Coriolis flow meter

Abstract

The invention relates to a Coriolis flow meter (1) for determining a time-varying process variable of a flowable medium, comprising a measuring tube (2) for conducting the medium, an excitation system for inducing a mechanical oscillation of the measuring tube (2), a sensor system (4) for detecting the mechanical oscillation of the measuring tube (2), the sensor system (4) is designed to generate at least a first sensor signal s1 and a second sensor signal s2, and a measurement and / or operation circuit (5), in particular formed by means of at least one microprocessor, the measurement and / or operation circuit (5) is designed to operate the excitation system with an excitation signal, the measurement and / or operation circuit (5) comprises an all-pass filter, the invention relates to a sensor device comprising an all-pass filter having a filter coefficient # imgabs0 # and designed to receive a first sensor signal s1 and to generate a filtered first sensor signal s1 *, a measurement and / or operation circuit (5) designed to receive the filtered first sensor signal s1 * and a second sensor signal s2, the measurement and / or operation circuit (5) comprising a control circuit (15), and a control unit which is designed to control a filter coefficient # imgabs1 # on the basis of the filtered first sensor signal s1 * and the second sensor signal s2 or on the basis of a variable derived from the filtered first sensor signal s1 * and the second sensor signal s2 in such a way that a control criterion is met, and the measuring and / or operating circuit (5) is designed to generate a first measured value representing the process variable as a function of the filter coefficient # imgabs2.

Description

Field of the Invention

[0001] The present invention relates to a Coriolis flowmeter for determining a time-varying process variable of a flowable medium. Background Art

[0002] Process measurement technology field devices having a vibrating type sensor, and in particular Coriolis flowmeters, have been known for many years. The basic structure of such a measuring device is described, for example, in EP1807681 A1, to which reference is made in its entirety in the context of the present invention regarding the structure of a general field device.

[0003] Generally, a Coriolis flowmeter has at least one or more vibrating measuring tubes, which can be set into vibration by a vibration exciter. These vibrations are transmitted along the tube length and vary depending on the type of the flowable medium located in the measuring tube and its flow velocity. At another point in the measuring tube, an oscillation sensor or in particular two oscillation sensors spaced apart from each other can record the changing oscillations in the form of a sensor signal or a plurality of sensor signals. Then, a measurement and / or operation circuit can determine the mass flow rate, viscosity, and / or density of the flowing medium based on the sensor signals.

[0004] To determine the mass flow rate, the following formula is generally used:

[0005]

[0006] is the drive frequency of the excitation signal, is the phase difference between two measured sensor signals, and is a calibration factor. Using this method, the mass flow rate for a stable flow velocity can be determined very accurately. The disadvantage is that under disturbed conditions - such as those in which a multiphase appears in the medium - and thus in the case of a time-unstable drive frequency and amplitude, the measurement system is no longer in a harmonic operating mode, and the above formula is no longer accurate enough or even invalid. In addition, a time offset may occur between the determined phase difference and the drive frequency i.e., the drive frequency assumed for the measured value of the process variable is not matched with the actual drive frequency present when measuring the sensor signal for determining the phase difference Summary of the Invention

[0007] Therefore, an object of the present invention is to solve this problem.

[0008] This object is achieved by a Coriolis flowmeter according to claim 1 and a Coriolis flowmeter according to the claim.

