Sensor and metering system

Abstract

The sensor (10), which is in particular a capacitive sensor (10), comprises an earthed housing (11) as a first electrode and an electrically conductive sensor element (12) in the housing as a second electrode. The sensor (10) also comprises a measurement unit (13) and an evaluation unit (14). The sensor (10) is suitable for detecting a change in a fill level of a container (2) filled with a material (20). In the event of a change in the fill level, the measurement unit (13) is configured to detect a change in the voltage applied to the sensor element (10) as a signal. The evaluation unit (14) is configured to determine a rate of change (4) of the fill level by means of the signal from the sensor (10).

Description

[0001] Description

[0002] Sensor and dosing system

[0003] A sensor, in particular a capacitive sensor, is specified. Furthermore, a dosing system, which in particular has a sensor, is specified.

[0004] One of the tasks to be solved is to provide an improved and, in particular, material-independent effective capacitive sensor as well as an improved dosing system.

[0005] These objects are achieved, inter alia, by the subject-matter having the features of patent claims 1 and 7.

[0006] According to at least one embodiment, the sensor, which is in particular a capacitive sensor, comprises a grounded housing as a first electrode and an electrically conductive sensor element as a second electrode. The sensor element can be arranged in the housing. The capacitive sensor further comprises a measuring unit and an evaluation unit. The capacitive sensor is suitable for detecting a change in the fill level of a container filled with a material. The measuring unit is designed to detect a change in the voltage applied to the sensor element as a signal when the fill level changes. The evaluation unit is designed to determine a rate of change of the fill level using the signal from the capacitive sensor.

[0007] The evaluation unit is, for example, part of the sensor. Alternatively or additionally, the evaluation unit comprises a controller. In this case, the evaluation unit is configured, for example, to calculate an absolute value of the signal, and the control unit is configured, in particular, to calculate the rate of change or a change in the signal.

[0008] In its intended use, the capacitive sensor is used, for example, in combination with the container. The capacitive sensor is designed to monitor the fill level of the container. In particular, the fill level or the change in fill level can be determined based on the voltage applied to the capacitive sensor.

[0009] The electrically conductive sensor element is, for example, an electrically conductive cable, such as a metal cable. In this case, the capacitive sensor is also referred to as a cable sensor. Alternatively, the electrically conductive sensor element is, for example, a rod, such as a metal rod or a metal plate.

[0010] The container can be a storage container in which the material is stored. It can also be an intermediate container in which the material is only held for a short time before being emptied.

[0011] For example, the material is conveyed from another container into the container and subsequently emptied from the container in order to apply the material to a surface in a controlled and uniform manner.

[0012] The material can, for example, be grit that is spread from the container onto a defined surface such as a road or a prepared subsurface. To ensure a sufficient amount of material in the container, allowing controlled emptying and minimizing the risk of overflow, it is desirable to know the container's fill level.

[0013] The capacitive sensor works in particular with a capacitive measuring principle. This means in particular that if a space between the first electrode and the second electrode fills up, that is to say in particular between the sensor element and the housing of the capacitive sensor, the capacitance of a capacitor formed by the first electrode and second electrode changes. If a voltage is now applied to the capacitive sensor, the voltage varies due to the change in the capacitance of the capacitor formed by the first electrode and second electrode. The voltage at the capacitive sensor can be measured and in particular forms a signal from the capacitive sensor. Alternatively, a current can also be measured at the sensor, which also changes with the capacitance of the sensor. In this case, the current is the measured value.

[0014] In the following, the capacitive sensor may also be referred to as a "sensor". A capacitive sensor, referred to as a "sensor" in the following, works in particular with the capacitive measuring principle and is a capacitive sensor.

[0015] The measuring unit is, for example, a voltmeter or an ammeter, with which the voltage or current at the sensor, i.e., the sensor signal, can be measured and recorded. The evaluation unit is preferably connected to the measuring unit and configured to determine a rate of change of the sensor signal from the measuring unit's signal.

[0016] The sensor described here is based on the following technical considerations, among others. The sensor signal depends not only on the fill level but also on the material properties of the material in the container. This means that different materials result in different signal values ​​from the sensor at the same fill level. The main reason for this is the different dielectric properties of different materials. The sensor must therefore be calibrated to determine the absolute fill level value. The disadvantage of this is that the calibration has to be repeated each time a different material is added to the container. Secondly, this type of calibration is prone to errors. Incorrect calibration can lead to malfunction, total standstill or even destruction of a machine in which the sensor is used.

