Method for operating a Coriolis measuring device

Abstract

The invention relates to a method (100) for operating a Coriolis measuring device (1), wherein the method comprises the following steps: recording a measurement voltage of a sensor for sensing vibrations of a measuring tube and, for the purpose of diagnosing the Coriolis measuring device (101), creating an asymmetry value sequence (AS) from the amplitude of this measurement voltage; recording at least one stable variable and creating a stable asymmetry value sequence (SAS) based on the stable variable (102), wherein the stable variable is one of the following variables or a first-order or further time derivative thereof: a resonant frequency of the measuring tube containing the medium or a variable derived therefrom, a time or phase difference between measurement signals from a first sensor and a second sensor or a variable derived therefrom, a measuring tube wall temperature, a temperature difference between two measuring points of the measuring tube wall.

Description

Technical Field

[0001] The invention relates to a method for operating a Coriolis measuring device for measuring the density and / or the mass flow of a medium flowing through a pipeline. Background Art

[0002] In a Coriolis measuring device, at least one measuring tube is excited to vibrate; see, for example, DE 10 2016 12 55 37 A1. The medium flowing through the measuring tube distorts the characteristics of these vibrations. These vibrations are typically detected by two sensors and evaluated by an electronic measuring / operating circuit. Due to manufacturing inaccuracies, the sensors often have slightly asymmetric measurements, meaning that a low flow rate is measured when the flow rate is zero. This asymmetry can be corrected after the initial calibration of the measuring device. This calibration deviation represents a separate measured variable. However, this measured variable can be very noisy. Summary of the Invention

[0003] It is therefore an object of the present invention to provide a method by which the measured value of a measured variable which is dependent on deviations of sensor asymmetry from an initial state is stabilized.

[0004] This object is achieved by a method according to independent claim 1 .

[0005] In a method according to the invention for operating a Coriolis measuring device for measuring the density and / or mass flow of a medium flowing through a pipeline,

[0006] The Coriolis measuring device comprises at least one measuring tube for conducting a medium, each measuring tube having an inlet and an outlet and a measuring tube wall surrounding a measuring tube lumen;

[0007] at least one exciter for generating vibrations of the measuring tube, and a first sensor on the inlet side and a second sensor on the outlet side for sensing the vibrations of the measuring tube, wherein the exciter and the sensor each comprise a coil arrangement with at least one coil and a magnetic arrangement with at least one magnet,

[0008] wherein the coil device and the magnetic device of each sensor are moved relative to one another by vibration of the measuring tube, during which an electrical measuring voltage is induced in the coil;

[0009] electronic measuring / operating circuitry for operating the actuator, for sensing and evaluating the electrical measuring voltage, and for outputting measured values of the density and / or mass flow and diagnostic information,

[0010] The method comprises the following steps:

[0011] In a first method step, a measured voltage from the sensor is recorded and a sequence of asymmetry values is created from the amplitude of the measured voltage in order to diagnose the Coriolis measuring device.

[0012] In a second method step, a measurement signal of at least one stable variable is recorded,

[0013] In a third method step, a stable asymmetric value sequence is created based on the asymmetric value sequence according to the stable variable,

[0014] where the stable variable is based on one of the following variables or its first or second time derivative:

[0015] the resonant frequency of the measuring tube containing the medium or a variable derived therefrom,

[0016] a time or phase difference between the measurement signals from the first sensor and the second sensor, or a variable derived therefrom,

[0017] Measure the temperature of the pipe wall,

[0018] Measure the temperature difference between two measuring points on the pipe wall.

[0019] The first method step and the second method step can also be carried out in reverse order or simultaneously.

[0020] To create the sequence of asymmetry values, the ratio of the absolute deviations of the measured voltage amplitudes to the average value of the measured voltage amplitudes can be formed.

[0021] In particular, the time average of the absolute value of the first or second time derivative of the variable of the stationary variable may be used.

[0022] In one embodiment, a spread of the measured values of the stabilizing variable is determined, wherein the asymmetry measure is stabilized by the spread.

