Method for detecting incorrect positioning of a sensor

Abstract

The invention relates to a method for detecting incorrect positioning of a first sensor (2; 102) in a physical system (6; 106), wherein the first sensor (2; 102) is designed to provide a first sensor signal which is representative of a first state variable of the physical system (6; 106) at a first position in the physical system (6; 106), wherein the physical system (6; 106) has a second sensor (22; 122) which is arranged at a second position in the physical system (6; 106) and provides a second sensor signal which is representative of a second state variable of the physical system (6; 106), wherein the second position is different from the first position and the first state variable and the second state variable are interdependent on one another. The method comprises the following steps: a) receiving the first sensor signal provided by the first sensor (2; 102) over time, b) receiving the second sensor signal provided by the second sensor (22; 122) over time, c) determining a difference between the first sensor signal and the second sensor signal over time, d) determining an interdependency characteristic variable of the determined difference, e) comparing the determined interdependency characteristic variable with a predefined interdependency limit value, and f) detecting incorrect positioning of the first sensor (2; 102) in the physical system if the interdependency characteristic variable exceeds the predefined interdependency limit value.

Description

[0001] Method for detecting incorrect positioning of a sensor

[0002] The invention relates to a method for detecting incorrect positioning of a sensor in a physical system. The physical system can be configured, in particular, as a heating system, in particular as a domestic water heating system, as used in a habitable vehicle. The habitable vehicle can be, in particular, a caravan or similar vehicle, such as a mobile home (motorized caravan), a caravan, a camper van, a construction trailer, a residential container, or a sales van. Furthermore, the term "habitable vehicle" is intended to include boats and ships that can provide mobile accommodation.

[0003] In today's heating systems used in habitable vehicles, to detect whether the respective temperature sensors used in the heating system are functioning properly (also called plausibility checks or plausibility checks), their sensor signals are checked to determine whether they lie within a previously defined valid value range or within an invalid value range outside the valid value range. In this way, for example, a sensor open circuit or a short circuit in a sensor can be detected. If a sensor signal or its values ​​lie within the invalid value range, the associated sensor is identified as faulty and a replacement is initiated and / or the sensor signal from a redundant, second sensor is used instead.

[0004] DE 10 2011 084 784 A1 discloses a method for verifying the plausibility of a sensor signal, wherein a first sensor element detects a first physical quantity and outputs it as a first sensor signal, and a second sensor element detects a second physical quantity correlated with the first physical quantity and outputs it as a second sensor signal. The first sensor element has a reliability range with an upper limit and / or a lower limit, which is related to the second physical quantity detected by the second sensor element. A current value of the first physical quantity detected by the first sensor element is recognized as plausible if a current value of the second physical quantity detected by the second sensor element lies within the reliability range of the first sensor element.

[0005] EP 3 390 967 B1 discloses a method for monitoring two redundant sensors arranged in a chemical plant or in an aircraft. A first sensor provides a first sensor signal, and a second sensor provides a further sensor signal. A second derivative is generated from the first sensor signal as the first analysis signal. Correspondingly, a second derivative is generated from the further sensor signal as the further analysis signal. A temporal horizon for the sensor signals is then selected by comparing the generated analysis signals with a predefined limit for the scatter, stationarity, and dynamics of the sensor signal. The temporal horizon contains a minimum number of data points characterized by a second temporal derivative whose absolute value lies above a predefined dynamic limit of the second derivative.A correlation between the analysis signals from the first and the second sensor is determined over the time horizon and compared with a permissible correlation range. Alternatively, a difference is compared with a permissible difference range. Depending on the comparison result, it is determined whether one of the two redundant sensors is faulty.

[0006] When checking the sensor signals to see whether they are within a valid value range, incorrectly positioned sensors are often not detected. Incorrect positioning can occur, for example, in the event of a strong shock or material fatigue, which has caused the sensor to move out of its correct position. For example, if a temperature sensor has a valid value range of -20°C to 80°C and, due to incorrect positioning, it currently measures 40°C, even though it should output a higher temperature due to the current state of the heating system, the incorrect positioning would not be detected if the sensor signal were simply checked to see whether it is within the valid value range. According to the DIN standard EN 60335-2-21, which defines special requirements for hot water heaters / domestic water heating systems, the water temperature at the outlet, i.e.During withdrawal / drawing, a specified maximum value must not be exceeded for safety reasons, even in the event of a defective or incorrectly positioned temperature sensor. Therefore, during the approval process for domestic hot water heating systems, the temperature sensors are typically set to a fixed sensor signal value, and a check is carried out to determine whether overheating is prevented by the safety switches (also called protective temperature limiters) provided in the heating system. However, incorrect positioning of a temperature sensor cannot be detected in this way.

