Method for testing a coriolis mass flowmeter
Patent Information
- Application Number
- EP2023801351
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-11-03
- Filing Date
- 2023-11-02
- Publication Date
- 2025-09-10
AI Technical Summary
Coriolis mass flowmeters face inaccuracies and unreliable operation due to changes in alignment or damage of drive and sensor electromagnets, caused by vibrations, external mechanical influences, or aging, leading to incorrect mass flow determination.
A method that involves measuring a device parameter quotient of drive and sensor voltages induced by measuring tube vibrations, using a test drive signal with a frequency different from natural frequencies, and comparing it to a stored value to detect deviations, thereby identifying misalignment or damage.
This method ensures accurate detection of alignment changes or damage, preventing inaccurate mass flow determination and ensuring reliable operation by continuously monitoring the Coriolis mass flowmeter.
Smart Images
Figure 1.1
Abstract
Description
[0001] Procedure for testing a Coriolis mass flowmeter
[0002] The invention relates to a method for testing a Coriolis mass flowmeter.
[0003] The Coriolis mass flowmeter comprises a measuring tube, at least one drive electromagnet, at least one sensor electromagnet and a controller. The at least one drive electromagnet comprises a drive coil and a drive coil core, and the at least one sensor electromagnet comprises a sensor coil and a sensor coil core.
[0004] The controller is configured to excite a measuring vibration of the measuring tube by generating and feeding a measuring drive signal into the at least one drive coil. It is further configured to determine a mass flow of a medium through the measuring tube using an electrical measuring sensor signal from the at least one sensor coil caused by the measuring vibration.
[0005] If the Coriolis mass flowmeter has more than one drive electromagnet, each drive electromagnet has a drive coil and a drive coil core, and the measurement drive signal is fed into each of the drive electromagnets. For this purpose, the drive coils are, for example, electrically connected in series. If the Coriolis mass flowmeter has more than one sensor electromagnet, each sensor electromagnet has a sensor coil and a sensor coil core, and the measurement sensor signal is usually determined from signals at each of the sensor coils.
[0006] By feeding a drive signal into the at least one drive coil, a drive force is created between the drive coil and the drive coil core of the at least one drive electromagnet. The drive coil and the drive coil core of the at least one drive electromagnet are arranged on the Coriolis mass flowmeter in such a way that the drive force is transmitted to the measuring tube. The drive force transmitted to the measuring tube usually causes the measuring tube to oscillate. The oscillation of the measuring tube causes the drive coil and the drive coil core of the at least one drive electromagnet to move relative to one another. The sensor coil and the sensor coil core of the at least one sensor electromagnet are arranged on the Coriolis mass flowmeter in such a way that the oscillation of the measuring tube also causes the sensor coil and the sensor coil core to move relative to one another.In this way, the movement causes an electrical sensor signal in the at least one sensor coil by induction.
[0007] If the drive signal is the measurement drive signal, then the vibration is the measurement vibration, and the sensor signal is the measurement sensor signal. The controller uses the measurement sensor signal to determine the mass flow of the medium through the measuring tube.
[0008] For reliable operation and accurate determination of the mass flow rate, it is essential that a specific alignment of the drive coil and the drive coil core of the at least one drive electromagnet and the sensor coil and the sensor coil core of the at least one sensor electromagnet is maintained, and that no damage is present to the at least one drive electromagnet and the at least one sensor electromagnet. Vibrations, external mechanical influences, or aging can alter the alignment or cause damage. Altered alignment or damage ultimately results in a less accurate determination of the mass flow rate.Further adverse consequences include, for example, unreliable operation, no excitation of the measuring oscillation despite the measuring excitation signal, incorrect density measurement or increased current through the drive coil to excite the measuring oscillation.
[0009] The object of the present invention is to provide a method for testing a Coriolis mass flowmeter which detects a changed alignment and / or damage.
[0010] The problem is solved by a method having the features of claim 1.
[0011] The method is characterized in that a value of a device parameter is first stored in the controller. The device parameter is a quotient of a drive voltage and a sensor voltage. The drive voltage is induced by the drive coil core into the drive coil of the at least one drive electromagnet, and the sensor voltage is induced by the sensor coil core into the sensor coil of the at least one sensor electromagnet. The induced drive voltage and the induced sensor voltage are caused by an oscillation of the measuring tube.
[0012] The method is further characterized in that the control system executes a test function with the following steps during operation of the Coriolis mass flowmeter:
[0013] In one method step, a test drive signal is generated with a test drive frequency that differs from the natural frequencies of the measuring tube and fed into the at least one drive coil. The test drive signal therefore has no natural frequency of the measuring tube. This ensures that a vibration of the measuring tube caused by the test drive signal has only a small vibration amplitude relative to the amplitude of the test drive signal, compared to a drive signal that has a natural frequency of the measuring tube.