[0009] A Coriolis flowmeter for determining a time-varying process variable of a flowable medium according to the present invention includes:

[0010] - a measuring tube for conducting the medium;

[0011] - an excitation system for causing mechanical oscillations of the measuring tube;

[0012] - a sensor system for detecting the mechanical oscillations of the measuring tube,

[0013] wherein the sensor system is configured to generate at least a first sensor signal and a second sensor signal,

[0014] - a measuring and / or operating circuit, in particular formed by at least one microprocessor,

[0015] wherein the measuring and / or operating circuit is configured to operate the excitation system with an excitation signal,

[0016] wherein the measuring and / or operating circuit includes an adaptive filter, in particular an all-pass filter, having filter coefficients which is configured to receive the first sensor signal and generate a filtered first sensor signal,

[0017] wherein the measuring and / or operating circuit includes a control circuit which is configured to receive the filtered first sensor signal and the second sensor signal,

[0018] wherein the control circuit is configured to control the filter coefficients based on the filtered first sensor signal and the second sensor signal or variables derived from the filtered first sensor signal and the second sensor signal such that a control criterion is satisfied,

[0019] wherein the measuring and / or operating circuit is configured to generate a first measured value representing the process variable according to the filter coefficients This results in the first measured value representing the process variable (e.g., mass flow, viscosity, density) not being determined analytically anymore, but being derived from the two sensor signals and the filter coefficients determined by the control system

[0020] By controlling the all-pass filter via the filter coefficients, for example, such that the filtered first sensor signal matches the second sensor signal within tolerance limits, the information of the first measured value representing the process variable is projected onto the filter coefficients Thus, the filter coefficients ​​Describe the influence of the process variable to be determined on the sensor signal and thus be proportional thereto. If the first measured value representing the process variable is determined according to the filter coefficients not only is the measurement error reduced, but the drive frequency needs to be precisely synchronized in time with the phase difference . This prevents a dynamic zero offset from occurring in the case of strong frequency fluctuations.

[0021] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0022] One embodiment provides that the control circuit is configured to determine the filter coefficients by means of the least mean squares algorithm and / or the recursive least squares algorithm .

[0023] The control circuit is preferably located close to the sensor system such that the sensor signal only travels a short distance to the control circuit. Furthermore, the sensor signal is preferably provided to the control circuit immediately after generation such that there is no time delay that would occur if the sensor signal first had to pass through electronic components to form the phase difference.

[0024] One embodiment provides that the control circuit includes a PID controller that is configured to control the filter coefficients based on the filtered first sensor signal and the second sensor signal or a variable derived from the filtered first sensor signal and the second sensor signal such that a control criterion is met.

[0025] One embodiment provides that the process variable includes the mass flow rate of the medium.

[0026] One embodiment provides that the excitation signal has a drive frequency ,

[0027] wherein the drive frequency is not included in the determination of the first measured value representing the process variable of the medium - in particular the mass flow rate.

[0028] One embodiment provides that the control criterion includes that the deviation between the filtered first sensor signal and the second sensor signal presents a sensor signal setpoint or is less than a sensor signal limit value.

[0029] One embodiment provides that the measurement and / or operation circuit is configured to detect the phase difference between the filtered first sensor signal and the second sensor signal ,

[0030] wherein the derived quantity corresponds to the phase difference .

[0031] One embodiment provides that the control criterion includes a phase difference corresponding to a phase difference setpoint and / or being less than a phase difference limit.

[0032] One embodiment provides that, additionally, a calibration factor , in particular determined at the factory, is included in the generation of a first measured value representing a process variable, in particular a mass flow rate.

[0033] One embodiment provides that a measurement and / or operation circuit is designed to determine and optionally output a current process state from filter coefficients

[0034] One embodiment provides that the current process state includes the presence of gas bubbles in the medium.

[0035] One embodiment provides that the measurement and / or operation circuit is configured to:

[0036] - In a first operating mode, determine and output a second measured value representing a process variable based on a phase difference between a first sensor signal or a filtered first sensor signal and a second sensor signal and a driver frequency ;

[0037] - In a second operating mode, determine and output a first measured value representing a process variable based on filter coefficients .

[0038] One embodiment provides that the measurement and / or operation circuit is configured to switch from the first operating mode to the second operating mode when a deviation between the first measured value and the second measured value exhibits a setpoint and / or lies outside a tolerance range.

[0039] One embodiment provides that the measurement and / or operation circuit is configured to determine the presence of gas bubbles by comparing a first signal and a second signal.

