MEASURING METHOD AND MEASURING ARRANGEMENT

Description

[0001] The invention relates to a measuring method for determining a measurement result and a measuring arrangement for determining a measurement result.

[0002] In industrial measurement technology, particularly in the field of process automation and process control, measuring devices, such as field devices, are regularly used to record one or more process variables or process parameters. Field devices include, in particular, flow, flow velocity, pressure, differential pressure, temperature, and level measuring devices. Using a corresponding measuring device or measuring arrangement, the field devices typically record a measurement signal that correlates with one or more measured parameters. To determine certain measurement results, it may be necessary to record measured values ​​using multiple measuring devices, for example, to determine a differential pressure.The values ​​measured by the measuring devices are processed by a central location, for example by a PLC computer or another control unit, which must be specifically configured or programmed to evaluate the values ​​measured by the measuring devices.

[0003] A device for measuring pressure is known from US 2004 / 182167 A1. The device comprises a sensor for measuring absolute pressure and a sensor for measuring atmospheric pressure. A relative pressure is determined by calculating a difference between the absolute pressure and the atmospheric pressure. US 2007 / 186623 A1 describes a leak detection system that checks whether a mass content in a liquid container has changed. A signal converter of the leak detection system outputs a differential pressure in the liquid container. The leak detection system can determine the mass content particularly accurately because, in addition to the differential pressure, it also takes into account an ambient pressure measured by a pressure sensor and a temperature measured by a temperature sensor.

[0004] US 2021 / 026001 A1 relates to a radar sensor device for level measurement in a container. When multiple containers are stacked on top of each other, incorrect measurements can occur due to reflections. To correct for such effects, radar waves are emitted not only in the direction of a liquid in the container, but also in the opposite direction. EP 3 605 031 A1 describes a radar sensor for level or limit level measurement. The radar sensor has a sensor unit that can transmit and receive a radar signal through a housing wall.

[0005] The invention is based on the object of providing a measuring method and a measuring arrangement that allow the determination of the density of a filling material in a container without requiring measurements outside the container. This object is achieved by specifying the measuring method according to claim 1 and the measuring arrangement according to claim 9. The subclaims relate to various independent, advantageous developments of the present invention, the features of which can be freely combined with one another by a person skilled in the art within the scope of what is technically reasonable. This applies in particular beyond the boundaries of the various claim categories.

[0006] According to a first aspect of the invention, a measuring method for determining a measurement result is specified, comprising the following steps: measuring a measurand by a first measuring device at a measuring point, wherein the first measuring device determines a first measured value; measuring a reference measurand by a second measuring device, wherein the second measuring device determines a second measured value; data transmission of the second measured value from the second measuring device to the first measuring device; and determining the measurement result by the first measuring device using the first measured value and the second measured value. The measurand is a pressure in a container such as a tank, a pipe, or the like, and the first measuring device has a pressure sensor.According to the invention, the reference measurement variable is a distance between the second measuring device and a fill level of a filling material in the container, and the measurement result is a density of the filling material. The second measuring device comprises a distance sensor. The density of the filling material can be calculated based on the fill level and the hydrostatic pressure prevailing in the container, optionally using additional auxiliary variables. According to the invention, it is possible for the distance sensor to be a radar sensor, but it can also be a distance sensor of another type.

[0007] The measuring devices can have sensors of any type. The measuring devices can also have communication means, for example, network adapters for communication via wired and / or wireless networks. Data transmission between the first measuring device and the second measuring device can thus take place, for example, via a wired or wireless network, or even via a direct connection.

[0008] According to the invention, the method can be configured such that at least one additional measuring device measures the reference measurement variable, wherein the at least one additional measuring device determines an additional measurement value, wherein data of the additional measurement value is transmitted from the additional measuring device to the first measuring device, and wherein the first measuring device compares the second measurement value with the additional measurement value before determining the measurement result in order to reject and / or correct the second measurement value. Thus, the reference measurement variable is measured by different devices. Measurement errors can be corrected. Furthermore, in the event of a failure of the second measuring device, another option for obtaining the reference measurement variable is provided by the first measuring device.If the first measuring device rejects the second measured value, then according to the invention it can instead use the additional measured value to determine the measurement result, or it can wait to receive another measured value from the second measuring device.