[0007] The object of the invention is to provide a method and a device for detecting incorrect positioning of a sensor in a physical system. The physical system is, in particular, a heating system, preferably a domestic hot water heating system, which can be used in a habitable vehicle.

[0008] The object is achieved by a method for detecting an incorrect positioning of a sensor having the features of claim 1 and by a device for data processing having the features of claim 10.

[0009] The invention relates to a method for detecting an incorrect positioning of a sensor in a physical system. The sensor is referred to below as the first sensor and is designed to provide a first sensor signal that, when the first sensor is positioned at a first position in the physical system, is representative of a first state variable of the physical system. This first position represents the proper, correct position of the first sensor in the physical system.

[0010] The physical system comprises a second sensor. The second sensor is arranged or can be arranged at a second position in the physical system. The second position corresponds to the correct and thus correct position of the second sensor in the physical system. At the second position, the second sensor outputs a second sensor signal representative of a second state variable of the physical system. The second position at which the second sensor is arranged is different from the first position at which the first sensor is to be arranged.

[0011] The second state variable, which the second sensor detects, and the first state variable, which the first sensor is intended to detect, interact with each other. In particular, there is a correlational relationship between the first state variable and the second state variable. Preferably, there is also a causal relationship between the first state variable and the second state variable.

[0012] The inventive method for detecting incorrect positioning of the first sensor comprises the following steps: In a first step, a first sensor signal output by the first sensor is received over time, and in a second step, a second sensor signal output by the second sensor is received over time. The first step and the second step are preferably performed simultaneously, but can also be performed one after the other in any order.

[0013] In a subsequent step, a difference between the first sensor signal and the second sensor signal is determined over time. This means that the difference between the temporal profile of the first sensor signal and the temporal profile of the second sensor signal is calculated. In a subsequent step, an interaction parameter is calculated from the determined difference. The interaction parameter is a measure of the interaction between the first sensor signal and the second sensor signal (or the variables presumably represented by the sensor signals).

[0014] In a subsequent step, the determined interaction parameter is compared with a predefined interaction threshold. The predefined interaction threshold can be stored in a processor of a data processing device provided in the physical system. Finally, in a subsequent step, an incorrect positioning of the first sensor in the physical system is detected if the interaction parameter exceeds the predefined interaction threshold.

[0015] The respective steps of the method can be executed by the data processing device provided in the physical system or by its processor, which is designed, for example, as a control and evaluation unit. This means that the method according to the invention is designed, in particular, as a computer-implemented method, which is implemented in a processor of a data processing device and can be executed by the processor.

[0016] According to a preferred embodiment, the interaction parameter is determined continuously over time, so to speak, in a sliding manner. In this embodiment, an incorrect positioning of the first sensor is only detected when the interaction parameter exceeds the predefined interaction threshold for a predetermined time interval (i.e., for the entire duration of the predetermined time interval). The predetermined time interval can be stored in the processor of the data processing device.

[0017] According to a particularly preferred embodiment, the interaction parameter is the variance of the difference between the first sensor signal and the second sensor signal. This variance is preferably determined using the so-called Welford algorithm (see, for example, https: / / jonisalonen.com / 2013 / deriving-welfords-method-for-computing-variance / , https: / / en.wikipedia.org / wiki / Algorithms_for_calculating_variance and https: / / en.wikipedia.org / wiki / Algorithms_for_calculating_variance#Online_algorithm). The Welford algorithm is a so-called "one-pass" algorithm, i.e., an algorithm with which the variance can be calculated in a single calculation step.When using the Welford algorithm, it is not necessary to calculate the mean of the measured values ​​in a first calculation step and then to determine the variance from the measured values ​​and their mean in a second calculation step, whereby the measured values ​​would have to be temporarily stored for the second calculation step. Instead, the Welford algorithm can advantageously calculate the variance in a single calculation step, which saves storage space. Furthermore, the Welford algorithm is characterized by high numerical stability and robustness and is not very susceptible to catastrophic cancellation. Of course, it is also possible to calculate the variance in other ways, for example by means of numerical differentiation, using an algorithm with two calculation steps, or by using a physical model in combination with a state observer.

