the electrical load between the two terminals, there may be a propagation delay between the processed signal at the output of the differential amplifier OP and the control signal KS, which is supplied to the two inputs of the logic XOR gate 455. Since this is intended to detect a temporal change in the pulse sequence, a propagation delay in one of the two signal paths leads directly to a corresponding signal. This unintentional propagation delay, which represents no manipulation attempts, is corrected by the subsequently adjustable low-pass filter TP with the capacitance-variable capacitor C6 and the resistors R6 and R7.

With a longer propagation delay caused by a manipulation attempt in the consumer, the logic XOR gate also responds and produces at the output a logic high level, which is supplied to the base of the output transistor T7. The corner frequency of the low-pass filter is selected so that a pulse sequence characterizing the manipulation attempt is not suppressed by the low-pass filter TP. In the case of the theft monitoring device according to the invention, an object to be monitored is thus switched into a signal path. A preferably randomly alternating signal is sent via the signal path, and a change in the time profile between the two signals is determined with a corresponding reference signal. In a detection of a temporal change in the signal curve, a tampering attempt or a damage attempt of the object can be concluded, for example, on a manipulation attempt.

The theft monitoring device is particularly suitable if the object to be monitored is itself an electrical device, for example a light source or a power generator such as a solar module, a solar cell or a plurality of such elements. The theft monitoring device can be easily accommodated in the housing and integrated into existing systems. The theft monitoring device can be housed in particular in the housing or space of the inverter, which is particularly protected against manipulation attempts. In particular, the theft protection or monitoring in existing systems can be easily retrofitted.

Reference sign list

SV power supply line

Sl, S2 power lines

AL alarm line

Uref reference voltage

4 final shunt

10 inverters

20a, 20b solar strand

30, 40 theft monitoring device

42 switches

50 sensor monitoring device

52 sensor

300 housing

310 board

400 signal input

410 power supply

420 switches

430 comparators

435 voltage divider

440 delay circuit

450 comparison circuit

455, 456 logic gates

457 exit

T420, T4, T50 bipolar transistors

T7 output transistor

OP differential amplifiers

R4 adjustable resistance

R1, R2, R4 resistance

R4, R6, R7 resistance

D40, D41, D6 tens diodes

C6 capacitor

TP low pass

Claims

claims

1. Theft monitoring device, in particular for one or more solar modules, comprising: - an input (400) for supplying a time-varying control signal (KS); two terminals (42, 42a, 42b) adapted to be coupled to an anti-theft device (20a, 20b), in particular one or more solar modules; a switch (420) controlled by the control signal for supplying a monitoring signal at one of the connection terminals (42, 42b); - A comparison circuit (455) coupled to the input (400) and with the other of the terminals (42, 42 a) and is adapted to detect a change in a time course between the control signal and the monitoring signal.

2. Theft monitoring device according to claim 1, wherein the control signal (KS) has a rectangular shape.

3. Theft monitoring device according to one of claims 1 to 2, wherein the control signal (KS) has a temporally randomly changing amplitude or logic level.

The antitheft monitor of any one of claims 1 to 3, further comprising: - a controllable current source (410) including the switch (420) for delivering a current to the one terminal (42, 42b) in response to the control signal (KS).

5. Theft monitoring device according to one of the claims

1 to 4, in which the comparison circuit (450) comprises at least one element (455) for logic operation, which is coupled on the input side to the input (400) and to the other of the connection terminal (42, 42a).

The anti-theft device of claim 5, wherein the comparison circuit (450) comprises at least one of an XOR, a NAND, or a NOR gate.

7. Anti-theft device according to one of claims 1 to 5, further comprising: a delay circuit (440) for compensating a caused by the device to be monitored (20a, 20b) propagation delay of the monitoring signal (US).

8. Theft monitoring device according to claim 7, wherein the delay circuit comprises a filter (TP) which is connected to an output of the comparison circuit (450, 455).

9. Anti-theft device according to claim 8, wherein the filter (TP) is an adjustable low-pass filter.

The anti-theft device of claim 7, wherein the delay circuit (440) comprises a number of delay elements arranged between the input (400) and the comparison circuit (450).

11. Anti-theft device according to one of claims 1 to 10, further comprising: a voltage detector (430), the input side to one of the terminals (42, 42 b) and coupled to a Comparison of one of the terminals (42, 42b) voltage applied to a reference value (Uref) is formed.

12. Anti-theft monitoring device according to one of claims 1 to 11, further comprising: two switches whose first terminals form the terminals (42), and whose second terminals are connectable to an inverter (10).

13. Theft monitoring device, in particular for one or more solar modules, comprising: an input (400) for supplying a time-varying control signal (KS); - A voltage connection (SV, VS) to which a controllable current source (410) is connected, which outputs a signal to one or more devices to be monitored (20a, 20b) in response to the control signal (KS); a comparison circuit (450, 455) which compares a signal processed by the device (s) to be monitored with the control signal (KS) and responds to a change in a time profile between the control signal (KS) and the processed signal.

14. Theft monitoring device according to claim 13, wherein the device comprises one or more solar cells, which are connected in the flow direction.

15. Anti-theft monitoring device according to one of claims 13 to 14, wherein the control signal (KS) comprises a time-varying amplitude or pulse train.

16. Anti-theft monitoring device according to one of claims 13 to 15, further comprising: a voltage detection device (430) which is configured to compare a voltage dropping across the device or devices to be monitored with a reference voltage (Uref) and one by a manipulation attempt on the or to detect changes in the falling voltage caused to the devices.

17. Anti-theft device according to claim 16, wherein the comparison circuit (450, 455) is configured to respond to a change in a time course or a signal of the voltage detection device (430).

18. Anti-theft monitoring device according to one of claims 13 to 17, wherein the theft monitoring device is arranged in a housing (300) which is provided with an alarm mechanism (AL) for protection against unauthorized opening.

The antitheft monitor of any one of claims 13 to 18, further comprising: a delay circuit (440) arranged to compensate for a delay difference between the signal processed by the one or more devices to be monitored and the control signal (KS).

20. A method for monitoring an electrical device, in particular a solar module, comprising: - providing a time-varying control signal (KS);

Generating a monitoring signal derived from the control signal; Supplying the monitoring signal to the electrical device and detecting the signal output from the device;

Determining a change in the timing of the signal delivered by the device; - generating an alarm signal in response to a change.

21. The method of claim 20, wherein determining a change comprises: comparing the signal delivered to the device with the time-varying control signal.

22. The method according to any one of claims 20 to 21, wherein the time-varying control signal (KS) is a logical, in particular randomly changing signal with two different levels.

A method according to any one of claims 20 to 22, wherein the step of determining a change comprises: - compensating a delay difference between the signal output by the device and the control signal by:

Filtering a signal representing the change over time or;

Delaying the control signal by a time corresponding to the propagation delay.

24. The method according to any one of claims 20 to 23, wherein a monitoring current is supplied to the electrical device, wherein the monitoring current is generated by controlling a current source with the control signal.

25. The method according to any one of claims 20 to 24, further comprising: Detecting a voltage drop across the electrical device and;

Comparing the detected voltage with a reference value; Generating an alarm signal in response to the comparison.