[0017] The sensor described here utilizes the concept of determining a gradient, or a rate of change in the fill level. By determining the rate of change, the material-dependent absolute signal value of the sensor, which corresponds to the absolute fill level, can be equalized. Therefore, material properties, especially the dielectric properties of the material, are irrelevant in the container.

[0018] Advantageously, this allows for calibration of the

[0019] Sensors can be omitted from the material in the container. Only a so-called zero adjustment to the ground potential may be necessary. This can, however, be performed at the factory, for example, and advantageously does not need to be repeated.

[0020] According to at least one embodiment or at least one of the embodiments described above, the evaluation unit is configured to determine a plurality of change values ​​of the sensor signal over a plurality of time intervals. This means that the change value recorded is how the signal value changes within a specific time interval. In other words, the change value corresponds to the average gradient of the signal in a time interval, in particular in a graphical plot of the signal versus time. Preferably, a plurality of change values ​​are recorded and stored.

[0021] Furthermore, the evaluation unit is particularly configured to determine the rate of change by calculating an average from the plurality of change values. For example, the stored change values ​​are arithmetically averaged. The rate of change thus corresponds to an average over a plurality of changes in individual time intervals.

[0022] According to at least one embodiment of the method or at least one of the embodiments described above, at least 10 change values ​​are averaged to determine the rate of change.

[0023] According to at least one embodiment or at least one of the embodiments described above, the evaluation unit is configured to output a control value for a material feed rate for a transport unit, via which the container can be filled with or emptied of the material. The control value is preferably proportional to the rate of change. The control value, in particular, has a correspondence, for example a direct correspondence, to the material feed rate.

[0024] The material feed can be used to control how much material is added to or removed from the container. This allows the fill level of the container to be regulated.

[0025] The transport unit is, for example, a conveyor chain or a transport chain. Alternatively, the transport unit is, for example, a conveyor screw.

[0026] The material feed is, for example, a chain feed or a screw feed.

[0027] It is possible for the container to be merely an intermediate container into which material is fed and removed. In this case, it is possible for there to be a first transport unit with a first material feed, via which material is fed to the first container, and a second transport unit with a second material feed, via which material is removed from the container. In this case, the evaluation unit can be configured to control both the first material feed and the second material feed.

[0028] Alternatively, it is possible that the container is without a

[0029] The transport unit is filled or emptied, for example, with constant removal or filling by another mechanism. Accordingly, in this case, the container is emptied or filled via the transport unit. For example, the evaluation unit is then configured to control and / or regulate the material feed of the transport unit for emptying or filling the container.

[0030] According to at least one embodiment or one of the embodiments described above, the evaluation unit is configured to multiply the rate of change by at least one weighting factor to obtain the control value. In other words, by multiplying the rate of change by the weighting factors, the control signal for the material feed is preferably obtained.

[0031] The weighting factor is selected so that a relative change in the material feed rate is no more than 10%. This advantageously reduces very large changes in the material feed rate and protects the hydraulic system of the entire machine.

[0032] According to at least one embodiment or at least one of the embodiments described above, the sensor is arranged in the container such that material is at least temporarily located between the housing and the sensor during filling or emptying of the container. This allows the fill level or the rate of change of the fill level to be determined using the capacitive measuring principle. The housing is, in particular, the container. In this case, the sensor is formed, for example, by the electrically conductive sensor element and the container.

[0033] Furthermore, a dosing system is specified. The dosing system comprises, in particular, a sensor described here. This means that all features disclosed for the sensor are also disclosed for the dosing system, and vice versa.

[0034] According to at least one embodiment, the dosing system comprises a container with a sensor, as described here, and dosing locks for emptying the container. The dosing system further comprises another container, which can in particular be a storage container for the material. Furthermore, the dosing system comprises a transport unit for filling the container with material from the other container.

[0035] According to at least one embodiment of the dosing system or at least one of its above-described embodiments, the transport unit is configured to be operated with a predeterminable material feed rate. In particular, the sensor is configured to specify a control value for the material feed rate. The control value is output, for example, by the sensor's evaluation unit.

[0036] According to at least one embodiment of the dosing system or one of its above-described embodiments, the sensor is configured to reduce the material feed rate in the case of a positive rate of change and to increase the material feed rate in the case of a negative rate of change. The material feed rate is controlled accordingly, for example, using the control value.