[0018] When using the method according to the invention, the use of two identical, redundant first sensors can advantageously be dispensed with. To detect incorrect positioning of a first sensor, it is sufficient to perform a comparison with a sensor signal from a second sensor already provided in the physical system. This allows for savings in installation space, weight, and costs. The safety switch can be dispensed with in the approval procedure described above.

[0019] The physical system in which the method according to the invention is used is preferably designed as a heating system. The heating system comprises a fluid circuit with a fluid container. A heating device is assigned to the fluid circuit. The first sensor is designed as a first temperature sensor, which can be arranged in and / or on a (flow) path (fluid path) leading from the heating device to the fluid container, in particular on a corresponding fluid line, of the fluid circuit. This means that the first sensor is intended to detect the temperature in the fluid flowing from the heating device to the fluid container. The second sensor is designed as a second temperature sensor. The second sensor is assigned to the heating device or, in an alternative heating system, to the fluid container.The first and / or the second temperature sensor can, for example, each be designed as an immersion sensor with an immersion sleeve as the sensor housing and a sensor probe if they are intended to measure the temperature of a fluid. When properly installed, the respective sensor probe comes into thermal contact with the fluid. The sensor housing itself does not come into contact with the fluid. In a heating system which is designed as a domestic water heating system for a habitable vehicle, the second sensor is assigned to the heating device according to a preferred embodiment. The heating device comprises in particular a heating unit and a heat exchanger which is designed to transfer heat generated by the heating unit to the fluid in the fluid circuit. The second sensor is preferably assigned to the heat exchanger, in particular installed in and / or on it. The fluid is domestic water.The heating unit preferably comprises a flame tube and a burner, which is fed with a fuel such as liquefied petroleum gas, diesel, or gasoline. The first sensor, designed as a first temperature sensor, is preferably arranged at or at least near a fluid outlet / hot water outlet of the fluid circuit / water circuit, via which water heated by the heating device is fed into the fluid container.

[0020] According to an alternative embodiment of the heating system, the heating device comprises one or more thermal solar collectors. In this embodiment, the first sensor, designed as a first temperature sensor, is also arranged in the (flow) path of the fluid from the heating device (here: the one or more thermal solar collectors) to the fluid container. In this embodiment, the fluid is solar fluid (also called solar medium). The fluid container is designed as a buffer storage tank, in which the solar heat stored by the solar fluid is transferred to domestic water by means of heat exchange. This water can, for example, flow through underfloor heating or be used for showering and washing.

[0021] A further aspect of the invention relates to a data processing device comprising a processor, in particular a microprocessor, configured to execute the steps of the method according to the invention. The data processing device (hereinafter also referred to as data processing device) can, for example, be a control and evaluation unit provided in the physical system, which may be configured, for example, as a heating system. The invention is explained in more detail below with reference to the accompanying drawings. In the drawings:

[0022] Figure 1 is a schematic representation of a correctly positioned sensor (Figure 1A) and an incorrectly positioned sensor (Figure 1B),

[0023] Figure 2 is a schematic representation of a first embodiment of a physical system with a correctly positioned first sensor (Figure 2A) and with an incorrectly positioned first sensor (Figure 2B),

[0024] Figure 3 is a flow chart of the method according to the invention,

[0025] Figure 4 is a curve diagram with exemplary curve profiles of a first sensor signal, a second sensor signal and a variance and

[0026] Figure 5 is a schematic representation of another embodiment of a physical system with a correctly positioned first sensor.

[0027] The same reference symbols indicate the same and / or equivalent components.

[0028] Figure 1A shows a sensor 2, which is embodied, for example, as a temperature sensor. The sensor 2 is arranged in or on a path 4 of a water circuit leading to a partially shown water container 1 (also called a water tank), via which heated water is supplied to the water container 1, and serves to detect the temperature of the supplied water. The sensor 2 can be embodied, for example, as an immersion sensor. The path 4 is designed, in particular, as a fluid line in the form of a pipeline. The sensor 2 corresponds to a first sensor, the water container 1 to a fluid container, and the water circuit to a fluid circuit within the meaning of the invention. The same applies to Figure 2 described below.