[0009] If multiple additional measuring devices are present, the first measuring device receives multiple additional measured values. According to the invention, the method can be designed such that the first measuring device carries out a voting process. The method thus utilizes redundancies. Thus, according to the invention, a voting process can be carried out according to the 1oo2 principle, according to the 2oo2 principle, according to the 2oo3 principle, or according to related voting processes. It is particularly advantageous if the first measuring device selects a suitable voting process depending on the number of additional measuring devices present or the number of additional measured values ​​provided by them. According to one example, if only one additional measuring device is present, voting could be carried out according to the 2oo2 principle, and when a further additional measuring device is connected, the first measuring device could automatically switch to voting according to the 2oo3 principle.In addition to the voting methods mentioned, the person skilled in the art can also use other methods for error correction that are conceivable when obtaining measured values ​​from different measuring points, for example calculating an average from the measured values ​​obtained.

[0010] According to a further variant of the method according to the invention, an additional measuring device measures the reference measured variable, wherein the at least one additional measuring device determines an additional measured value, wherein data of the additional measured value is transmitted from the additional measuring device to the second measuring device, and wherein the second measuring device compares the second measured value with the additional measured value and outputs an error signal if a difference between the second measured value and the additional measured value exceeds a limit value. In this way, the second measuring device can check whether its measurements are still correct. If the values ​​measured by the second measuring device and the additional measuring device deviate too greatly from one another, it is possible that at least one of the two measuring devices is defective or needs to be recalibrated.According to the described variant of the procedure, a large number of measuring devices can send each other measured values ​​regarding the reference measured quantity and thus check whether they are still functioning correctly.

[0011] Preferably, the first measuring device measures the reference measured variable in addition to the measured variable, wherein the first measuring device determines a third measured value, and wherein data of the third measured value is transmitted from the first measuring device to at least one third measuring device. If the first measuring device has a suitable sensor for this purpose, then it is possible for the first measuring device to also measure the reference measured variable. In a system with multiple measuring devices, a separate measuring device designed exclusively for measuring atmospheric pressure is therefore not necessary—the required measured values ​​are determined by the first measuring device.

[0012] It is advantageous if the first measuring device sends a request, whereupon the second measuring device receives the request and measures the reference measured variable in order to determine the second measured value. According to the invention, the request can be received, for example, via a network or via any other data connection, which according to the invention can also be implemented wirelessly. The measurement of the reference measured variable is thus triggered by a query within the framework of a polling process. However, embodiments of the method according to the invention are also possible in which the second measuring device itself triggers the measurement of the reference measured variable. For example, the reference measured variable can be measured by the second measuring device at regular time intervals.

[0013] Preferably, the request contains a time at which the reference measurand is to be measured, wherein the second measuring device measures the reference measurand at that time or as close as possible to that time. For this purpose, the second measuring device can be equipped with a clock, which the second measuring device can preferably synchronize with an external time source, e.g., via a network connection. Measuring the reference measurand at a specific time is particularly important when a differential pressure is to be measured. Thus, the first measuring device can specify when the second measuring device is to measure the reference measurand. The first measuring device preferably also measures the measurand at that time.

[0014] The first measuring device preferably generates a first time stamp upon determining the first measured value, wherein the second measuring device generates a second time stamp upon determining the second measured value, wherein data of the second time stamp is transmitted from the second measuring device to the first measuring device, and wherein the first measuring device determines the measurement result using the first measured value and the second measured value only if a time difference between the first time stamp and the second time stamp does not exceed a maximum time interval. The first measuring device can thus measure the measured value and wait for receipt of a permissible measured value suitable for determining the measurement result.It is not necessarily necessary for the first measuring device to actively query the reference measured value from the second measuring device as described above, but it can also simply wait for the receipt of a permissible second measured value from the second measuring device.

[0015] It is advantageous if the method according to the invention is designed such that the second measuring device adds an identifier to the second measured value, and the first measuring device recognizes the second measured value as a permissible measured value based on the identifier. Thus, any number of second measuring devices can be added to a measuring arrangement. When the first measuring device receives a second measured value and recognizes its identifier, it can process the second measured value immediately according to the method. A complex reconfiguration of the system when adding a new measuring device is therefore not necessary.

