Method for calculating the mass of a measuring tube of a coriolis measuring device and the measuring device

Abstract

The present invention relates to a method (100) for calculating the mass associated with at least one measuring tube (11.1) of a Coriolis measuring device (10) for measuring the density or mass flow rate of a medium flowing through the measuring tube, wherein conclusions about the state of the measuring tube can be drawn by determining various vibration characteristics.

Description

Technical Field

[0001] This invention relates to a method for calculating the mass of a measuring tube of a Coriolis measuring device relative to wear or coating formation, and to such a measuring device. Background Technology

[0002] WO2010127951A1 discloses a method and a Coriolis measuring apparatus that, using this method and apparatus, back-calculates the current vibration characteristics of a measuring tube to standard vibration characteristics, and thereby determines the current wall thickness of the measuring tube. This allows, for example, the detection of wear on the measuring tube. The back-calculation requires consideration of various influences. In the prior art, the following variables are known to be relevant: medium temperature, support element temperature, casing temperature, and medium density. This document also provides those skilled in the art with basic physical knowledge regarding the vibration theory of the measuring tube in a Coriolis measuring apparatus.

[0003] However, it has been found that back-calculation based solely on existing technology is insufficient to meet high requirements, and in particular, wear can only be detected relatively late and preferably quantitatively determined. Summary of the Invention

[0004] Therefore, the object of the present invention is to determine the quality of the measuring tube so that this determination even meets high requirements.

[0005] This objective is achieved by the method and Coriolis measuring device according to the invention.

[0006] In the method according to the invention for calculating the mass associated with at least one measuring tube of a Coriolis measuring device, the Coriolis measuring device is used to measure the density or mass flow rate of the medium flowing through the measuring tube.

[0007] The Coriolis measuring device includes the following components:

[0008] A vibration system having at least one measuring tube for transmitting the medium.

[0009] The device comprises at least one exciter and at least two sensors, wherein the at least one exciter is designed to excite the vibration of a measuring tube, and the at least two sensors are used to detect the vibration of the measuring tube, and each of the exciter and / or sensors has at least one magnet device and one coil device.

[0010] A support element for supporting the at least one measuring tube.

[0011] An electronic device measurement / control circuit is designed to operate an actuator and to provide measurements of density and / or mass flow rate, and to perform the method.

[0012] An electronic device housing in which the electronic device's measurement / control circuitry is housed.

[0013] The method has at least the following steps:

[0014] Associate at least one excitation input variable of at least one exciter with at least one output variable of at least one sensor.

[0015] The current vibration characteristics of the vibration system are determined based on the vibration model and correlation of the measuring tube.

[0016] Determine the standard vibration characteristics of the measuring tube under standard conditions from the current vibration characteristics of the vibration system.

[0017] in,

[0018] In at least one method step, at least one of the following variables is used:

[0019] Nonlinear contribution of at least one of the following temperatures: medium temperature, support element temperature, and housing temperature;

[0020] Medium pressure;

[0021] The cumulative time during which the magnet device is exposed to a temperature above the corresponding threshold temperature;

[0022] Medium viscosity.

[0023] By determining the standard vibration characteristics according to the present invention, the standard vibration characteristics of the measuring tube can be determined more accurately because the effects of subtle disturbances are now corrected.

[0024] For example, increased medium pressure leads to an increase in the diameter of the measuring tube, thereby changing the stiffness of the measuring tube. Without considering the medium pressure, the determination of the standard vibration characteristics would be incorrect.

[0025] It has been found that, considering the current technology, the temperature is not satisfactory.

[0026] The permanent magnets in a magnet device are susceptible to high temperatures, which can cause or accelerate a decrease in their magnetization. This sensitivity increases significantly above a threshold temperature, which is highly material-dependent. Several threshold temperatures may also exist above which aging increases. Those skilled in the art can determine these threshold temperatures of the permanent magnets. If the permanent magnets of a sensor or actuator are damaged due to high temperatures, in the case of an actuator, the excitation current will generate a smaller excitation magnetic field, resulting in a smaller amplitude of vibration in the measuring tube. In the case of a sensor, this damage leads to a lower voltage sensing of the measured voltage. The determination of standard vibration characteristics would be incorrect if temperature-dependent or aging-dependent damage to the permanent magnets were not considered.

[0027] In one improved embodiment, when using the medium temperature and / or the support element temperature and / or the housing temperature, a first set of temperature coefficients or a second set of temperature coefficients is used.

[0028] If the medium temperature is higher than the limiting temperature, then the first set of temperature coefficients is used.