[0023] In one embodiment, when the spread value exceeds a first limit value, the last valid value of the asymmetry value sequence is used as the current value of the asymmetry value sequence, or the asymmetry value sequence is set to a predetermined value.

[0024] For example, the predetermined value may be zero or NaN (Not a Number) or other values that indicate that the sequence of asymmetry values is invalid at certain times or within certain time ranges. Thus, for example, the electronic measurement / operation circuitry may identify whether the values of the sequence of asymmetry values correspond to measured values of asymmetry or whether to ignore these values when determining the state of the Coriolis measurement device.

[0025] In particular in the case of media containing a plurality of media components, possibly in different material states, the asymmetry value sequence can temporarily deviate greatly from the mean value and thus be distorted in a destructive manner, so that replacing the asymmetry value sequence through the last valid value or through the predetermined value provides a significantly more stable asymmetry value sequence.

[0026] In one embodiment, an average value is formed of the measured values of the stable variable, wherein the first limit value is derived from the distribution value and / or the average value, or wherein the first limit value is a configured or configurable or predetermined value. For example, the first limit value can be determined by a relative or absolute deviation from the normal distribution in a single-phase medium or a pure medium.

[0027] In one embodiment, the average value is a moving average value having a first time window, and wherein the dispersion value is a moving dispersion value having a second time window.

[0028] In this way, the calculation of the mean value and the spread value can be adapted to the measurement situation or the measurement point, so that the asymmetry value sequence is stabilized.

[0029] In one embodiment, the first time window has a duration of at least 0.2 seconds and in particular at least 0.5 seconds and preferably at least 1 second, and / or the first time window has a duration of at most 90 seconds and in particular at most 70 seconds and preferably at most 60 seconds.

[0030] In one embodiment, the second time window has a duration of at least 2 seconds and in particular at least 4 seconds and preferably at least 5 seconds, and / or wherein the second time window has a duration of at most 150 seconds and in particular at most 130 seconds and preferably at most 120 seconds.

[0031] In one embodiment, if the time or phase difference or a variable derived therefrom is below a second limit value and the asymmetry exceeds a third limit value, then

[0032] The last valid measured value of the asymmetry value sequence is used as the current value of the asymmetry value sequence,

[0033] Alternatively, the asymmetry value sequence is set to a predetermined value.

[0034] In this way, partial filling of the measuring tube caused by asymmetry when the medium is stationary can be detected and ruled out. For example, the second limit value can correspond to a value of less than 5%, in particular less than 1%, preferably less than 0.1% of the maximum specified mass flow rate. For example, the third limit value can be an asymmetry of at least 0.1%, in particular at least 1%, preferably at least 5%.

[0035] In one embodiment, the spread value is determined by one of the following processes:

[0036] Add the distances between adjacent measurements,

[0037] Sum the distances of the measurements from the mean of the measurements of the stable variables.

[0038] In one embodiment, the distance metric A has the following relationship:

[0039] A=|p1–p2|^n, where n>0, p1 is the measured value, and p2 is the measured value or average value.

[0040] Preferably, n is a number greater than 0.5 and at most 4. It is not excluded here that the relationship has further terms or is modified by factors.

[0041] In one embodiment, a warning is output if the number of stable asymmetry value sequences exceeds a limit value. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will now be described with reference to exemplary embodiments.

[0043] Figure 1 An exemplary Coriolis measurement device is described;

[0044] Figure 2 An exemplary curve of the measurement signal is shown;

[0045] Figure 3 The sequence of the method according to the present invention is shown;

[0046] Figure 4 A curve showing a stable sequence of asymmetry values. DETAILED DESCRIPTION