[0016] According to a further aspect of the invention, a measuring arrangement for determining a measurement result is proposed, comprising: a first measuring device for measuring a measurand at a measuring point, wherein the first measuring device is configured to determine a first measured value when measuring the measurand and to determine the measurement result using the first measured value and a second measured value, and a second measuring device for measuring a reference measurand, wherein the second measuring device is configured to determine the second measured value when measuring the reference measurand and to initiate data transmission of the second measured value from the second measuring device to the first measuring device so that the first measuring device can determine the measurement result. The measurand is a pressure in a container such as a tank, a pipe or the like, and the first measuring device has a pressure sensor.According to the invention, the reference measurement variable is a distance between the second measuring device and a fill level of a filling material in the container, and the measurement result is a density of the filling material, wherein the second measuring device comprises a distance sensor. This measuring arrangement is preferably designed such that it can also carry out the method described above according to its various optional variants. If the second measuring device initiates the data transmission of the second measured value to the first measuring device, this does not necessarily mean a directed data transmission in which only the first measuring device is the addressee. The second measured value can, for example, also be sent in a broadcast packet.

[0017] The measuring arrangement preferably has at least one additional measuring device, wherein the at least one additional measuring device is configured to measure the reference measured variable and in the process to determine an additional measured value, wherein the at least one additional measuring device is configured to send the additional measured value, wherein the first measuring device is configured to receive the additional measured value, and wherein the first measuring device is configured to compare the second measured value with the additional measured value before determining the measurement result in order to reject and / or correct the second measured value.It is further possible according to the invention that the additional measuring device is configured to measure the reference measured variable, to determine at least one additional measured value and to send the additional measured value, wherein the second measuring device is configured to receive the additional measured value, and wherein the second measuring device is configured to compare the second measured value with the additional measured value and to output an error signal if a difference between the second measured value and the additional measured value exceeds a limit value.

[0018] According to an advantageous variant of the measuring arrangement according to the invention, the first measuring device is configured to measure the reference measured value in addition to the measured value and thereby determine a third measured value. The first measuring device is configured to transmit the third measured value, and the measuring arrangement further comprises at least one third measuring device configured to receive the third measured value. In this variant of the measuring arrangement, the first measuring device must have a sensor for measuring the reference measured value.

[0019] Preferably, the first measuring device is configured to send a request, and the second measuring device is configured to receive the request and then measure the reference measurement variable to determine the second measurement value. According to the invention, the request may contain a time at which the reference measurement variable is to be measured, with the second measuring device being configured to measure the reference measurement variable at that time or as close as possible to that time.

[0020] Preferably, the first measuring device is configured to generate a first time stamp upon determining the first measured value, the second measuring device is configured to generate a second time stamp upon determining the second measured value, the second measuring device is configured to send the second time stamp, the first measuring device is configured to receive the second time stamp, and the first measuring device is configured to determine the measurement result using the first measured value and the second measured value only if a time difference between the first time stamp and the second time stamp does not exceed a maximum time interval. Particularly preferably, the second measuring device is configured to add an identifier to the second measured value, and the first measuring device is configured to recognize the second measured value as a permissible measured value based on the identifier.

[0021] It is understood that the measuring arrangement may comprise additional devices useful for carrying out the method described above. Thus, according to the invention, the measuring arrangement may comprise communication lines. These may connect the measuring devices directly or indirectly. The measuring arrangement may further comprise a control unit. This may query and transmit data from the measuring devices and serve as a communication hub connected between the measuring devices.

[0022] The drawings are for illustrative purposes only. They show: Fig. 1 a schematic representation of a first measuring arrangement not belonging to the invention for measuring a relative pressure, Fig. 2 a schematic representation of a second measuring arrangement not belonging to the invention for measuring a differential pressure, Fig. 3a schematic representation of a third measuring arrangement according to the invention for measuring a density and Fig. 4 a flow chart illustrating method steps according to the invention.

[0023] Fig. 1shows a schematic representation of a first measuring arrangement 1 for measuring a relative pressure, which does not belong to the invention. Several containers 2 are shown. In each container 2, a first measuring device 3 is arranged. The first measuring device 3 has a sensor for measuring an absolute pressure. Each of the first measuring devices 3 is connected to a control unit 5 via a communication line 4. A second measuring device 6 is connected to the control unit 5 via a further communication line 4. The second measuring device 6 also has a sensor for measuring an absolute pressure. According to the measuring arrangement 1 shown, the second measuring device 6 is arranged outdoors so that it can measure an atmospheric pressure. The first measuring device 3 measures an absolute pressure of a liquid in the container 2, determining a first measured value. The second measuring device 6 measures the atmospheric pressure and thereby determines a second measured value.The second measuring device 6 transmits the second measured value to the first measuring device 3 via the control unit 5 and the communication lines 4. The first measuring device 3 subtracts the second measured value from the first measured value and thus obtains a relative pressure of the liquid in the container 2. From the relative pressure, the first measuring device derives a fill level of the liquid in the container.