[0040] One embodiment provides that the measurement and / or operation circuit is configured to:

[0041] - Determine a second measured value representing a process variable, in particular a mass flow rate, based on a phase difference between a filtered first sensor signal or a first sensor signal and a second sensor signal and a driver frequency ;

[0042] - Correct the second measured value based on filter coefficients or the first measured value, and

[0043] - Output the corrected second measured value.

[0044] ​One embodiment provides that an all-pass filter is designed such that the mathematical relationship between the first sensor signal and the filtered first sensor signal can be described via a transfer function having a Laplace exponent of .

[0045] A Coriolis flowmeter for determining a time-varying process variable of a flowable medium according to the present invention includes:

[0046] - A measuring tube for conducting the medium;

[0047] - An excitation system for causing mechanical oscillations of the measuring tube;

[0048] - A sensor system for detecting mechanical oscillations of the measuring tube,

[0049] wherein the sensor system is configured to generate at least a first sensor signal and a second sensor signal,

[0050] - A measuring and / or operating circuit, in particular formed by at least one microprocessor,

[0051] wherein the measuring and / or operating circuit is designed to operate the excitation system with an excitation signal,

[0052] wherein the measuring and / or operating circuit includes a first adaptive filter having filter coefficients , the first adaptive filter being configured to receive the first sensor signal and generate a filtered first sensor signal,

[0053] wherein the measuring and / or operating circuit (5) includes a second adaptive filter having filter coefficients , which is configured to receive the second sensor signal s2 and generate a filtered second sensor signal s2*,

[0054] wherein the measuring and / or operating circuit includes a control circuit configured to receive the filtered first sensor signal s1* and the filtered second sensor signal s2*, or variables derived from the filtered first sensor signal s1* and the filtered second sensor signal s2*,

[0055] wherein the control circuit is configured to control the filter coefficients and / or the filter coefficients based on the filtered first sensor signal s1* and the filtered second sensor signal s2*, or variables derived from the filtered first sensor signal s1* and the filtered second sensor signal s2*, such that a control criterion is satisfied,

[0056] wherein the measuring and / or operating circuit is configured to be based on the filter coefficients and / or from filter coefficients to generate a first measurement value representative of a process variable.

[0057] This results in the first measurement value representative of the process variable (e.g., mass flow, viscosity, density) no longer being analytically determined, but being derived from two sensor signals and filter coefficients and / or derived and / or determined by a control system. By controlling an adaptive first filter via filter coefficients and controlling an adaptive second filter via filter coefficients such that, for example, the filtered first sensor signal s1* matches the filtered second sensor signal s2* within tolerance limits, information of the first measurement value representative of the process variable is projected onto the filter coefficients and / or . The filter coefficients and / or the filter coefficients thus describe or describe the influence of the process variable to be determined on the sensor signals and are thus proportional thereto. If the first measurement value representative of the process variable is determined according to the filter coefficients and / or the filter coefficients , not only is the measurement error reduced, but the drive frequency has to be precisely synchronized in time with the phase difference . This prevents a dynamic zero offset from occurring in the case of strong frequency fluctuations.

[0058] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0059] One embodiment provides that the control circuit is configured to determine the filter coefficients and / or the filter coefficients by a least mean squares algorithm and / or by a normalized least mean squares algorithm and / or by a recursive least squares algorithm and / or a linear or non-linear gradient method.

[0060] The control circuit is preferably located close to the sensor system such that the sensor signals only travel a short distance to the control circuit. Furthermore, the sensor signals are preferably provided to the control circuit immediately after generation such that there is no time delay that would occur if the sensor signals first had to pass through electronic components to form a phase difference.

[0061] One embodiment provides that the control circuit includes a PID controller configured to control the filter coefficients and / or filter coefficients such that a control criterion is met.