[0047] Figure 1An exemplary Coriolis measuring device 1 for measuring the mass flow or density of a medium flowing through a pipeline is shown. The Coriolis measuring device comprises two measuring tubes 10, each having an inlet and an outlet 10.2. A measuring tube wall 10.4 encloses a measuring tube lumen 10.3. The measuring tubes are excited to vibrate by an exciter 11. A first sensor 12.1 on the inlet side and a second sensor 12.2 on the outlet side sense the vibrations and generate measurement signals, which are evaluated by electronic measuring / operating circuitry 77 disposed in a housing 80. The measuring tubes are held by a support element. As shown here, the sensor and exciter can each include a coil device 13 with a coil 13.1 and a magnetic device 14 with a magnet 14.1. The coil and magnetic devices undergo relative motion due to the vibration of the measuring tubes. As a result of this relative motion, a voltage is induced in the coils, generating a current that is processed by the electronic measuring / operating circuitry. The measurement signal can be either a voltage or a current. Because Coriolis measuring devices also exhibit inaccuracies during production and manufacturing, different sensors are not identical and, therefore, produce slightly different measurement signals under identical conditions, such as varying amplitudes. This asymmetry between sensors can be used as a further measurement variable to detect, for example, the operating state or wear of the Coriolis measuring device. As noted, the Coriolis measuring device may also include at least one temperature sensor 16 that detects the temperature of the measuring tube wall.

[0048] A Coriolis measuring device can also have just one measuring tube or more than two. A person skilled in the art will then adjust the exciter and sensor accordingly. Thus, the coil device and the magnetic device do not each have to be arranged on a measuring tube; they can also be fixed to a support element, for example, using a holding device. A Coriolis measuring device can also have more than one exciter and / or more than two sensors.

[0049] Figure 2 Example curves of the measurement signal are shown as a function of mass flow, density, sensor asymmetry, and measuring tube wall temperature. The scaling of the axes is given in arbitrary units and is provided for illustrative purposes only. In the case of homogeneous media, the curves for the measured density and flow rate typically vary slightly. In the case of media with different immiscible or poorly miscible components and / or components with different material states, short-term signal fluctuations with abrupt starts and stops may occur, as shown in the example measurement signal curves. This is because local fluctuations in the medium composition in the sensor area affect the measuring tube in different ways. During these phases, the asymmetry value sequence AS cannot be used.

[0050] Figure 3 A sequence of exemplary methods for stabilizing a sequence of asymmetric values according to the present invention is described.

[0051] In a first method step 101 , an asymmetry value sequence AS is created from the measurement signals from sensors 12 . 1 and 12 . 2 , wherein for example the amplitudes of the measurement signals from the sensors are used.

[0052] In a second method step 102 , a measurement signal of at least one stable variable is recorded, which measurement signal is used to determine the validity of the asymmetry value sequence.

[0053] In a third method step 103 , the asymmetry value sequence is stabilized by the stabilizing variable, and an asymmetry value sequence SAS is formed.

[0054] The first and second method steps can also be performed in reverse order or simultaneously. The order of the method steps is limited only by causal relationships. A stable variable is one of the following variables or its first or further time derivatives:

[0055] The resonant frequency of the measuring tube containing the medium or a variable derived therefrom, such as the density of the medium,

[0056] the time or phase difference between the measurement signals from the first sensor and the second sensor or a variable derived therefrom, such as mass flow,

[0057] Measure the temperature of the pipe wall,

[0058] Measure the temperature difference between two measuring points on the pipe wall.

[0059] For example, the dispersion of the measurement signal of the stable variable is determined, and when the dispersion value exceeds a first limit value, the last valid measured value of the asymmetry value sequence is used as the current value of the asymmetry measurement value, or the asymmetry value sequence is set to a predetermined value. In this way, the asymmetry value sequence can be prepared so that it can be interpreted and processed in a meaningful manner by, for example, electronic measuring / operating circuitry. Typical values for the predetermined value include NaN (Not a Number), 0, or a value outside the typical range of values for the asymmetry value sequence, such as 1000. This is what is meant by a stable asymmetry value sequence. The first limit value can be derived from the dispersion value of the measurement values of the stable variable and / or from the average value of the measurement values of the stable variable. When deriving the first limit value, the average value M can be a moving average value having a first time window Z1, and the dispersion value S can be a moving dispersion value having a second time window Z2, with these time windows being applied to the relevant measurement signal. For example, the first limit value can be defined as a relative or absolute minimum deviation from the average value. The dispersion can be calculated by summing the distances between adjacent measurement values within the time window Z2. It is also possible to form the sum of the distances of the measured values within the time window Z2 from a mean value in order to calculate the spread, wherein the mean value is formed from the measured values within the time window Z1 .