[0029] If the medium temperature is below the limiting temperature, then the second set of temperature coefficients is used.

[0030] The vibration characteristics of the measuring tube are affected by material properties—such as the elastic modulus or coefficient of thermal expansion of the measuring tube and / or the support element and / or the housing. The support element and / or housing can affect the measuring tube via a bearing point, for example, via clamping force. These material properties—i.e., elastic modulus, for example—are temperature-dependent, and thus, in precise measuring devices, such as Coriolis measuring devices, this temperature dependence must be considered. This is typically accomplished through mathematical models, where, for example, polynomial functions with corresponding coefficients up to order n are applied, where n is a natural number. As n increases, determining the coefficients becomes more difficult and inaccurate. According to the invention, the operating temperature range of the Coriolis measuring device to be used is therefore divided into at least two ranges, each separated by a limiting temperature, and slightly lower-order models with their own coefficients are used in these ranges respectively. In this way, the workload for determining the higher-order coefficients can be limited.

[0031] For example, such a limit temperature could be set between -50°C and +50°C, that is, even, for example, at 0°C. However, this information is to be interpreted as an example only and not a limitation.

[0032] This process is not limited to using polynomial functions. Those skilled in the art can choose at least one family of functions to create a mathematical model according to their needs.

[0033] This process is not limited to dividing the operating temperature range into two ranges separated by extreme temperatures. The operating temperature range can also be divided into more than two ranges, with adjacent ranges separated by extreme temperatures.

[0034] In an improved scheme, at least one of the following variables is additionally used to calculate the standard vibration characteristics:

[0035] At least one of the following temperatures: medium temperature, support element temperature, housing temperature, actuator temperature, sensor temperature;

[0036] Medium density and / or the square of the medium density;

[0037] Each of the listed temperatures potentially affects the measurement of the vibration characteristics of the measuring tube. The temperature of the housing or the support element affects the clamping or securing of the measuring tube; for example, the temperature of the exciter or the sensor affects the ohmic resistance of the coil system, and thus the efficiency of excitation or detection of the measuring tube's vibration.

[0038] The density of the medium affects the total mass of the vibrating system, and thus the resonant frequency of the vibrating system.

[0039] In one improved embodiment, at least a first accumulation time is measured relative to a first threshold temperature, and a second accumulation time is measured relative to a second threshold temperature and used to calculate standard vibration characteristics. In this case, the use of more threshold temperatures and more accumulation times is not excluded. For example, materials that can be used as permanent magnets can have multiple threshold temperatures at which the over-aging, aging, or damage of the permanent magnet occurs, for example, more rapidly. These threshold temperatures are material-dependent. Therefore, those skilled in the art will be specifically informed of these threshold temperatures, or they will be determined, for example, by testing.

[0040] In one improved scheme, at least one cumulative time is the independent variable of a nonlinear, monotonic, and particularly decreasing function, which can be described, for example, by a logarithmic function, a root function, or an exponential function.

[0041] In an improved embodiment, the medium temperature and / or the support element temperature and / or the housing temperature are each determined by at least one temperature sensor provided for this purpose.

[0042] In one improved embodiment, the elastic modulus of the outer wall of the measuring tube, support element, or electronic device housing is used to determine the temperature coefficient in the set of temperature coefficients.

[0043] In an improved scheme, the nonlinear contribution may be, for example, a quadratic, logarithmic, potential, or exponential contribution.

[0044] In one improved approach, the method includes the following steps:

[0045] The standard vibration characteristics are compared with reference vibration characteristics, which are determined, for example, through operational calibration or factory calibration under standard conditions.

[0046] In one improved approach, the method includes the following steps:

[0047] Observe the time progression of standard vibration characteristics.

[0048] A warning message will be output if the following occurs:

[0049] The standard vibration characteristics have minimal deviation from the reference vibration characteristics.

[0050] The value of the rate of change of the standard vibration characteristics exceeds the minimum value.

[0051] In one improved scheme, the vibration characteristic is modal stiffness.

[0052] In one improved scheme, the vibration model is formed with up to second-order degrees of freedom that can be applied.

[0053] In particular, this vibration model has components. in,

[0054] F D It is an excitation force applied by at least one exciter to at least one measuring tube and forming an excitation input variable.

[0055] X S The vibration amplitude of the vibration system caused by the exciter forms a response variable that is related to the sensor's output variable AG, where the correlation may depend on the state of the permanent magnet, such as its aging state.

[0056] 'a' is a material- and geometry-dependent constant of at least one measuring tube.

[0057] h is the wall thickness of at least one measuring tube.