[0037] With the dosing system, the material can be brought from the other container into the container and emptied from the container in a controlled manner via dosing locks.

[0038] The dosing system can, for example, be integrated into a construction vehicle or the like for spreading grit. The material is then, for example, grit that is spread via the container and the dosing locks. For example, the grit should be distributed evenly over a surface, such as a road or a defined or prepared surface. It is particularly advantageous if the grit is distributed evenly. For this purpose, the container is preferably filled to a certain fill level. The method described here can ensure that the fill level always remains within a desired range.

[0039] For example, the container serves as an intermediate container between the storage container and the dosing locks and is designed to distribute the material, for example the grit, evenly to the dosing locks.

[0040] The dosing locks are, in particular, lockable. For example, they are rotatable. The evaluation unit can be configured to stop the material feed when the dosing locks are closed.

[0041] The evaluation unit can further be configured to carry out a method comprising the following steps. In step A), a signal value from the sensor is determined. The signal value is, in particular, a raw value or a measured value from the sensor. This means that this value is preferably not offset by a weighting factor or another factor.

[0042] In step B), this signal value is compared with a minimum signal value. This comparison ensures that the fill level within the container has a minimum value. This means that the minimum signal value specifies a lower limit for the fill level. Calibration of the sensor can advantageously be dispensed with, since the minimum signal value can be selected such that a sufficient fill level is present for every conceivable relevant material when the minimum signal value is exceeded.

[0043] In a further step C ) the material feed is increased by 1 % in the case that the initial signal value is smaller than the minimum signal value .

[0044] In particular, steps A) to C) are carried out before determining the rate of change.

[0045] Preferably, steps B) and C) are carried out alternately until the signal value is greater than the minimum signal value.

[0046] Preferably, steps A) to C) are carried out before the container is emptied. Steps A) to C) can ensure, in particular, that a minimal amount of material is present in the container before it is emptied, so that uniform emptying of the container is possible. Subsequent control during emptying of the container is carried out, in particular, by considering the rate of change as described here.

[0047] Further advantages and advantageous embodiments and further developments of the method and the dosing system will become apparent from the following in conjunction with the exemplary embodiments illustrated in the schematic drawings. Identical, similar, and similarly acting elements are provided with the same reference symbols in the figures. The figures and the relative sizes of the elements illustrated in the figures are not generally to scale. Rather, individual elements may be exaggerated for clarity and / or to improve comprehensibility.

[0048] It shows :

[0049] Figure 1 is a schematic illustration of a sensor described here according to a first embodiment.

[0050] Figure 2 is a diagram of a time course of a signal value of a sensor described here;

[0051] Figure 3 is a diagram illustrating a proportionality between the rate of change and the control value;

[0052] Figure 4 is a schematic perspective view of a dosing system described here according to an embodiment; Figure 5 is a schematic block diagram of a method that can be carried out by an evaluation unit of a sensor described here.

[0053] The sensor 10 of Figure 1 has a housing 11 and an electrically conductive sensor element 12. The sensor element 12 is, in particular, an electrically conductive cable. The housing 11 can be a container 2. The sensor 10 is, in particular, arranged in the container 2 in such a way that when the container 2 is filled or emptied, a material 20 passes through the sensor 10. This allows a change in the capacitance of the sensor to be detected. For this purpose, the housing 11 has an inlet opening 17 and an outlet opening 18.

[0054] The sensor 10 further comprises a measuring device 13 and an evaluation unit 14. The measuring unit 13 and the evaluation unit 14 together form, in particular, a control unit 16. For example, a signal and a signal value 15 of the sensor 10 can be determined via the measuring unit 13. For example, the measuring unit 13 is a voltmeter or an ammeter. The evaluation unit 14 is connected to the measuring unit.

[0055] The sensor 10 is a capacitive sensor. During normal operation, a voltage is applied to the sensor, the housing 11 being grounded and the sensor element 12 being brought to a specific electrical potential. The housing 11 forms a first electrode of the capacitive sensor 10 and the sensor element 12 a second electrode of a capacitor. If a fill level changes in a space between the housing 11 and the sensor element 12, i.e. between the first and second electrodes of the sensor 10, the capacitance of the correspondingly formed capacitor changes. Consequently, the voltage applied to the sensor 10 changes. The voltage forms, in particular, the signal from the sensor 10.