[0024] The measuring arrangement further comprises two additional measuring devices 7. The additional measuring devices 7 have sensors for measuring absolute pressure and, like the second measuring device 6, are arranged so that they can measure atmospheric pressure. The additional measuring devices 7 each determine an additional measured value. The two additional measured values ​​are transmitted to the first measuring device 3 via the communication lines 4 and the control unit 5. The first measuring device 3 uses the additional measured values ​​to check whether the second measured value, which the first measuring device 3 received from the second measuring device 6, is correct. The first measuring device 3 performs a 2oo3 voting for this purpose. To do this, it takes into account the second measured value and the two additional measured values. For example, the second measured value can be discarded if it deviates too significantly from the two additional measured values.According to another operating mode of the first measuring device 3, the first measuring device 3 calculates an average value from the second measured value and the two additional measured values, thus correcting the second measured value. The additional measuring devices 7 also transmit the additional measured values ​​to the second measuring device 6. Furthermore, the second measuring device 6 transmits the second measured value it has determined to the additional measuring devices 7. The measuring devices compare received measured values ​​with self-determined measured values. In this way, the second measuring device 6 and the additional measuring devices 7 can check whether they are still determining permissible measured values. If the measured values ​​differ too greatly from one another, this may indicate a malfunction.

[0025] Fig. 2shows a schematic representation of a second measuring arrangement 1 for measuring a differential pressure, which is not part of the invention. The measuring arrangement 1 has several measuring devices of similar construction. One of the measuring devices is a first measuring device 3, which is intended to determine a differential pressure. It sends a request to a second measuring device via a network formed by a control unit 5 and a plurality of measuring devices connected to it. The request specifies a time at which the second measuring device is to measure a pressure. The first measuring device 3 measures an absolute pressure at that time, determining a first measured value.

[0026] The second measuring device 6 also measures an absolute pressure at that time, thereby determining a second measured value. The second measuring device 6 transmits the second measured value via the network to the first measuring device 3. The first measuring device 3 calculates the difference between the first measured value and the second measured value, thus determining the differential pressure.

[0027] Fig. 3shows a schematic representation of a third measuring arrangement 1 for measuring a density according to the present invention. A container 2 contains a liquid 8 whose density is to be determined. A first measuring device 3 having a pressure sensor is arranged in the container. The measuring device 3 is connected to a second measuring device 6 via a communication line 4. The first measuring device 3 measures a pressure of the liquid 8, determining a first measured value. The second measuring device 6 is a radar distance sensor. It measures a distance between the second measuring device 6 and a surface of the liquid 8, determining a second measured value. The second measuring device 6 transmits the second measured value to the first measuring device 3 via the communication line 4. The first measuring device 3 then determines a density of the liquid 8 based on the first measured value and the second measured value.

[0028] Fig. 4shows a flowchart illustrating method steps according to the invention. In a first measuring step 9, a first measuring device measures a measured variable. The measurement of the measured variable results in a first measured value. In a second measuring step 10, a second measuring device measures a reference measured variable. The measurement of the reference measured variable results in a second measured value. It should be noted that the first measuring step 9 and the second measuring step 10 do not necessarily have to be carried out in the order shown, but their order can also be swapped, or the two steps can be carried out simultaneously.