[0058] ω0 is the resonant frequency of the vibration modes under separate excitation.

[0059] Q is the mass factor, which describes the damping behavior of the vibration of the system during a single excitation.

[0060] s = iω, where ω corresponds to the excitation frequency of the vibration system.

[0061] as well as

[0062] Wherein, the product of a and h is a measure of the modal stiffness of at least one measuring tube.

[0063] The Coriolis measuring device according to the invention, designed to perform the method according to the invention, comprises:

[0064] A vibration system having at least one measuring tube for transmitting the medium.

[0065] The device includes at least one exciter and at least two sensors. The at least one exciter is designed to excite the vibration of a measuring tube, and the at least two sensors are used to detect the vibration of the measuring tube. Each of the exciter and / or sensors has at least one magnet device with a permanent magnet and a coil device.

[0066] A support element for supporting the at least one measuring tube.

[0067] An electronic device measurement / control circuit is designed to operate an actuator and to provide measurements of density and / or mass flow rate, and to perform the method.

[0068] The electronic device housing contains the electronic device's measurement / control circuitry.

[0069] In one improved embodiment, the Coriolis measuring device has at least one temperature sensor, which is designed to measure at least one of the following temperatures:

[0070] Medium temperature, support element temperature, housing temperature, actuator temperature, sensor temperature. Attached Figure Description

[0071] The invention will now be described with reference to exemplary embodiments.

[0072] Figure 1 The structure of an exemplary Coriolis measurement device with an exemplary Coriolis measurement transducer is described;

[0073] Figure 2 A sequence of methods according to the present invention is described. Detailed Implementation

[0074] Figure 1 The structure of an exemplary Coriolis measuring device 10 according to the invention is shown. This device has an exemplary Coriolis measuring transducer according to the invention, which has a vibration system having two measuring tubes 11, a support element 12, an exciter 13, and two sensors 14. Each measuring tube has an inlet and an outlet. The support element supports the measuring tube. The exciter is designed to excite the two measuring tubes to vibrate perpendicular to the longitudinal plane of the measuring tube defined by the curved measuring tube. The sensors are designed to detect the vibration applied to the measuring tubes. A temperature sensor 17 is designed to detect the temperature of the support element of the measuring tube (affected by the medium temperature) and the temperature of the support element itself. Such temperature sensors may also be mounted on the sensors and exciter. The Coriolis measuring transducer is connected to an electronics housing 80 of the Coriolis measuring device, which is designed to house an electronics measurement / control circuit 77. This circuit is designed to operate the exciter and sensors and determine and provide flow rate and / or density values ​​based on the vibration characteristics of the measuring tubes measured by the sensors. The actuator and sensor are connected to the electronic measurement / control circuit via electrical connector 19. Electrical connector 19 can be bundled with a cable guide in each case.

[0075] The Coriolis measuring instrument according to the present invention is not limited to the presence of two measuring tubes. Therefore, the present invention can be implemented in Coriolis measuring devices having any number of measuring tubes, for example, in single-tube or four-tube measuring devices.

[0076] Unlike what is shown here, these measuring tubes can also be straight, for example, designed to perform lateral or torsional vibrations.

[0077] When operating such a Coriolis measuring device, many effects must be considered. The exciter efficiency correspondingly affects the amplitude of the measuring tube's vibration, and the sensor sensitivity affects the ability to convert the tube's vibration into a measured variable (e.g., a measured voltage or current). Coriolis measuring devices are typically calibrated under standard conditions before startup, for example, at the manufacturer's customer's facility, specifically to establish the correlation between the excitation of the measuring tube's vibration by the exciter and the detection of that vibration by the sensor. The exciter efficiency and sensor sensitivity are affected, and these effects can lead to both reversible and irreversible changes in these variables.

[0078] An example of a reversible effect is the increase in ohmic resistance of the sensor's coil assembly due to increased temperature within the coil assembly, which leads to a decrease in voltage induction by the sensor magnet moving relative to the coil assembly. An example of an irreversible change is, for example, aging of the sensor magnet due to intense heating. Corresponding similar effects can occur depending on the actual design of the sensor (e.g., optical sensors) or actuator.

[0079] Therefore, in order to accurately measure mass flow rate and / or density and monitor aging or condition, a suitable method for operating Coriolis measuring devices is needed.

[0080] Figure 2 A sequence of exemplary methods according to the present invention for calculating the mass associated with at least one measuring tube 11.1 of a Coriolis measuring apparatus is described.