[0062] One embodiment provides that the process variable includes the mass flow rate of the medium.

[0063] One embodiment provides that the excitation signal has a driver frequency ,

[0064] wherein the driver frequency is not included in the determination of the first measurement value representing the mass flow rate of the medium.

[0065] One embodiment provides that the control criterion includes that the deviation between the filtered first sensor signal s1* and the filtered second sensor signal s2* exhibits a sensor signal setpoint or is less than a sensor signal limit value.

[0066] One embodiment provides that the measurement and / or operation circuit is configured to detect the phase difference between the filtered first sensor signal s1* and the filtered second sensor signal s2* ,

[0067] wherein the derived variable corresponds to the phase difference .

[0068] One embodiment provides that the control criterion includes the phase difference corresponding to a phase difference setpoint and / or being less than a phase difference limit.

[0069] One embodiment provides that, additionally, a calibration factor , in particular determined at the factory, is included in the generation of the first measurement value representing the process variable, in particular the mass flow rate.

[0070] One embodiment provides that the measurement and / or operation circuit is configured to and / or from filter coefficients determine and optionally output the current process state.

[0071] One embodiment provides that the current process state includes the presence of bubbles in the medium.

[0072] One embodiment provides that the measurement and / or operation circuit is configured to:

[0073] - in a first operating mode, determine and output a second measurement value representing the process variable based on the first sensor signal or the phase difference between the filtered first sensor signal s1* and the filtered second sensor signal s2* and the driver frequency and output it.

[0074] - In the second operating mode, a first measured value representing a process variable is determined and output based on filter coefficients and / or filter coefficients A first measured value representing a process variable is determined and output

[0075] One embodiment provides that the measuring and / or operating circuit is configured to switch from the first operating mode to the second operating mode when the deviation between the first measured value and the second measured value presents a setpoint and / or lies outside a tolerance range

[0076] One embodiment provides that the measuring and / or operating circuit is configured to determine the presence of bubbles by comparing a signal representing the first measured value and a signal representing the second measured value

[0077] One embodiment provides that the measuring and / or operating circuit is configured to

[0078] - Determine a second measured value representing a process variable, in particular a mass flow rate, based on the phase difference between the filtered first sensor signal s1* or the first sensor signal and the filtered second sensor signal s2* or the second sensor signal s2 and the drive frequency - Correct the second measured value based on filter coefficients

[0079] and / or filter coefficients or the first measured value, and

[0080] - Output the corrected second measured value

[0081] One embodiment provides that the first filter is designed such that the mathematical relationship between the first sensor signal and the filtered first sensor signal can be described by a transfer function having a Laplace exponent with a Laplace exponent One embodiment provides that the first filter is designed such that the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be described by a transfer function having a Laplace exponent

[0082] with a Laplace exponent One embodiment provides that the first filter is designed such that the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be described by a transfer function

[0083] One embodiment provides that the first filter is designed such that the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be described by a transfer function

[0084] where is the z-variable of a discrete system

[0085] One embodiment provides that the second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function having a Laplace exponent and .

[0086] One embodiment provides that the second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function .

[0087] wherein is the z variable of a discrete system.

[0088] One embodiment provides that the second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* is described via a transfer function .

[0089] wherein is the z variable of a discrete system.

[0090] One embodiment provides that the second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function .

[0091] One embodiment provides that must be satisfied.

[0092] One embodiment provides a first adaptive filter and / or a second adaptive filter, in particular each being an all-pass filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The present invention will be explained in more detail with reference to the following drawings, in which:

[0094] Figure 1 shows a diagram of a Coriolis volumetric flowmeter according to the prior art;

[0095] Figure 2 shows diagrams of two embodiments of a Coriolis flowmeter according to the present invention; and

[0096] Figure 3 shows another diagram of two embodiments of a Coriolis flowmeter according to the present invention. DETAILED DESCRIPTION

[0097] Figure 1Shows a schematic diagram of a Coriolis flowmeter 1 according to the prior art. The Coriolis flowmeter 1 for determining a time-varying process variable of a flowable medium includes a measuring tube 2 for guiding the medium. A straight measuring tube 3 is clearly shown. However, the use of curved and / or multiple measuring tubes is known. The core idea of the present invention can be applied to measuring tubes of any shape and number.