[0060] For example, the first time window Z1 has a duration of at least 0.2 seconds, in particular at least 0.5 seconds, and preferably at least 1 second, and / or the first time window has a duration of at most 90 seconds, in particular at most 70 seconds, and preferably at most 60 seconds. For example, the second time window Z2 has a duration of at least 2 seconds, in particular at least 4 seconds, and preferably at least 5 seconds, and / or the second time window has a duration of at most 150 seconds, in particular at most 130 seconds, and preferably at most 120 seconds. It is not excluded that the first time window and the second time window are identical.

[0061] The distance metric A can use the following relationship: A = |p1–p2|^n, where n>0, p1 is the measurement value, and p2 is the measurement value or average value.

[0062] Another reason for invalid measured values in an asymmetric value sequence can be that at least one measuring tube of a Coriolis measuring device is only partially filled. In this case, the amplitudes of the measurement signals from the sensors can differ significantly from one another. For example, if at least one measuring tube is oriented vertically, partial filling can occur when the liquid level in the measuring tube drops to a level between the first and second sensors due to a lack of flow. This can be detected by examining time or phase differences, or variables derived therefrom, along with the asymmetric value sequence.

[0063] If the time or phase difference or a variable derived therefrom is below a second limit value and the asymmetry exceeds a third limit value, partial filling is detected and the last valid measured value of the asymmetry value sequence is used as the current value of the asymmetry value sequence, or the asymmetry value sequence is set to a predetermined value.

[0064] Figure 4 An exemplary graph of measurement signals related to mass flow, density, sensor asymmetry, and measuring tube wall temperature is shown, where the asymmetry value sequence is now a stable asymmetry value sequence SAS. For example, time window Z1 (solid line) and time window Z2 (dashed line) are shown in the graph of measured values of the medium density, which were applied to the density measurement signal at a point in time and are performed at the current point in time. As a result of the process described further above, invalid measured values of the asymmetry value sequence can be detected and marked or corrected.

[0065] Typically, a warning may be output if the amount of the stable asymmetry value sequence SAS exceeds a fourth limit value G4. In this case, a degradation of the measurement system state may occur, which may require repair or replacement of the Coriolis measuring device. For example, the fourth limit value may be an asymmetry of at least 0.1%, particularly at least 1%, and preferably at least 5%.