[0056] This allows the fill level of the container 2 to be determined based on the measured voltage at the sensor 10, i.e., the signal from the sensor 10. However, a signal value 15 from the sensor 10, which corresponds to a measured voltage value, or the signal from the sensor 10, is material-dependent, since different materials, due to their different dielectric constants, influence the change in the capacitance of the sensor 10 differently. Therefore, calibration of the sensor 10 is necessary to obtain an absolute value for the fill level.

[0057] The sensor 10 described here utilizes the idea of ​​not considering the absolute signal values ​​15 of the sensor 10, but rather determining a rate of change 4 from a change in the voltage of the sensor 10 or the signal of the sensor 10. This allows, for example, the filling or emptying of the container 2 to be controlled so that the container 2 does not overflow or is completely emptied. It is therefore possible to keep the fill level of the container 2 within predeterminable limits using the sensor 10 described here.

[0058] The evaluation unit 14 is configured to determine the rate of change 4 from the sensor signal. Figure 2 shows a diagram illustrating a temporal progression of the signal. A signal value 15, which corresponds to a voltage value of the sensor 10, is plotted against time 51.

[0059] The evaluation unit 14 of the sensor 10 records a plurality of change values ​​lOn. The change values ​​lOn are recorded at time intervals lln. This means that, in the method described here, a temporal change in the signal value 15 in a specific time interval lln is recorded and stored as a change value lOn. Figure 2 illustrates the recording of a change value lOn ​​in a time interval lln.

[0060] The evaluation unit 14 is configured to determine a change rate 4 of the fill level of the container 2 from these change values ​​lOn. For this purpose, the change values ​​lOn are averaged, for example.

[0061] The evaluation unit 14 of the sensor 10 is further configured to output a control value 40, for example for a material feed 100 of a transport unit 6, by means of which the container 2 can be filled or emptied.

[0062] Figure 3 illustrates a relationship between the rate of change 4 and the control value 40. The rate of change 4 is in particular offset against at least one weighting factor 41, 42 in order to obtain the control value 40. The control value 40 is proportional, in particular directly proportional to the rate of change 4. Figure 3 illustrates that a specific value of the rate of change 401 is uniquely assigned to a specific value of the control value 402. The dosing system 1 of Figure 4 has a container 2 and a further container 3. The container 2 can be filled with material 20 from the further container 3 via a transport chain 6, which can be operated with a material feed 100.

[0063] The further container 3 is, in particular, a storage container for the material 20. The material 20 is, for example, grit that can be applied to a surface in a controlled and preferably uniform manner using the dosing system 1.

[0064] The container 2 has rotatable dosing locks 5. The container 2 can be emptied through the rotatable dosing locks 5.

[0065] The container 2 further comprises a sensor 10. The sensor 10 has an electrically conductive sensor element 12, such as a metal cable. The sensor element 12 is preferably electrically insulated from the container 2. The container 2 is a housing 11 for the sensor 10. The sensor 10 is, in particular, a sensor according to the exemplary embodiment of Figure 1.

[0066] The dosing system 1 described here makes use of the idea of ​​not considering the absolute signal values ​​15 of the sensor 10, but rather of determining a rate of change 4 from a change in the voltage of the sensor 10 or the signal of the sensor 10 in order to control the material feed 100.

[0067] Figure 5 illustrates a method for controlling and / or

[0068] Control of a material feed 100 that can be carried out by a sensor 10 described here, in particular an evaluation unit 14 of the sensor 10. The method can be applied, for example, to the dosing system 1 according to Figure 4.

[0069] In the method, a first signal value 15 is determined in a first method step 201. In method step 201, the signal value 15 is compared with a minimum signal value 19. The signal value 15 corresponds to a fill level of the container 2.

[0070] If the signal value 15 is smaller than the minimum signal value 19, the material feed rate 100 is increased in method step 210 in order to increase the signal value 15. For example, in method step 210, the material feed rate 100 is increased relatively by 1% every 100 ms. In this process, the signal value 15 is continuously determined and compared with the minimum signal value 19.

[0071] If the signal value 15 is greater than the minimum signal value 19, a method step 202 determines whether the metering locks 5 are open or closed. If the metering locks are rotatable, step 202 determines whether the metering locks are rigid or rotating.

