Fill level measuring system and method

Abstract

The invention relates to a fill level measuring system (1) for measuring the fill level in a reservoir, comprising a sensor element (8) which is arranged relative to a surface (2) of a substance in the reservoir and designed to transmit a measuring signal in the direction of the surface (2) and to receive a reflection signal reflected from the surface (2) in response to the measuring signal, and comprising a processing unit (14) which is designed such that, based on the time difference between the transmitting of the measuring signal and the receiving of the reflection signal, it carries out a travel time measurement and processes measurement values of the travel time measurement, in order to determine a fill level of the reservoir, wherein the processing unit (14) is designed to detect disturbances on the surface (2) and to take this into account when determining the fill level.

Description

[0001] Description

[0002] Level measurement system and method

[0003] The present invention relates to a level measuring system for measuring the level in a reservoir according to the preamble of patent claim 1. Furthermore, the present invention relates to a method for measuring the level in a reservoir according to the preamble of patent claim 9.

[0004] Reservoirs can be used to store a fluid or other substance and are usually connected to pipes to transfer the contents of the reservoir to other devices or equipment. For example, the reservoir could be a lubricant reservoir for storing oil or grease, with the lubricant being delivered to lubrication systems for bearings or similar. In this case, it is often necessary to monitor the reservoir level. The reservoir level can be monitored by various monitoring devices, such as a float sensor or capacitive sensors. As long as there is no movement of the reservoir contents that leads to surface movement, float sensors, for example, offer a cost-effective and accurate determination of the level.

[0005] However, as soon as the surface of the substance stored in the reservoir is subjected to disturbances, such as when the reservoir's contents are stirred by impellers or set in motion by vibrations and / or movements of the reservoir, accurate information can no longer be obtained using a conventional float sensor. Such a float sensor would move with the surface, which forms hills and valleys due to the movement, and would therefore lead to higher or lower fill levels than the actual fill level. The use of other known sensors, such as acoustic sensors, would also lead to inaccurate fill level information in the event of such disturbances.

[0006] It is therefore an object of the present invention to provide a system and method for determining the fill level in a reservoir, which enables an accurate measurement of the fill level even if the surface of the contents of the reservoir is irregular.

[0007] This object is achieved by a level measuring system for measuring the level in a reservoir according to patent claim 1 and a method for measuring the level in a reservoir according to patent claim 9.

[0008] The level measuring system for measuring the level in a reservoir has a sensor element that is arranged relative to a surface of a substance present in the reservoir and is configured to transmit a measurement signal towards the surface and to receive a reflection signal reflected from the surface in response to the measurement signal. The sensor element can be any type of optical sensor element, such as an ultrasonic sensor, infrared sensor, or similar. In any case, the sensor element is suitable for transmitting a signal towards the surface, which is reflected from the surface. The reflection signal is then received again by the sensor element, and the time interval between the transmission and reception of the signal is subsequently used by a processing unit of the level measuring system to perform a transit time measurement based on this time difference.The processing unit is further configured to process the measured values ​​from the transit time measurement to determine the reservoir's fill level. The longer the transit time, the lower the reservoir's fill level.

[0009] In order to be able to determine the fill level independently of surface irregularities, such as those that can arise from stirring the reservoir contents, compared to previous systems, the processing unit is configured to detect such surface disturbances and take them into account when determining the fill level. This allows the data obtained from the time-of-flight measurement to be corrected accordingly when disturbances are detected, thus improving the determination of the reservoir's fill level.

[0010] According to one embodiment, the processing unit is configured to perform a moving average calculation of the measured values ​​of the runtime measurement. During the moving average calculation, a new average is continuously calculated based on new measured values ​​of the runtime measurement. This can be done, for example, according to the following formula:

[0011] GMWnew = GMWait minus GMWait / D + NW / D where GMW is the moving average, NW is the new value, i.e., the current value of the runtime measurement, and D is the number of values ​​used for the moving average. D should be at least greater than or equal to 1. The larger D is selected, the slower the moving average changes, thus increasing the damping of the calculation. Higher damping means that changes in the fill level become noticeable more slowly. The current moving average of the measured values ​​can be defined as the current fill level.