[0098] An excitation system 3 for causing mechanical oscillations of the measuring tube 2 interacts with the measuring tube 2. One or more excitation coils per measuring tube are suitable for this purpose, which are arranged in the housing of the Coriolis flowmeter or in a specially designed arrangement within the housing by means of holding devices on the measuring tube. The excitation coils usually interact with magnets arranged directly on the measuring tube or arranged on the measuring tube via holding devices. However, other excitation systems are also known. Therefore, the excitation system can also be in mechanical contact with the measuring tube 2 and is designed and configured to transfer its own oscillation behavior to the measuring tube 2. However, the nature of the excitation system 3 is not essential for the present invention.

[0099] The Coriolis flowmeter 1 further includes a sensor system 4 for detecting the mechanical oscillations of the measuring tube 2. The sensor system 4 usually includes two sensor coils per measuring tube, and each sensor coil interacts with a magnet arranged on the measuring tube 2. The sensor coils can be arranged in the housing (not shown) of the Coriolis flowmeter 1 by means of holding devices on the measuring tube 2 like the excitation coils, or arranged in an arrangement (not shown) provided inside the housing for this purpose. The sensor coils are usually arranged offset from each other in the flow direction of the medium. The excitation coil is arranged between the two sensor coils in the flow direction of the medium. However, different sensor systems are also known. The mechanical oscillations of the measuring tube 2 can also be detected using optical sensors. The nature of the sensor system 4 is not essential for the present invention. The sensor system 4 is configured to generate at least a first sensor signal s1 and a second sensor signal s2, where the first sensor signal s1 and the second sensor signal s2 describe the current oscillation behavior of the measuring tube 2 at two different position offsets along the flow direction.

[0100] In the illustrated embodiment, the sensor system 4 includes two sensor coils, and the excitation system includes one excitation coil. The positioning of the two sensor coils and the excitation coil is chosen for a clearer representation of the figure and does not correspond to the actually necessary arrangement. The first sensor signal s1 is provided to one of the two sensor coils, and the second sensor signal s2 is provided to the corresponding other sensor coil.

[0101] The excitation system 3 and the sensor system 4 are connected to a measurement and / or operation circuit 5, which particularly includes at least one microprocessor and electronic components (e.g., including transistors, resistors, capacitors, mixers, filters, and / or microcontrollers). In the illustrated embodiment, the measurement and / or operation circuit 5 includes a control unit 6, which is configured to provide an excitation signal having a drive frequency and an excitation amplitude , and thus operate the excitation system. In the illustrated embodiment, the excitation signal can be described as , where the excitation amplitude is the maximum excitation coil current and the time-dependent current excitation coil current. The drive frequency and the excitation amplitude are adjustable variables. The control unit 6 is designed to supply the excitation amplitude to the mixer 16 and - in the form of - supply the time-varying (periodic) part of the excitation signal. The mixer 16 creates the excitation signal from the two parts and forwards it to the excitation system 3. In addition, the control unit 6 is electrically connected to four other mixers 9a - d. The control unit 6 is designed to supply signals at the mixers 9a, 9c and supply signals at the mixers 9b, 9c. In addition, the control unit 6 is configured to transmit the current drive frequency to the calculation unit 8. The calculation unit 8 is also part of the measurement and / or operation circuit 5 and is configured to determine the mass flow at least based on the supplied drive frequency . The drive frequency is output or included in the determination of further process variables.