[0081] In step 101 of the first method, at least one excitation input variable AEG of at least one exciter is associated with at least one output variable AG of at least one sensor, and

[0082] In step 102 of the second method, the current vibration characteristics (ASE) of at least one measuring tube are determined based on the vibration model of the measuring tube and the correlation.

[0083] In step 103 of the third method, the standard vibration characteristics SSE of the measuring tube under standard conditions are determined based on the current vibration characteristics of the measuring tube.

[0084] In at least one method step, at least one of the following variables is used:

[0085] Nonlinear contribution of at least one of the following temperatures: medium temperature, support element temperature, and housing temperature;

[0086] Medium pressure;

[0087] The cumulative time during which the magnet device is exposed to a temperature above the corresponding threshold temperature;

[0088] Medium viscosity.

[0089] By determining the standard vibration characteristics according to the present invention, the standard vibration characteristics of the measuring tube can be determined more accurately because the effects of subtle disturbances are now corrected.

[0090] like Figure 2 As shown, this method may have further method steps.

[0091] Therefore, the method shown here includes the following method steps:

[0092] In step 104 of the fourth method, a standard vibration characteristic is compared with a reference vibration characteristic, RSE, which is determined, for example, by operational calibration or factory calibration under standard conditions.

[0093] In step 105 of the fifth method, observe the time evolution of the standard vibration characteristics.

[0094] In step 106 of the sixth method, a warning message is output if the following occurs:

[0095] The standard vibration characteristic SSE has minimal deviation from the reference vibration characteristic RSE.

[0096] The value of the rate of change of the standard vibration characteristics exceeds the minimum value.

[0097] In this way, customers and / or manufacturers of such Coriolis measuring devices can be notified that the measuring tube of the Coriolis measuring device is unreliable or in poor condition due to abrasion or coating formation, and timely replacement or cleaning can be ensured.

[0098] Therefore, the standard vibration characteristic SSE can be expressed in an abstract way, for example, through the following equation:

[0099] SSE=ASE*K_temp*K_density*K_pressure*K_aging*K_visc,

[0100] The constant linear and nonlinear effects can be used in the correction term K as described above. Those skilled in the art can quantify these effects in a Coriolis measurement device and determine the corresponding coefficients for these effects.

[0101] For example, the correction term K_temp can be defined as follows:

[0102] K_temp = C1 + K1*T_med + K2*(T_med)^2, where T_med is the medium temperature, C1 is a constant, K1 is the first coefficient, and K2 is the second coefficient. This also applies to the correction terms for the temperature of the supporting element or the housing temperature. The nonlinear term here is quadratic, but it can have any other desired nonlinear form, and therefore can contribute logarithmically, potential-wise, or exponentially, for example.

[0103] Similarly, correction terms can be formatted with respect to variables such as the density, pressure, viscosity, and aging of the permanent magnet using their own coefficients. For example, as the permanent magnet ages, aging can be described using a logarithmic, root, or exponential function as a decreasing function, where at least one cumulative time the magnet device has been exposed to temperatures above a corresponding threshold temperature is included as an independent variable in the function in each case. An example of using a function with an exponential function to describe aging is as follows: C² - K³ * exp(-x * K₄ + K₅), where x is the variable for cumulative time, C² is a constant, and K₃ to K₅ are coefficients.

[0104] The description of the relationship between SSE and ASE presented here is to be interpreted as an example and not a limitation.