[0029] Figure 1A shows the correct arrangement of sensor 2, in which the (first) sensor signal provided by sensor 2 represents a (first) state variable, namely the temperature of the water conducted in path 4. Figure 1B corresponds to Figure 1A, but with an incorrectly positioned sensor 2. In Figure 1B, sensor 2 is no longer positioned on or in path 4, but is incorrectly positioned at a distance from path 4. For example, sensor 2 may have become detached / moved out of the correct position shown in Figure 1A due to incorrect positioning during assembly or vibration or material fatigue during operation. In the incorrect position shown in Figure 1B, the (first) sensor signal provided by sensor 2 is no longer suitable to represent the (first) state variable / the water temperature in path 4.

[0030] Figure 2 shows an embodiment of a physical system, according to which the physical system 6 is designed as a heating system. The heating system 6 can be installed in a habitable vehicle and serves to provide warm water for use by a user, for example, during showering and washing processes.

[0031] The heating system comprises a fluid container in the form of a water container 1, which corresponds to the water container in Figure 1. The water container 1 is arranged in a fluid circuit designed as a water circuit 8. Upstream of the water container 1, a heating device 11 is assigned to the water circuit 8. The heating device 11 comprises a heat exchanger 12 and a heating unit (not shown), which is preferably arranged within the preferably cylindrical heat exchanger 12. The cylindrical heat exchanger 12 can have a square or circular cross-sectional area. The heating unit preferably comprises a flame tube and a burner, which is fed with a fuel such as liquefied gas, diesel, or gasoline. Additionally or alternatively, the heating unit can comprise electrical heating elements (not shown), which can be designed in particular as heating rods and integrated into the heat exchanger 12.

[0032] The water circuit 8 has a fresh water inlet 14 upstream of the heating device 11, through which fresh water to be heated can be fed. By means of a pump 18 arranged in the water circuit 8 between the fresh water inlet 14 and the heating device 11, the water is passed through the heating device 11, in particular its heat exchanger 12. Water lines / pipes (not shown) through which the water is passed for heating are preferably integrated into the heat exchanger 12. This results in a heat exchange with the heat generated by the heating unit. Furthermore, water located in the water tank 1 can be passed through the heat exchanger 12 for reheating by means of the pump 18. The warm water can then be drawn off ("tapped") by the user via a warm water outlet 16 provided on the water tank 1, for example a tap.

[0033] To detect the temperature for setting the hot water temperature, the heating system 6 has a first sensor 2, which corresponds to the single sensor shown in Figure 1 and the first sensor of the invention. In the exemplary embodiment shown, the first sensor 2 is designed as a temperature sensor. When correctly positioned, the first sensor 2 is arranged in and / or on a (flow) path 4 of the water circuit 8 leading from the heating device 11 to the water tank 1, in particular at its water tank-side end, which forms a hot water outlet (not designated in more detail) into the water tank 1. This is shown in Figure 2A. Furthermore, a second sensor 22 is provided, which is also designed as a temperature sensor and is assigned to the heating device 11, in particular its heat exchanger 12. The second sensor 22 is preferably installed in or on the heat exchanger 12.

[0034] The first sensor 2 outputs a first sensor signal which, when the first sensor 2 is correctly positioned, is representative of the water temperature in path 4, i.e., the water temperature shortly before or upon exiting path 4 into the water tank 1. This water temperature is also referred to below as the water outlet temperature and represents a first state variable of the heating system 6. The second temperature sensor 22 outputs a second sensor signal which is representative of the temperature of the heat exchanger 12 (also called heat exchanger temperature). Correct positioning of the second sensor 22 is assumed. The heat exchanger temperature detected by the second sensor 22 represents a second state variable of the heating system 6.