[0102] can be described by the first sensor signal s1. is the first phase, and is the first signal amplitude. The first sensor signal s1 is transmitted to particularly the multiplier mixers 9a, 9b for frequency conversion. The mixer 9a is configured to apply a sine component to the first sensor signal s1. For example, the mixer 9a can be configured to multiply the first sensor signal s1 by the sine function . The mixer 9b is configured to apply a cosine component to the first sensor signal s1. Thus, the mixer 9b can be configured to multiply the first sensor signal s1 by the cosine function 。The results of the two mixers 9a, 9b are provided to the filters 10a, 10b in each case. The filters 10a, 10b can for example be low-pass filters. These can be configured to eliminate the 2f component of the sensor signal. Furthermore, the filters 10a, 10b are configured to limit the bandwidth of the incoming sensor signal in order to reduce the noise component. The filtered results are provided to the computing unit 11a, which is suitable and configured to execute an algorithm. The algorithm can for example be an iterative algorithm, in particular a coordinate rotation digital computer algorithm, with which mathematical functions can be executed. The algorithm is designed and configured to determine the first phase and the first signal amplitude 。The first signal amplitude can be output or used to determine another process variable.

[0103] can be described by the second sensor signal s2. is the second phase, and is the second signal amplitude. In the flowing medium, the second phase is offset from the first phase by the phase difference 。The second sensor signal s2 is transmitted to the multiplier mixers 9c, 9d in particular. Mixer 9c is configured to apply a sine component to the second sensor signal s2. For example, mixer 9a can be configured to multiply the second sensor signal s2 by the sine function 。Mixer 9b is configured to apply a cosine component to the second sensor signal s2. Thus, mixer 9b can be configured to multiply the second sensor signal s2 by the cosine function 。The results of the two mixers 9c, 9d are provided to the filter 10 in each case. The filters 10c, 10d can for example be low-pass filters. The filtered results are provided to the computing unit 11b, which is configured to execute an algorithm. The algorithm can for example be an iterative algorithm, in particular a coordinate rotation digital computer algorithm, with which mathematical functions can be executed. The algorithm is designed and configured to determine the second phase and the second signal amplitude 。The second signal amplitude can be output or used to determine another process variable. The first phase and the second phase are each provided to the filters 12a, 12b. The filters 12a, 12b are configured to reduce the respective noise components of the determined phases. The filters 12a, 12b can for example be low-pass filters.

[0104] The measurement and / or operation circuit 15 also has a subtractor 13. The first phase and the second phase is input into a subtracter 13. The subtracter 13 is configured to determine the phase difference proportional to the mass flow rate between the first phase and the second phase and provide it to a calculation unit 8. The calculation unit 8 is configured to determine the mass flow rate based on the phase difference and the provided driver frequency . Based on the equation the mass flow rate is determined . Determine the mass flow rate .

[0105] Figure 2 FIG. shows diagrams of two Coriolis flow meters according to the invention. The first embodiment is shown by the dashed line and the second embodiment is shown by the solid line.

[0106] According to the first embodiment, a first sensor signal s1 is provided to an all-pass filter 7. The all-pass filter 7 is a signal processing filter that equally passes all frequencies but changes the phase relationship between different frequencies. The all-pass filter 7 is configured to receive the first sensor signal s1 and generate a filtered first sensor signal s1*. The transfer function for converting the first sensor signal s1 into the filtered first sensor signal s1* must satisfy . is the Laplace exponent.

[0107] The measurement and / or operation circuit 5 has a control circuit 15, which is configured to control the filter coefficients based on the filtered first sensor signal s1* and the second sensor signal s2 or variables derived from the filtered first sensor signal s1* and the second sensor signal s2 such that a control criterion is satisfied. The control criterion can be the deviation between the filtered first sensor signal s1* and the second sensor signal s2, which must take on a sensor signal setpoint or must be less than a sensor signal limit value. According to the invention, the control circuit 15 can be configured to determine the filter coefficients by a least mean squares algorithm and / or a recursive least squares algorithm. Alternatively, the control circuit 15 can include a PID controller, which is configured to control the filter coefficients based on the filtered first sensor signal s1* and the second sensor signal s2 or variables derived from the filtered first sensor signal s1* and the second sensor signal s2 such that a control criterion is satisfied.