[0012] If the contents of a reservoir are gradually released or filled, or if the reservoir or its contents are moved, the surface of the substance in the reservoir, and thus the fill level, are subject to continuous changes and disturbances, which is why the measured values ​​of the runtime measurement do not always correspond to the fill level. For example, in a grease reservoir with agitator blades, the grease surface often forms hills and valleys that shift and change during operation. Wave-like surface movements can also occur in reservoirs of oil circulating units. The fill level measuring system described here can detect such surface movements and take them into account when determining the fill level.

[0013] According to a further embodiment, the processing unit is configured to compare a current measured value with the moving average and, if the current measured value deviates from the moving average by more than a predefined threshold, to classify the current measured value as erroneous. This means that the processing unit can analyze current measured values ​​and classify them as disturbances or outliers. If current measured values ​​are identified as disturbances, they are subsequently no longer considered in the moving average calculation in order to maintain high measurement accuracy.Since the current measured values ​​are compared to a threshold value, minor deviations that would not distort the moving average can be ignored. Only large deviations that would disproportionately distort the overall result of the level determination are specified as disturbances and ignored during the moving average calculation. The threshold value can be selected depending on the actual application, for example, depending on the reservoir content.

[0014] Particularly when using a stirrer in the reservoir, surface movements can occur cyclically. Therefore, according to a further embodiment, the processing unit can be configured to determine whether the measured value classified as erroneous occurs cyclically. Such a cyclical occurrence of the measured value classified as erroneous is then defined by the processing unit as a cyclic disturbance and is not included in the averaging. Such cyclic disturbances indicate, for example, that the disturbance is caused by the stirring blades of a unit and is not related to the actual fill level.

[0015] According to a further embodiment, the processing unit is configured to issue a warning signal when the determined fill level of the reservoir falls below a predefined lower limit. For example, a pre-warning can be issued at a fill level of 20%, and a warning can be issued at a fill level of 10% to prompt refilling of the reservoir. Other limits and other types of warning signals are also possible.

[0016] As explained above, the substance in the reservoir can be a lubricating grease. Other types of substances, such as fluids or solids, such as granules, that can be stored in a reservoir are also possible.

[0017] According to a further aspect, a method for measuring the fill level in a reservoir is proposed, the method comprising the steps of: transmitting a measurement signal toward a surface of a substance present in the reservoir, receiving a reflection signal reflected from the surface in response to the measurement signal, performing a time-of-flight measurement based on the time difference between transmitting the measurement signal and receiving the reflection signal, and processing measured values ​​of the time-of-flight measurement to determine a fill level of the reservoir. The method further comprises: detecting disturbances on the surface and taking the disturbances into account when determining the fill level.

[0018] The advantages and embodiments described above with respect to the level measuring system apply accordingly to the method for measuring the level in a reservoir and vice versa.

[0019] Furthermore, a computer program product is proposed which has a program code which is designed to cause the method as explained above to be carried out on a computer.

[0020] A computer program product, such as a computer program means, can be provided or delivered, for example, as a storage medium, such as a memory card, USB stick, CD-ROM, DVD, or in the form of a downloadable file from a server in a network. This can be done, for example, in a wireless communications network by transmitting a corresponding file with the computer program product or the computer program means.

[0021] Further advantages and advantageous embodiments are set forth in the description, the drawings, and the claims. In particular, the combinations of features set forth in the description and the drawings are purely exemplary, so the features may also be present individually or in other combinations.

[0022] The invention will be described in more detail below with reference to exemplary embodiments illustrated in the drawings. The exemplary embodiments and the combinations shown in the exemplary embodiments are purely exemplary and are not intended to define the scope of the invention. This scope is defined solely by the appended claims. It shows:

[0023] Fig. 1 : a schematic sectional view of a level measuring system.

[0024] In the following, identical or functionally equivalent elements are identified by the same reference symbols.

[0025] Fig. 1 shows a level measuring system 1 designed to measure the level of a substance in a reservoir. The level measuring system 1 comprises a sensor housing 4 with a base plate 6, wherein the base plate 6 can be connected to the sensor housing 4 via fastening means 28. The sensor housing 4, with its base plate 6, defines an interior space 10 in which a sensor element 8 and evaluation electronics 12 with a processing unit 14 are arranged. Furthermore, the sensor housing 4 comprises a connection 16 via which the level measuring system can be connected to external devices, such as computing devices, etc. The level measuring system can be connected to the reservoir (not shown) via fastening means 18.