[0035] The water outlet temperature (first state variable) and the heat exchanger temperature (second state variable) interact with each other. There is a causal relationship between the heat exchanger temperature and the water outlet temperature. The water outlet temperature, in particular, depends on the heat exchanger temperature. If the first sensor 2 and the second sensor 22 are correctly positioned, there is therefore also an interaction between their respective sensor signals, in this case a causal relationship. If the first sensor 2 and the second sensor 22 each output voltage values, and the second sensor signal representing the heat exchanger temperature increases by, for example, 1 volt, then if the first sensor 2 is correctly positioned, the first sensor signal representing the water outlet temperature will increase with a time delay by a specific, possibly reduced / damped voltage value.However, this is not to be expected if the first sensor 2 is incorrectly positioned. Since the second temperature sensor 22 is installed in the heat exchanger 12, incorrect positioning of the second temperature sensor 22, particularly due to vibration and faulty installation, can generally be ruled out or is at least unlikely.

[0036] Figure 2B shows the heating system 1 illustrated in Figure 2A, but with the first sensor 2 incorrectly positioned (corresponding to Figure 1B). The first sensor 2 has become loose from its correct position, for example, due to material fatigue or vibration, or due to incorrect installation during a repair during its service life. This can result in the sensor signal detected by the first temperature sensor 2 no longer being representative of the water outlet temperature (the first state variable).

[0037] The sensor signals provided by the temperature sensors 2, 22 are transmitted for evaluation via signal lines (not shown) to a data processing device 24, in particular to a control and evaluation unit, which contains a processor (not shown) that executes the method according to the invention. The data processing device 24, in particular its processor, is further configured to control the heating device 11 and / or the pump 18 via corresponding signal lines (not shown) depending on the first sensor signal and / or the second sensor signal in such a way that a specific target water temperature can be set.

[0038] Figure 3 shows a flowchart of the method according to the invention. As mentioned, the method according to the invention, or its method steps, can be executed by the data processing device 24. The method according to the invention is used, for example, in the heating system 6 shown in Figure 2. In step 10 of the method according to the invention, a first sensor signal from the first sensor 2 is received over time. In step 20, a second sensor signal from the second sensor 22 is received over the (same) time. Steps 10, 20 preferably run simultaneously / in parallel.

[0039] In order to increase the stability of the first sensor signal and the second sensor signal (or of their values) and to reduce the influence of noise and other external disturbances, also for reasons of electromagnetic compatibility, the first sensor signal and preferably also the second sensor signal are preferably smoothed in steps 10 and 20 after their reception, for example by low-pass filtering, exponential smoothing and / or moving averages of their arithmetic values ​​(moving average).

[0040] Figure 4 shows, as a dotted curve, an example of the first sensor signal, which is representative of the water outlet temperature when the first sensor 2 is correctly positioned, over time. The dash-dotted curve in Figure 4 shows an example of the second sensor signal, which is representative of the heat exchanger temperature.

[0041] In the subsequent step 30, the difference between the sensor signals received in steps 10, 20 is calculated over time. In the subsequent step 40, an interaction parameter is determined from the difference. The interaction parameter is preferably the variance of the difference, which is advantageously calculated using the Welford algorithm, which enables a time- and memory-efficient calculation. In Figure 4, the variance of the difference between the first and second sensor signals shown in Figure 4—determined continuously according to a preferred embodiment—is shown as a dashed line.

[0042] In the subsequent step 50 of the method according to the invention, the interaction parameter (in this case: the variance) is compared with a predetermined interaction limit (in this case: variance limit). In the example in Figure 4, the variance limit is 7040. If it is determined in step 50 that the variance does not exceed the variance limit, the method begins again (path "no" branching off from step 50 in Figure 3). If, however, it is determined in step 50 that the variance exceeds the variance limit (path "yes" branching off from step 50), it can be concluded that the first temperature sensor 2 is incorrectly positioned.

[0043] In order to keep the influence of outliers in the values ​​of the first and / or the second sensor signal as low as possible, the preferably continuously determined interaction parameter / variance should exceed the interaction limit value / variance limit value for a specific time interval, i.e. for a specific number of consecutive discrete measuring / sampling times, before an incorrect sensor positioning is detected. This is indicated in Figure 3 by step 60. Only when it is determined in step 60 that during a predetermined time interval T the interaction limit value / variance limit value was always exceeded by the respectively determined interaction parameter / variance (path "yes" branching off from step 60), an incorrect positioning of the first sensor 2 is detected in the subsequent step 70.If, however, it is determined in step 60 that the interaction limit / variance limit was not exceeded during the entire time interval T (path "no" branching from step 60), the method returns to steps 10 and 20 and begins again. For example, if the specified time interval is 60 seconds, the variance limit of 7040 is exceeded at least in the range from 500 to 600 seconds during T = 60 seconds in the exemplary curves shown in Figure 4, thus detecting incorrect positioning of the first sensor 2.