[0105] List of reference numerals

[0106] 10 Coriolis measuring device

[0107] 11 Vibration System

[0108] 11.1 Measuring tube

[0109] 12 Support elements

[0110] 13 Exciter

[0111] 14 Sensors

[0112] 15. Magnet device

[0113] 16. Coil assembly

[0114] 17 Temperature sensor

[0115] 19 Electrical connections

[0116] 77 Electronic Device Measurement / Control Circuits

[0117] 80 Electronic device housings

[0118] 100 methods

[0119] Methods and steps 101-106

[0120] AEG stimulus input variables

[0121] AG output variables

[0122] ASE Current Vibration Characteristics

[0123] SSE Standard Vibration Characteristics

[0124] RSE Reference Vibration Characteristics

Claims

1. A method (100) for calculating a mass related to at least one measuring tube (11.1) of a Coriolis measuring device (10) for measuring a density or a mass flow rate of a medium flowing through the measuring tube, the Coriolis measuring device having the following components: a vibrating system (11) having at least one measuring tube (11.1) for conducting the medium, at least one exciter (13) designed to excite the measuring tube to vibrate and at least two sensors (14) for detecting the measuring tube vibrations, the exciter and the sensors each having at least one magnet arrangement (15) with permanent magnets and one coil arrangement (16), a support element (12) for supporting the at least one measuring tube, an electronics measuring / control circuit (77) designed to operate the exciter and to provide a measured value of the density and / or mass flow rate and to perform the method, an electronics housing (80) in which the electronics measuring / control circuit is arranged, the method (100) having at least the following steps: associating (101) at least one excitation input variable of the at least one exciter with at least one output variable of at least one sensor, determining (102) a current vibration behavior of the vibrating system based on a vibration model of the measuring tube and the association, determining (103) a standard vibration behavior of the measuring tube under standard conditions from the current vibration behavior of the vibrating system, characterized in that in at least one method step, at least one of the following variables is used: a non-linear contribution of at least one of the following temperatures: medium temperature, support element temperature, housing temperature; medium pressure; at least one accumulation time during which the magnet arrangement is exposed to a temperature above a respective threshold temperature; medium viscosity; wherein at least one of the following variables is additionally used for calculating the standard vibration behavior: medium temperature, support element temperature, housing temperature, exciter temperature, sensor temperature; medium density and / or square of the medium density; and wherein a first accumulation time is measured with respect to a first threshold temperature and a second accumulation time is measured with respect to a second threshold temperature and is used for calculating the standard vibration behavior.

2. The method according to claim 1, wherein, when using the medium temperature and / or the support element temperature and / or the housing temperature, using a first set of temperature coefficients or a second set of temperature coefficients, wherein the first set of temperature coefficients is used if the medium temperature is above a limit temperature, wherein the second set of temperature coefficients is used if the medium temperature is below the limit temperature.

3. The method according to claim 1, wherein the at least one accumulation time is in each case an argument of a non-linear, monotonic and decreasing function, wherein the function is described by a logarithmic function or a root function or an exponential function.

4. The method according to claim 1, wherein the medium temperature and / or the support element temperature and / or the housing temperature are determined by at least one temperature sensor provided for this purpose, respectively.

5. The method according to any one of claims 2 to 4, wherein the modulus of elasticity of the measuring tube or of the support element or of the housing wall of the electronics housing is used to determine a temperature coefficient of the set of temperature coefficients.

6. The method according to any one of claims 1 to 4, wherein, the non-linear contribution is a quadratic, logarithmic, potential or exponential contribution.

7. The method according to any one of claims 1 to 4, wherein the method comprises the following method steps: comparing the standard vibration characteristic with a reference vibration characteristic (104), the reference vibration characteristic being determined by an operation calibration or a factory calibration under standard conditions.

8. The method according to any one of claims 1 to 4, wherein, the method comprises the following method steps: observing the time progression of the standard vibration characteristic (105), and outputting a warning message (106) if: the standard vibration characteristic has a minimum deviation from a reference vibration characteristic, and / or the value of the rate of change of the standard vibration characteristic exceeds a minimum value.

9. The method according to any one of claims 1 to 4, wherein the vibration characteristic is a modal stiffness.

10. The method according to claim 9, wherein the vibration model is formed with a degree of freedom applied up to the second order, The vibration model has components wherein, F D is an excitation force applied by the at least one exciter on the at least one measurement tube and forming the excitation input variable, X S is an amplitude of vibration of the vibration system caused by the exciter, the amplitude of vibration forming a response variable, a is a material-dependent and geometry-dependent constant of the at least one measuring tube, h is the tube wall thickness of the at least one measuring tube, ω0is the resonance frequency of the respectively excited vibration mode, Q is a quality factor, which describes the decay behavior of the vibrations of the vibration system during a single excitation, and s = iω, wherein ω corresponds to the excitation frequency of the vibration system, and wherein the product of a and h is a measure of the modal stiffness of the at least one measuring tube.

11. A Coriolis measuring device (10) designed to carry out the method according to any one of claims 1 to 10, comprising: a vibration system (11) with at least one measuring tube (11.1) for conducting the medium, at least one exciter (13) designed to excite the measuring tube vibrations and at least two sensors (14) for detecting the measuring tube vibrations, the exciter and the sensors each having at least one magnet arrangement (15) with permanent magnets and one coil arrangement (16), a support element (12) for supporting the at least one measuring tube, an electronics measuring / control circuit (77) designed to operate the exciter and to provide a measured value of the density and / or mass flow rate and to carry out the method, an electronics housing (80) in which the electronics measuring / control circuit is arranged.

12. The Coriolis measuring device according to claim 11, wherein The Coriolis measuring device (10) has at least one temperature sensor (17) which is designed to measure at least one of the following temperatures: Medium temperature, support element temperature, housing temperature, exciter temperature, sensor temperature.

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