[0072] If the dosing locks are closed or rigid, the material feed 100 is stopped in step 211. The reason for this is that if the dosing locks are closed or rigid, the container 2 is no longer emptied and further filling of the container 2 with material 20 from the additional container 3 carries the risk of the container 2 overflowing. If the dosing locks 5 are open or rotating, a change rate 4 is determined in method step 203 and it is established whether a new change rate 4 is available. If no new change rate 4 is available, that is to say if the change rate 4 has not changed, for example, compared to a previous run of the method, then no change takes place (method step 212).

[0073] If the rate of change 4 has changed, it is determined in step 204 whether the rate of change 4 is positive or negative. If the rate of change 4 is negative, the rate of change 4 is multiplied by a first weighting factor 41 in step 207 in order to obtain a control value 40 in method step 208 (method step 208).

[0074] If, however, the change rate 4 is positive, the change rate 40 is multiplied by a second weighting factor 42 in method step 205 in order to obtain a control value 40 (method step 208).

[0075] The weighting factors 41 , 42 are selected such that the material feed 100 changes by a maximum of 10 % .

[0076] The control value 40 has a direct correspondence to the material feed 100 . Preferably, the control value 40 is proportional, in particular directly proportional to the rate of change 4 .

[0077] Subsequently, the process can be repeated several times in order to achieve continuous control of the material feed 100.

[0078] The invention described here is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

[0079] Reference symbol list

[0080] 1 dosing system

[0081] 2 containers

[0082] 3 additional containers

[0083] 4 Rate of change

[0084] 5 dosing locks

[0085] 6 transport unit

[0086] 10 Sensor

[0087] 11 housings

[0088] 12 Sensor element

[0089] 13 measuring unit

[0090] 14 Evaluation unit

[0091] 15 Signal value

[0092] 17 Entrance opening

[0093] 18 Exit opening

[0094] 19 minimum signal value

[0095] 20 materials

[0096] 40 Control value

[0097] 41 first weighting factor

[0098] 42 second weighting factor

[0099] 51 Time

[0100] 100 Material feed l On Change value l ln Time interval

[0101] 201...2 12 process steps

[0102] 401 determined value of the rate of change

[0103] 402 specific value of the control value

Claims

Patent claims 1. Capacitive sensor (10) for detecting a change in the fill level of a container (2) filled with a material (20), comprising - an earthed housing (11) as the first electrode, - an electrically conductive sensor element (12) as a second electrode, - a measuring unit (13) - an evaluation unit (14), wherein - the measuring unit (13) is designed to detect a change in the voltage applied to the sensor element (10) as a signal from the sensor (10) when the fill level changes, - the evaluation unit (14) is configured to determine a rate of change (4) of the fill level by means of the signal from the sensor.

2. Sensor (10) according to claim 1, wherein the evaluation unit (14) is designed to - to determine a plurality of change values ​​(lOn) of the signal of the sensor (10) over a plurality of time intervals (lln), and - to determine the rate of change (4) by forming an average value from the plurality of change values ​​(lOn).

3. Sensor (10) according to one of the preceding claims, wherein the evaluation unit (14) is configured to average at least 10 change values ​​(1On) to determine the rate of change (4).

4. Sensor (10) according to one of the preceding claims, wherein - the evaluation unit (14) is designed to output a control value (40) for a material feed (100) for a transport unit (6) via which the container (2) is filled with the material (20) and / or emptied, and - the control value (40) is proportional to the rate of change (4).

5. Sensor (10) according to claim 4, wherein the evaluation unit (14) is configured to multiply the rate of change (4) by at least one weighting factor (41, 42) in order to obtain the control value (40).

6. Sensor (10) according to one of the preceding claims, wherein the sensor (10) is arranged in the container (2) in such a way that material (20) is located at least temporarily between the housing (11) and the sensor element (12) when the container (2) is filled or emptied.

7. Dosing system (1) for a material (20) comprising - a container (2) with a sensor (10) according to one of the preceding claims and metering locks (5) for emptying the container (2), - another container (3) , - a transport unit (6) for filling the container (2) with material (20) from the further container (3).

8. Dosing system (1) according to claim 7, wherein - the transport unit (6) is designed to be operated with a predeterminable material feed (100) become, and - the sensor is configured to specify a control value (40) for the material feed (100).

9. Dosing system according to claim 7 or 8, wherein the sensor (10) is designed to - in case of a positive rate of change (4) to reduce the material feed (100), and - in case of a negative rate of change (4) to increase the material feed (100).

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