[0044] If incorrect positioning of the first sensor 2 is detected in step 70, the physical system configured as the heating system 6 is preferably brought into a safe state, in particular switched off, by means of the control and evaluation unit 24. It is also possible to switch off only the incorrectly positioned sensor 2 and use the sensor signal of another sensor provided in the heating system, for example, the second sensor 22, for temperature control. Of course, the method according to the invention can also be used to detect incorrect positioning of the second sensor 22, in particular when the first sensor 2 is correctly positioned.

[0045] As an alternative to determining the difference in step 30 and the variance in step 40, a correlation coefficient, in particular the Bravais-Pearson correlation coefficient, can also be determined as a measure of the correlation between the first sensor signal and the second sensor signal. The correlation coefficient can be positive or negative. In this case, the magnitude of the correlation coefficient represents the interaction parameter, which is compared with an interaction threshold in the form of a correlation threshold, which is, for example, 0.5. If the magnitude of the correlation coefficient is lower than the correlation threshold, an incorrectly positioned sensor 2 is detected. However, unlike the variance, which can be calculated in a memory-efficient manner in one step using the Welford algorithm, this is not readily possible with the Bravais-Pearson correlation coefficient, which complicates online implementation.

[0046] Figure 5 shows a further embodiment of a physical system configured as a heating system 106, in which the method according to the invention can be used. In the heating system 106, the heating device is designed as one or more thermal solar collectors 111 (also called solar thermal collectors), which are integrated into a fluid circuit in the form of a solar circuit 108. A solar fluid circulates in the solar circuit 108, to which the solar heat generated by the thermal solar collectors 111 is transferred. The solar circuit 108 comprises a pump 118 for pumping the solar fluid and a buffer storage tank 101. The buffer storage tank 101 represents a fluid container within the meaning of the invention.

[0047] In the buffer tank 101, the solar fluid heated by solar heat transfers its heat to the domestic water contained in the buffer tank 101. The domestic water is supplied to the buffer tank 101 as cold water via a fresh water inlet 114 located in its lower area and leaves it via a hot water outlet 116 located in its upper area, for use, for example, for showering, washing, and / or in underfloor heating.

[0048] The buffer tank 101 is assigned a further fluid circuit 109, which is designed as a water circuit. The water circuit 109 is assigned a further pump 119 for pumping the water and a boiler 113 for heating the water circulating in the water circuit 109. If, due to the weather conditions, sufficient solar heat is not available, the water in the water circuit 109 is heated by the boiler 113 and transfers its heat to the domestic water in the buffer tank 101, thus ensuring a supply of hot domestic water even when solar heat is insufficient. To improve heat exchange with the domestic water, the sections within the buffer tank 101 in both the (first) fluid circuit 108 (solar circuit) and the further fluid circuit 109 (water circuit) are designed in a meandering / helical manner and can be considered heat exchangers.

[0049] The heating system 106 comprises a first sensor 102 configured as a first temperature sensor, which is arranged in the correct first position in and / or on the (flow) path 104 of the solar circuit 108 leading from the thermal solar collectors 111 to the buffer tank 101 and detects the temperature of the solar fluid heated by the thermal solar collectors 111 (first state variable of the heating system 106). When correctly positioned, the first sensor signal provided by the first sensor 102 represents the temperature of the solar fluid heated by the thermal solar collectors 111.

[0050] A second sensor 122 is provided in the heating system 106, which is designed as a second temperature sensor and is assigned to the buffer tank 101. The second sensor 122 is preferably arranged in the buffer tank 101 and detects the temperature of the domestic water in the buffer tank 101 (second state variable of the heating system 106). The second sensor signal provided by the second sensor 122 represents the temperature of the domestic water in the buffer tank 101. Due to the positioning of the second sensor 122 in the buffer tank 101, its second sensor signal represents the temperature of the domestic water even if the second sensor 122 has moved out of position within the buffer tank. It is therefore assumed here that the second sensor 122 is not in an incorrect position.