[0026] In order to measure the fill level 2, the sensor element 8 is configured to emit a signal that is reflected by a surface 2 of the reservoir's contents and then received again by the sensor element 8. The sensor element 8 can be designed to transmit and / or receive the signal within a measuring lobe 20. The processing unit 14 can then perform a time-of-flight measurement using the transmitted and reflected signal in order to determine a distance 22 between the sensor element 8 and the surface 2. The fill level of the reservoir can be determined, for example, by calculating a moving average of the measured values ​​of the time-of-flight measurement. The moving average reflects the fill level.

[0027] In a reservoir in which, for example, lubricating grease is stored, agitator blades can be provided to stir the contents of the reservoir. Such processes, or other processes in the reservoir, for example movement of the reservoir in the case of a vehicle tank, can lead to surface disturbances. Such surface disturbances lead to movements of the surface 2 and thus to fluctuating measured values ​​by the sensor element 8. In order to detect such disturbances, which can falsify the determination of the fill level, and to exclude them from the determination of the fill level, the processing unit 14 is configured to detect these disturbances and to disregard them when calculating the mean value. For example, the processing unit 14 can classify a measured value as erroneous if it deviates from the moving average by a predefined threshold value.Such fluctuations in the measured values ​​can be interpreted as disturbances and the processing unit 14 then ignores them when calculating the mean value.

[0028] Additionally, the processing unit 14 can detect whether these are cyclic disturbances. Cyclical disturbances are often caused by agitators or similar devices in the reservoir and can therefore be interpreted as disturbances unrelated to the fill level.

[0029] The level measurement system proposed here makes it possible to easily determine the level of a reservoir, whereby movements of the reservoir contents that could lead to incorrect level determinations are detected and taken into account accordingly.

[0030] List of reference symbols

[0031] 1 level measuring system

[0032] 2 Surface

[0033] 4 sensor housings

[0034] 6 Base plate

[0035] 8 Sensor element

[0036] 10 interior element

[0037] 12 Evaluation electronics

[0038] 14 Processing unit

[0039] 16 connection

[0040] 18 fasteners

[0041] 20 measuring lobe

[0042] 22 Distance

Claims

P a t e n t a n s p r ü c h e Level measuring system and method Level measuring system (1) for measuring the level in a reservoir, comprising a sensor element (8) arranged relative to a surface (2) of a substance present in the reservoir and configured to send a measurement signal towards the surface (2) and to receive a reflection signal reflected from the surface (2) in response to the measurement signal, and comprising a processing unit (14) configured to perform a time-of-flight measurement based on the time difference between sending the measurement signal and receiving the reflection signal and to process measured values ​​of the time-of-flight measurement in order to determine a level of the reservoir, characterized in that the processing unit (14) is configured to detect disturbances on the surface (2) and to take them into account when determining the level.Level measuring system according to claim 1, wherein the processing unit (14) is configured to subject the measured values ​​to a moving average calculation. Level measuring system according to claim 2, wherein the current moving average of the measured values ​​is the current level. Level measuring system according to claim 2 or 3, wherein the processing unit (14) is configured to compare a current measured value with the moving average, and if the current measured value deviates by more than a predefined amount, A level measuring system according to claim 4, wherein the processing unit (14) is configured to determine whether the erroneously classified measured value occurs cyclically. A level measuring system according to claim 5, wherein, if it is determined that the erroneously classified measured value occurs cyclically, the processing unit (14) is configured to define the erroneous mean value as a cyclic disturbance and not include it in the averaging. A level measuring system according to any one of the preceding claims, wherein the processing unit (14) is configured to output a warning signal when the determined level of the reservoir falls below a predefined lower limit. A level measuring system according to any one of the preceding claims, wherein the substance in the reservoir is a lubricating grease.A method for measuring the fill level in a reservoir, comprising the steps of: sending a measurement signal towards a surface (2) of a substance present in the reservoir, receiving a reflection signal reflected from the surface (2) in response to the measurement signal, performing a time-of-flight measurement based on the time difference between sending the measurement signal and receiving the reflection signal, and processing measured values ​​of the time-of-flight measurement to determine a fill level of the reservoir, characterized in that the method further comprises: detecting disturbances on the surface (2) and taking the disturbances into account when determining the fill level.

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