[0014] In one method step, a test drive voltage across the at least one drive coil and a test drive current through the at least one drive coil are measured. The test drive voltage and the test drive current are measured while the test drive signal is fed into the at least one drive coil. The oscillation of the measuring tube causes a movement of the at least one drive coil and the at least one drive coil core relative to one another. The same applies to the at least one sensor coil and the at least one sensor coil core. Since the oscillation amplitude of the measuring tube is small, the amplitude of the drive voltage induced in the at least one drive coil by the movement is also small. Thus, the amplitude of the induced drive voltage is small relative to the amplitude of the test drive signal.
[0015] In one method step, a drive electromagnetic impedance is determined using the test drive voltage and the test drive current. Since the amplitude of the induced drive voltage is small relative to the amplitude of the test drive signal, any inaccuracy in the determined drive electromagnetic impedance caused by the induced drive voltage is also small.
[0016] In one method step, the measurement drive signal is generated and fed into the at least one drive coil. In one method step, a measurement drive voltage across the at least one drive coil, a measurement drive current through the at least one drive coil, and a measurement sensor voltage across the at least one sensor coil are measured. The measurement drive voltage, the measurement drive current, and the measurement sensor voltage are measured while the measurement drive signal is fed into the at least one drive coil. Preferably, the test drive signal and / or the measurement drive signal are sinusoidal signals.
[0017] In one process step, a value of the device parameter is determined using the drive electromagnetic impedance, the measuring drive voltage, the measuring drive current and the measuring sensor voltage.
[0018] After executing the test function, the controller signals an error if the deviation between the specified value of the device parameter and the stored value of the device parameter is greater than a limit value stored in the controller. The deviation is determined by the controller.
[0019] The basis is the following finding: If the measuring tube oscillates, the drive coil core induces a drive voltage into the drive coil of the at least one drive electromagnet, and the sensor coil core induces a sensor voltage into the sensor coil of the at least one sensor electromagnet. The quotient of the drive voltage and the sensor voltage is constant in a Coriolis mass flowmeter if the alignment has not changed and no damage has occurred. For the quotient to be constant, other boundary conditions must also be constant or taken into account. One such further boundary condition is a temperature of the at least one drive electromagnet and / or the at least one sensor electromagnet. Here, it is assumed that the boundary conditions are constant.
[0020] Accordingly, the method enables the detection of a changed alignment and / or damage.
[0021] In one embodiment of the method, the device parameter is determined using the following formula: The measuring drive voltage is equal to a sum of, on the one hand, a product of the drive electromagnetic impedance and the measuring drive current, and, on the other hand, a product of the device parameter and the measuring sensor voltage. The formula is then solved for the device parameter. In a further embodiment, the stored value of the device parameter is determined by the controller itself by executing the test function, or the stored value of the device parameter is determined by a simulation of the Coriolis mass flowmeter. Before executing the test function to determine the value of the subsequently stored device parameter, it is ensured in particular that the specific alignment and no damage is present. The simulation takes into account in particular the amplitude of the measuring vibration and the alignment.It also considers the resistance, inductance, dimensions, and number of turns of the drive coils and sensor coils. Furthermore, if permanent magnets are used as coil cores, it also considers their magnetic field strengths.
[0022] In a further embodiment, the test drive signal and the measurement drive signal are generated and applied simultaneously. Accordingly, the test drive voltage, the test drive current, the measurement drive voltage, the measurement drive current, and the measurement sensor voltage are measured simultaneously. The test drive voltage and the test drive current, on the one hand, and the measurement drive voltage, the measurement drive current, and the measurement sensor voltage, on the other, are differentiated by the controller based on their different frequency contents.
[0023] In a further embodiment, the measurement drive signal has a natural frequency of the measuring tube. By exciting the measuring tube to oscillate at a natural frequency of the measuring tube, the power required for the oscillation is reduced compared to exciting the measuring tube at a frequency different from the natural frequency.
[0024] In a further embodiment, the controller determines the mass flow of a medium through the measuring tube using the measuring drive voltage and the measuring sensor voltage. The measuring sensor voltage is thus the measuring sensor signal. This embodiment reduces time loss due to the test function, since the measured values required for the test function are also used to determine the flow rate.