[0108] The measurement and / or operation circuit 5 includes a calculation unit 14, which is configured to derive from the filter coefficients A first measurement value representing a process variable is generated. Additionally, in particular, a calibration factor determined in the factory is included in the generation of the first measurement value representing the process variable, in particular the mass flow rate. The equation . Therefore, the drive frequency is not included in the determination of the first measurement value representing the process variable (in particular the mass flow rate).

[0109] Alternatively or additionally, the measurement and / or operation circuit 5, in particular the computing unit 14, may be configured to determine and optionally output the current process state from the filter coefficients . An example of the process state to be detected is the presence of bubbles in the medium.

[0110] In a second embodiment, the measurement and / or operation circuit 5 is configured to determine the phase difference between the filtered first sensor signal s1* and the second sensor signal s2 . For this purpose, the first sensor signal s1 is provided to an all-pass filter where it is filtered. The filtered sensor signal s*1 passes through mixers 9a, 9b where it is mixed as described for the prior art. After mixing, the filtered first sensor signal s*1 to which the sine component is applied passes through filter 10a. Filter 10a is designed to eliminate the 2f component of the mixed sensor signal s*1 and reduce the noise component.

[0111] Then it is provided to the computing unit 11a which is set to calculate the first signal amplitude of the filtered first sensor signal . The filtered first sensor signal s*1 to which the cosine component is applied passes through filter 10b. Like filter 10a, filter 10b is configured to eliminate the 2f component of the mixed sensor signal s*1 and reduce the noise component. Then it is provided to the computing unit 11b which is configured to process the filtered first phase of the filtered first sensor signal . The filtered first phase is further passed through filter 12a before being provided to the subtractor 13.

[0112] To determine the phase difference , the second sensor signal s2 passes through mixers 9c, 9d, filters 10c, 10d, computing unit 11b, and filter 12b. The processing of the second sensor signal s2 corresponds to the processing described in the drawing description. The determined second phase is provided to the subtractor. The subtractor 13 is configured to determine the phase difference between the filtered first phase and the second phase , and provide it to the controller unit 15. The controller unit 15 is configured to control the filter coefficients such that the phase difference corresponds to the phase difference setpoint and / or is less than the phase difference limit. In particular, control the filter coefficients such that the phase difference is minimum or zero. Similarly as in the previous embodiment, the calculation unit 14 is configured to determine a measured value representing the process variable based on the filter coefficients and the calibration factor .

[0113] The third embodiment combines the processes of two previous embodiments and groups them into different operating modes. In the first operating mode, a second measured value representing the process variable is determined, and optionally output based on the phase difference between the first sensor signal s1 or the filtered first sensor signal s1* and the second sensor signal s2 and the drive frequency. The second measured value can be the mass flow rate. In the second operating mode, the first measured value representing the process variable is determined based on the filter coefficients and optionally output. The measurement and / or operation circuit 5 is configured to switch from the first operating mode to the second operating mode when the deviation between the first measured value and the second measured value presents a setpoint and / or lies outside the tolerance range. The second measured value can be corrected based on the filter coefficients or the first measured value, and the corrected second measured value can be output.

[0114] Figure 3 Shows another schematic diagram of two Coriolis flow meters according to the present invention. The third embodiment is shown by a dashed line, and the fourth embodiment is shown by a solid line.

[0115] According to the third embodiment, the first sensor signal s1 is provided to the first adaptive filter 7a. The first filter 7a can be an all-pass filter. An all-pass filter is a signal processing filter that allows all frequencies to pass equally but changes the phase relationship between different frequencies. The first filter 7a is configured to receive the first sensor signal s1 and generate the filtered first sensor signal s1*. The transfer function for converting the first sensor signal s1 into the filtered first sensor signal s1* must satisfy . is the Laplace exponent.