[0051] If the domestic water in the buffer tank 101 is heated via the thermal solar collectors 101, the temperature of the solar fluid, which is to be detected by the first sensor 102, and the temperature of the domestic water in the buffer tank 101, which is to be detected by the second sensor 122, interact with each other, in particular, they have a causal relationship. If the temperature of the solar fluid rises, the temperature of the domestic water in the buffer tank 101 also rises. This interaction also exists between the first sensor signal, which is provided by the first sensor 102, and the second sensor signal, which is provided by the second sensor 122, if the first sensor 102 is correctly positioned on or in the path 104 of the solar circuit 108. If, however, the first sensor 102 leaves its correct position, for example due to material fatigue, the interaction (here: the causal relationship) is also lost.

[0052] The method according to the invention described in connection with Figure 3 can be used to detect incorrect positioning of the first sensor 102 assigned to path 104 of the solar circuit 108. As described, a difference between the first sensor signal of the first sensor 102 and the second sensor signal of the second sensor 122 assigned to the buffer storage 101 is determined for this purpose. From the determined difference, an interaction characteristic (preferably the variance) is then determined, which is compared with a predetermined interaction limit (preferably the variance limit). Incorrect positioning of the first sensor 102 is detected if the determined interaction characteristic exceeds the interaction limit.Of course, the method according to the invention can also be used to detect an incorrect positioning of the second sensor 122 assigned to the buffer storage 101, in particular assuming correct positioning of the first sensor 102 on and / or in the path 104 of the solar circuit 108. The method can be carried out by a data processing device 124, in particular a control and evaluation unit, of the heating system 106 or by a processor of the data processing device 124.

Claims

Patent claims 1. A method for detecting an incorrect positioning of a first sensor (2; 102) in a physical system (6; 106), wherein the first sensor (2; 102) is designed to provide a first sensor signal which, when the first sensor (2; 102) is arranged at a first position in the physical system (6; 106), is representative of a first state variable of the physical system (6; 106), wherein the physical system (6; 106) has a second sensor (22; 122) which is arranged in the physical system (6; 106) at a second position and provides a second sensor signal which is representative of a second state variable of the physical system (6; 106), wherein the second position is different from the first position and the first state variable and the second state variable interact with each other, characterized by the following steps: a) receiving the signal from the first sensor (2;102) provided first sensor signal over time, b) receiving the second sensor signal provided by the second sensor (22; 122) over time, c) determining a difference between the first sensor signal and the second sensor signal over time, d) determining an interaction characteristic of the determined difference, e) comparing the determined interaction characteristic with a predetermined interaction limit value and f) detecting an incorrect positioning of the first sensor (2; 102) in the physical system (6; 106) if the interaction characteristic exceeds the predetermined interaction limit value.

2. Method according to claim 1, wherein the interaction characteristic is determined continuously over time and an incorrect positioning of the first sensor (2; 102) is only detected when the determined interaction characteristic exceeds the predetermined interaction limit value for a predetermined time interval.

3. The method according to claim 1 or 2, wherein the interaction characteristic is the variance of the difference between the first sensor signal and the second sensor signal.

4. The method according to claim 3, wherein the variance is determined by means of a Welford algorithm.

5. Method according to one of the preceding claims, wherein the physical system (6; 106) is designed as a heating system which comprises a fluid circuit (8; 108) with a fluid container (1; 101), wherein a heating device (11; 111) is assigned to the fluid circuit (8; 108), the first sensor (2; 102) is designed as a first temperature sensor which can be arranged in and / or on a path (4; 104) of the fluid circuit (8; 108) leading from the heating device (11; 111) to the fluid container (1; 101), and the second sensor (22; 122) is designed as a second temperature sensor which is assigned to the heating device (11) or the fluid container (101).

6. The method according to claim 5, wherein the first sensor (2) is arranged at a fluid outlet via which fluid heated by the heating device (11) is fed into the fluid container (1).

7. The method according to claim 5 or 6, wherein the heating device (11) comprises a heating unit and a heat exchanger (12) which is designed to transfer heat generated by the heating unit to the fluid in the fluid circuit (8).

8. The method of claim 7, wherein the heating unit comprises a burner and a flame tube.

9. The method according to claim 5, wherein the heating device (111) comprises at least one thermal solar collector and the second sensor (122) is associated with the fluid container (101).

10. A data processing device comprising a processor configured to perform the steps of the method according to any one of the preceding claims.

Images