[0066] Reference Mark List

[0067] 1 Coriolis measurement device

[0068] 10 Measuring tube

[0069] 10.2 Export

[0070] 10.3 Measuring Lumen

[0071] 10.4 Measuring the pipe wall

[0072] 11 Exciter

[0073] 12.1 First Sensor

[0074] 12.2 Second Sensor

[0075] 13 Coil equipment

[0076] 13.1 Coil

[0077] 14 Magnetic equipment

[0078] 14.1 Magnets

[0079] 16 Temperature Sensor

[0080] 60 Support elements

[0081] 77 Electronic measurement / operation circuits

[0082] 80 shell

[0083] 100 methods

[0084] 101 Methods and Steps

[0085] 102 Methods and Steps

[0086] 103 Methods and Steps

[0087] AS Asymmetric Value Sequence

[0088] SAS stable asymmetric value sequence

[0089] Z1 first time window

[0090] Z2 Second time window

Claims

1. A method (100) for operating a Coriolis measuring device (1) for measuring the density and / or mass flow of a medium flowing through a pipeline, in, The Coriolis measurement device comprises: at least one measuring tube (10) for guiding the medium, each measuring tube (10) having an inlet and an outlet (10.2) and a measuring tube wall (10.4) surrounding a measuring tube lumen (10.3); At least one exciter (11) for generating vibrations of the measuring tube, and a first sensor (12.1) on the inlet side and a second sensor (12.2) on the outlet side for sensing the vibrations of the measuring tube, wherein the exciter and the sensor each have a coil device (13) with at least one coil (13.1) and a magnetic device (14) with at least one magnet (14.1), wherein the coil device and the magnetic device of each sensor are moved relative to each other by vibration of the measuring tube, during which an electrical measuring voltage is induced in the coil; electronic measuring / operating circuitry (77) for operating the actuator, for sensing and evaluating the electrical measuring voltage, and for outputting measured values of the density and / or mass flow and diagnostic information, The method comprises the following steps: recording a measured voltage from the sensor and creating an asymmetry value sequence (AS) from the amplitude of the measured voltage for the purpose of diagnosing the Coriolis measuring device (101), recording a measurement signal of at least one stable variable (102), creating a stable asymmetric value sequence (SAS) based on the asymmetric value sequence according to said stable variable (103), where the spread of the measured values of the stable variable (S) is determined, wherein the sequence of asymmetric values is stabilized by the spread value, When the scatter value exceeds a first limit value, using the last valid measured value of the asymmetry value sequence as the current value of the asymmetry value sequence, or setting the asymmetric value sequence to a predetermined value, The spread value (S) is determined by one of the following processes: Add up the distances between adjacent measurements within the second time window (Z2), adding the distances of the measured values in the second time window (Z2) from a mean value, wherein the mean value is formed from the measured values in the first time window (Z1), The stable variable is based on one of the following variables or its first-order or second-order time derivative: the resonant frequency of the measuring tube containing the medium or a variable derived therefrom, a time or phase difference between the measurement signals from the first sensor and the second sensor, or a variable derived therefrom, The temperature of the measuring tube wall, The temperature difference between two measuring points on the measuring tube wall.

2. The method according to claim 1, in, The first limit value is derived from a scatter value and / or an average value of the measured values of the stable variable, Or wherein the first limit value is a configurable parameter.

3. The method according to claim 2, in, The average value is a moving average value having the first time window (Z1), and wherein the dispersion value is a moving dispersion value having the second time window (Z2).

4. The method according to claim 3, in, The first time window (Z1) has a duration of at least 0.2 seconds, and / or wherein, The first time window has a duration of at most 90 seconds.

5. The method according to claim 4, in, The first time window (Z1) has a duration of at least 0.5 seconds.

6. The method according to claim 5, in, The first time window (Z1) has a duration of at least 1 second.

7. The method according to claim 4, in, The first time window has a duration of at most 70 seconds.

8. The method according to claim 7, in, The first time window has a duration of at most 60 seconds.

9. The method according to claim 3, in, The second time window (Z2) has a duration of at least 2 seconds, and / or wherein the second time window has a duration of at most 150 seconds.

10. The method according to claim 9, in, The second time window (Z2) has a duration of at least 4 seconds.

11. The method according to claim 10, in, The second time window (Z2) has a duration of at least 5 seconds.

12. The method according to claim 9, in, The second time window has a duration of at most 130 seconds.

13. The method according to claim 12, in, The second time window has a duration of at most 120 seconds.

14. The method according to any one of claims 1 to 13, in, If the time or phase difference or a variable derived therefrom is below a second limit value and the asymmetry exceeds a third limit value, then using the last valid measured value of the asymmetry value sequence as the current value of the asymmetry value sequence, Alternatively, the asymmetry value sequence is set to a predetermined value.

15. The method according to claim 1, in, The distance metric A has the following relationship: A=|p1–p2|^n, where n>0, p1 is the measured value, and p2 is the measured value or average value.

16. The method according to any one of claims 1 to 13, in, If the amount of the stable asymmetry value sequence (SAS) exceeds a fourth limit value, a warning is output.

17. The method according to any one of claims 1 to 13, in, The Coriolis measuring device comprises at least one temperature sensor (16).

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