[0025] In a further embodiment, the test function is executed periodically during operation of the Coriolis mass flowmeter and / or when the Coriolis mass flowmeter switches to a measuring mode and / or when the Coriolis mass flowmeter is started. By periodically executing the test function, the Coriolis mass flowmeter is continuously monitored. By executing the test function at startup, a deviation in alignment or damage is detected immediately upon startup. In measuring mode, the Coriolis mass flowmeter determines the mass flow of a medium through the measuring tube.
[0026] In a further embodiment, the execution of the test function is triggered manually by a user.
[0027] A further embodiment requires that the Coriolis mass flowmeter has two sensor electromagnets. In one embodiment of the method for this Coriolis mass flowmeter, the measuring sensor voltage is determined by measuring a first measuring voltage across the sensor coil of one of the two sensor electromagnets and a second measuring voltage across the sensor coil of the other of the two sensor electromagnets. The measuring sensor voltage is then determined as an average of the first measuring voltage and the second measuring voltage.
[0028] In a further embodiment, the controller stores the specific value of the device parameter in a datum. Furthermore, a timestamp and / or metadata is preferably also stored in the datum, and the datum is provided for error diagnosis. This is also performed by the controller.
[0029] In a further development of the above embodiment, the metadata includes a temperature and / or a mass flow.
[0030] In a further embodiment of the method, the controller adds the date to a list of stored historical data and makes the list available for diagnosing the error.
[0031] In detail, there are numerous possibilities for designing and developing the method for testing a Coriolis mass flowmeter. Reference is made, firstly, to the claims subordinate to the independent claim and, secondly, to the following description of a preferred embodiment in conjunction with the drawing. The drawing shows:
[0032] Fig. 1 An embodiment of a Coriolis mass flow meter, Fig. 2 a deflection of the measuring tube of the Coriolis mass flow meter and
[0033] Fig. 3 is a flowchart of an embodiment of a method for testing the Coriolis mass flowmeter.
[0034] Figure 1 shows a Coriolis mass flowmeter 1. This comprises a measuring tube 2, a drive electromagnet 3, two sensor electromagnets 4, and a controller 5. The drive electromagnet 3 has a drive coil 6 and a drive coil core 7. Each of the two sensor electromagnets 4 has a sensor coil 8 and a sensor coil core 9. The coil core of a coil can be a permanent magnet. Here, both the drive coil core 7 and the sensor coil cores 9 are permanent magnets.
[0035] The measuring tube 2 has a longitudinal axis 10 and is supported at its ends in bearings 11. In the measuring tube 2 is a medium 12, which flows at a speed v M flows through the measuring tube 2 in the direction of the arrow.
[0036] Figure 2 shows a deflection s of the measuring tube 2 along the longitudinal axis 10 at a specific time. At this time, the deflection in a center between the bearings 11 has a velocity v s in the direction of the arrow. The bearings 11 prevent deflection of the measuring tube 2 at the bearings 11, but allow deflection between the bearings 11. The solid line of the longitudinal axis 10 shows the deflection of the measuring tube 2 when the medium 12 in the measuring tube 2 is stationary, i.e. the velocity v M = 0. The dashed line of the longitudinal axis 10 shows the deflection of the measuring tube 2 when the medium 12 passes the measuring tube 2 with a speed v M > 0 is flowed.
[0037] A key feature of the method is a device parameter k. The device parameter k is generally a quotient of a drive voltage induced into a drive coil by a drive coil core and a sensor voltage induced into a sensor coil by a sensor coil core. The induced drive voltage and the induced sensor voltage are caused by an oscillation of a measuring tube of a Coriolis mass flowmeter. Since the Coriolis mass flowmeter 1 in this exemplary embodiment has two sensor electromagnets 4, there are correspondingly also two device parameters k. Consequently, for a Coriolis mass flowmeter with three sensor electromagnets 4, there are three device parameters k. The same applies if a Coriolis mass flowmeter has more than one drive electromagnet.In an alternative embodiment, the Coriolis mass flowmeter 1 has more than one drive electromagnet 3, and the drive coils 6 are electrically connected in series. In principle, the device parameter k refers to one of the drive electromagnets and one of the sensor electromagnets of a Coriolis mass flowmeter. In the following, the device parameter k is described only for the drive electromagnet 3 and one of the two sensor electromagnets 4 in this embodiment. The device parameter k is therefore a quotient of a drive voltage induced by the drive coil core 7 in the drive coil 6 and a sensor voltage induced by the sensor coil core 9 in the sensor coil 8. The induced drive voltage and the induced sensor voltage are caused by an oscillation of the measuring tube 2.
[0038] The controller 5 is designed to carry out the following process steps, see Figure 3, and also carries them out since the Coriolis mass flow meter 1 is in operation:
[0039] In a first method step 101, a value of the device parameter k for the drive electromagnet 3 and one of the two sensor electromagnets 4 is stored in the controller 5.