[0029] In a transmission step 11, data of the second measured value is transmitted from the second measuring device to the first measuring device. This can be done, for example, via a wired network or via a wireless data connection. It should be noted that the transmission step 11 does not necessarily have to be carried out after the first measuring step 9, because it is also possible for the first measuring device to determine the first measured value only after it has received the second measured value. After determining the first measured value and receiving the second measured value, the first measuring device determines a measurement result from the first measured value and the second measured value in a determination step 12. The measurement result is a density of a liquid, corresponding to the Fig. 3 presented embodiment of the invention. List of reference symbols

[0030] 1Measuring arrangement 2Container 3First measuring device 4Communication line 5Control unit 6Second measuring device 7Additional measuring device 8Liquid 9First measuring step 10Second measuring step 11Transmission step 12Determination step

Claims

1. A measuring method for determining a measurement result, comprising the steps of: - measuring a measuring quantity by means of a first measuring device (3) at a measuring point, wherein the first measuring device (3) detects a first measurement value, - measuring a reference measuring quantity by means of a second measuring device (6), wherein the second measuring device (6) detects a second measurement value, - data transmission of the second measurement value from the second measuring device (6) to the first measuring device (3), and - determination of the measurement result by the first measuring device (3) using the first measurement value and the second measurement value, wherein, the measuring quantity is a pressure in a container (2), such as a tank, a pipe or the like and wherein the first measuring device (3) has a pressure sensor characterized in that the reference measuring quantity is a distance between the second measuring device (6) and a filling level of a filling material in the container (2), and that the measurement result is a density of the filling material, wherein the second measuring device (6) has a distance sensor.

2. The measuring method according to claim 1, characterized in that at least one additional measuring device (7) measures the reference measuring quantity, wherein the at least one additional measuring device (7) detects an additional measurement value, wherein a data transmission of the additional measurement value from the additional measuring device (7) to the first measuring device (3) takes place, and wherein the first measuring device (3) compares the second measurement value with the additional measurement value prior to the determination of the measurement result in order to discard and / or correct the second measurement value.

3. The measuring method according to claim 1, characterized in that at least one additional measuring device (7) measures the reference measuring quantity, wherein the at least one additional measuring device (7) detects an additional measurement value, wherein a data transmission of the additional measurement value from the additional measuring device (7) to the second measuring device (6) takes place, and wherein the second measuring device (6) compares the second measurement value with the additional measurement value and outputs an error signal if a difference between the second measurement value and the additional measurement value exceeds a threshold value.

4. The measuring method according to any one of the preceding claims, characterized in that the first measuring device (3), in addition to the measuring quantity, measures the reference measuring quantity, wherein the first measuring device (3) detects a third measurement value, and wherein a data transmission of the third measurement value from the first measuring device (3) to at least one third measuring device takes place.

5. The measuring method according to any one of the preceding claims, characterized in that the first measuring device (3) sends a request, whereupon the second measuring device (6) receives the request and measures the reference measuring quantity in order to detect the second measurement value.

6. The measuring method according to claim 5, characterized in that the request contains a point in time at which the reference measuring quantity is to be measured, wherein the second measuring device (6) measures the reference measuring quantity at the point in time or as closely as possible to the point in time.

7. The measuring method according to any one of the preceding claims, characterized in that the first measuring device (3) generates a first time stamp during the detection of the first measurement value, wherein the second measuring device (6) generates a second time stamp during the detection of the second measurement value, wherein a data transmission of the second time stamp from the second measuring device (6) to the first measuring device (3) takes place, and wherein the first measuring device (3) carries out the determination of the measurement result, using the first measurement value and the second measurement value, only if a difference in time between the first time stamp and the second time stamp does not exceed a maximum time interval.

8. The measuring method according to any one of the preceding claims, characterized in that the second measuring device adds an identifier to the second measurement value, and that the first measuring device recognizes the second measurement value as an admissible measurement value based on the identifier.

9. A measuring assembly (1) for determining a measurement result, comprising: - a first measuring device (3) for measuring a measuring quantity at a measuring point, wherein the first measuring device (3) is configured for detecting a first measurement value during the measurement of the measuring quantity and for determining the measurement result using the first measurement value and a second measurement value, and - a second measuring device (6) for measuring a reference measuring quantity, wherein the second measuring device (6) is configured for detecting the second measurement value during the measurement of the reference measuring quantity and for causing a data transmission of the second measurement value from the second measuring device (6) to the first measuring device (3), so that the first measuring device (3) can determine the measurement result wherein, the measuring quantity is a pressure in a container (2), such as a tank, a pipe or the like and wherein the first measuring device (3) has a pressure sensor characterized in that the reference measuring quantity is a distance between the second measuring device (6) and a filling level of a filling material in the container (2), and that the measurement result is a density of the filling material, wherein the second measuring device (6) has a distance sensor.