[0040] In a second method step 102, a test drive signal is generated and fed into the drive coil 6. The test drive signal has a test drive frequency that differs from the natural frequencies of the measuring tube 2.
[0041] In a third method step 103, a test drive voltage U T across the drive coil 6 and a test drive current I T measured by the drive coil 6. The test drive signal is applied to the drive coil 6.
[0042] In a fourth method step 104, a drive electromagnetic impedance Z is determined using the test drive voltage U T and the test drive current I T determined according to the formula Z = U T / IT
[0043] In a fifth method step 105, a measuring drive signal is generated and fed into the drive coil 6. The measuring drive signal has a natural frequency of the measuring tube 2. In a sixth method step 106, a measuring drive voltage U A across the drive coil 6 and a measuring drive current I A measured by the drive coil 6 and a measuring sensor voltage U s across the sensor coil 8. Determining the measuring sensor voltage U s In this embodiment, the measurement is carried out by measuring. In an alternative embodiment, the measuring sensor voltage U sdetermined by measuring a first measuring voltage across the sensor coil 8 of one of the two sensor electromagnets 4 and a second measuring voltage across the sensor coil 8 of the other of the two sensor electromagnets 4 and then determining the measuring sensor voltage Us as an average value of the first measuring voltage and the second measuring voltage.
[0044] In this embodiment, in a seventh method step 107, a value of the device parameter k is determined using the drive electromagnetic impedance Z, the measuring drive voltage U A , the measuring drive current I A and the measuring sensor voltage U s In this embodiment, the device parameter k is determined using the following formula:
[0045] U A = Z - I A + k - U s
[0046] In words: The measuring drive voltage U Ais equal to the sum of the product of the drive electromagnetic impedance Z and the measuring drive current I A and the product of the device parameter k and the measuring sensor voltage U s . The formula is solved for k.
[0047] Typically, the drive voltage, drive current, and sensor voltage are determined as complex quantities. Thus, the test drive voltage U T , the test drive current I T , the measuring drive voltage U A , the measuring drive current I A and the measuring sensor voltage U s and consequently also the drive electromagnetic impedance Z and the device parameter k are complex values.
[0048] Furthermore, a mass flow of the medium 12 through the measuring tube 2 is determined by the controller 5 using the measuring drive voltage U A and the measuring sensor voltage U sThe determined value of the device parameter k is stored in a datum along with a timestamp and metadata. The metadata is a temperature and the determined flow rate. In an eighth method step 108, an error is signaled if a deviation of the determined value of the device parameter k from the stored value of the device parameter is greater than a limit value stored in the controller 5. The previously stored datum is provided for error diagnosis.
[0049] Method steps two to seven form a test function with which the Coriolis mass flowmeter is tested. In this exemplary embodiment, the test function is executed upon startup and then periodically during operation of the Coriolis mass flowmeter 1. Alternatively, the test function is executed when the Coriolis mass flowmeter 1 switches to a measuring mode. In addition, the execution of the test function can also be triggered manually by a user on the Coriolis mass flowmeter 1. The controller 5 is configured accordingly. If the test function has been executed multiple times, the controller adds the respective specific date to a list of stored historical data. In the event of an error, this list is then provided by the controller for error diagnosis.
[0050] In this exemplary embodiment, the value of the device parameter k stored in the controller 5 in the first method step 101 is determined by executing the test function. This execution of the test function ensures that a specific alignment of, on the one hand, the drive coil 6 and the drive coil core 7 relative to one another, and, on the other hand, the sensor coil 8 and the sensor coil core 9 relative to one another, is maintained, and that there is no damage to the drive electromagnet 3 or the sensor electromagnet 4. During the subsequent execution of the test function, a deviating alignment and / or damage are thus detected and displayed if the limit value is exceeded.
[0051] In an alternative embodiment, the value of the device parameter k stored in the controller 5 is determined from the design of the Coriolis mass flowmeter 1. Reference numeral
[0052] 1 Coriolis mass flowmeter
[0053] 2 measuring tube
[0054] 3 drive electromagnet
[0055] 4 Sensor electromagnet
[0056] 5 Control
[0057] 6 drive coil
[0058] 7 Drive coil core
[0059] 8 Sensor coil
[0060] 9 Sensor coil core
[0061] 10 Longitudinal axis
[0062] 11 camps
[0063] 12 Medium k Device parameters
[0064] U A Measuring drive voltage
[0065] IA measuring drive current
[0066] U T Test drive voltage
[0067] I T Test drive current
[0068] U s Measuring sensor voltage
[0069] Z Drive electromagnetic impedance
Claims
Patent claims 1. A method for testing a Coriolis mass flowmeter (1) with a measuring tube (2), at least one drive electromagnet (3), at least one sensor electromagnet (4), and a controller (5), wherein the at least one drive electromagnet (3) has a drive coil (6) and a drive coil core (7), wherein the at least one sensor electromagnet (4) has a sensor coil (8) and a sensor coil core (9), wherein the controller (5) is configured to excite a measuring oscillation of the measuring tube (2) by generating and feeding a measuring drive signal into the at least one drive coil (6) and to determine a mass flow of a medium (12) through the measuring tube (2) using an electrical measuring sensor signal of the at least one sensor coil (8) caused by the measuring oscillation, characterized in that a value of a device parameter (k) is stored in the controller (5),wherein the device parameter (k) is a quotient of a drive voltage and a sensor voltage, wherein the drive voltage is induced by the drive coil core (7) into the drive coil (6) of the at least one drive electromagnet (3) and the sensor voltage is induced by the sensor coil core (9) into the sensor coil (8) of the at least one sensor electromagnet (4), and wherein the induced drive voltage and the induced sensor voltage are produced by an oscillation of the measuring tube (2), and that the controller (5) executes a test function with the following steps: - generating and feeding into the at least one drive coil a test drive signal with a test drive frequency different from the natural frequencies of the measuring tube (2), - Measuring a test drive voltage (U T ) across the at least one drive coil (6) and a test drive current (I T ) by the at least one drive coil (6), - Determining a drive electromagnetic impedance (Z) using the test drive voltage (U T ) and the test drive current (I T ), - generating and feeding into the at least one drive coil (6) of the measuring drive signal, - Measuring a measuring drive voltage (U A ) across the at least one drive coil (6), a measuring drive current (I A ) by the at least one drive coil (6) and determining a measuring sensor voltage (U s ) above the at least one sensor coil (8), - Determining a value of the device parameter (k) using the drive electromagnetic impedance (Z), the measuring drive voltage (U A ), the measuring drive current (I A ) and the measuring sensor voltage (U s) and that an error is signaled by the controller (5) if a deviation of the determined value of the device parameter (k) from the stored value of the device parameter (k) is greater than a limit value stored in the controller (5).
2. Method according to claim 1, characterized in that the device parameter (k) is determined using the formula that the measuring drive voltage (U A ) is equal to a sum of a product of the drive electromagnetic impedance (Z) and the measuring drive current (I A ) and on the other hand a product of the device parameter (k) and the measuring sensor voltage (Us).
3. Method according to claim 1 or 2, characterized in that the stored value of the device parameter (k) is determined by the controller (5) by executing the test function, or that the stored value of the device parameter (k) is derived from simulated properties of the Coriolis mass flowmeter (1).
4. Method according to one of claims 1 to 3, characterized in that the test drive signal and the measurement drive signal are generated and fed in simultaneously.
5. Method according to one of claims 1 to 4, characterized in that the measuring drive signal has a natural frequency of the measuring tube (2).
6. Method according to one of claims 1 to 5, characterized in that a mass flow of a medium (12) through the measuring tube (2) of the control (5) using the measuring drive voltage (U A ) and the measuring sensor voltage (U s ) is determined.
7. Method according to one of claims 1 to 6, characterized in that the test function is carried out periodically during operation of the Coriolis mass flow meter (1) and / or is carried out when the Coriolis mass flow meter (1) changes to a measuring mode, and / or is carried out when the Coriolis mass flow meter (1) is started.
8. Method according to one of claims 1 to 7, characterized in that execution of the test function is triggered manually by a user.
9. Method according to one of claims 1 to 8, wherein the Coriolis mass flowmeter (1) has two sensor electromagnets (4), characterized in that the measuring sensor voltage (U s) is determined by measuring a first measuring voltage across the sensor coil (8) of one of the two sensor electromagnets (4) and a second measuring voltage across the sensor coil (8) of the other of the two sensor electromagnets (4) and then measuring the measuring sensor voltage (U s ) is determined as an average value of the first measuring voltage and the second measuring voltage.
10. Method according to one of claims 1 to 9, characterized in that the controller (5) stores the determined value of the device parameter (k) in a datum and that preferably a time stamp and / or meta data is / are additionally stored in the datum and the datum is provided for diagnosing the error.
11. The method according to claim 10, characterized in that the metadata comprise a temperature and / or a mass flow.
12. Method according to claim 10 or 11, characterized in that the data from the controller (5) is added to a list of stored historical data and the list is provided for diagnosing the error.