[0116] Alternatively, the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can also be expressed via a transfer function with the Laplace exponent .

[0117] Alternatively, the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be expressed via the transfer function . In this case, is the z variable of the discrete system.

[0118] According to the first embodiment, the second sensor signal s2 is provided to the second adaptive filter 7b. The second filter 7b can also be an all-pass filter. An all-pass filter is a signal processing filter that allows all frequencies to pass equally but changes the phase relationship between different frequencies. The second filter 7b is configured to receive the second sensor signal s2 and generate a filtered second sensor signal s2*. The transfer function by which the second sensor signal s2 is converted into the filtered second sensor signal s2* must satisfy . is also the Laplace exponent.

[0119] Alternatively, the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be expressed via the transfer function . In this case, is the z variable of the discrete system.

[0120] Alternatively, the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be expressed via the transfer function . In this case, is the z variable of the discrete system.

[0121] Alternatively, the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be expressed via the transfer function .

[0122] The measurement and / or operation circuit 5 has a control circuit 15 that is configured to control the filter coefficients and / or the filter coefficients based on the filtered first sensor signal s1* and the filtered second sensor signal s2* or variables derived from the filtered first sensor signal s1* and the filtered second sensor signal s2* such that a control criterion is satisfied. The control criterion can be the deviation between the filtered first sensor signal s1* and the filtered second sensor signal s2*, which must assume a sensor signal setpoint or must be less than a sensor signal limit value. According to the invention, the control circuit 15 can be configured to determine the filter coefficients by the least mean squares algorithm and / or by the normalized least mean squares algorithm and / or by the recursive least squares algorithm and / or linear or non-linear gradient methods and / or filter coefficients .

[0123] Alternatively, the control circuit 15 may include a PID controller configured to control the filter coefficients based on the filtered first sensor signal s1* and the filtered second sensor signal s2* or a variable derived from the filtered first sensor signal s1* and the filtered second sensor signal s2* and / or filter coefficients such that a control criterion is met.

[0124] The measurement and / or operation circuit 5 includes a computing unit 14 configured to derive an initial measurement of the current mass flow through the pipeline from the filter coefficients and / or filter coefficients Additionally, a calibration factor is included in the determination of the first measurement value representing the mass flow rate, which calibration factor is determined in particular at the factory. The equation or or must be satisfied. Thus, the drive frequency is not included in the determination of the first measurement value representing the mass flow rate of the medium.

[0125] Alternatively or additionally, the measurement and / or operation circuit 5, in particular the computing unit 14, may be configured to determine the current process state from the filter coefficients and / or from the filter coefficients and optionally output it. An example of a process state to be detected is the presence of bubbles in the medium.

[0126] In a fourth embodiment, the measurement and / or operation circuit 5 is configured to determine the phase difference between the filtered first sensor signal s1* and the filtered second sensor signal s2* For this purpose, the first sensor signal s1 is provided to an adaptive first filter where it is filtered. The filtered sensor signal s*1 passes through mixers 9a, 9b where it is mixed as described for the prior art. After mixing, the filtered first sensor signal s*1 with the sine component passes through a filter 10a. The filter 10a is designed to eliminate the 2f component of the mixed sensor signal s*1 and reduce the noise component.

[0127] It is then provided to a computing unit 11a which is set up to calculate the first signal amplitude of the filtered first sensor signal 。The filtered first sensor signal s*1 applying the cosine component passes through filter 10b. Like filter 10a, filter 10b is configured to eliminate the 2f component of the mixed sensor signal s*1 and reduce the noise component. Then it is provided to calculation unit 11b, which is configured to process the filtered first phase of the filtered first sensor signal 。The filtered first phase further passes through filter 12a before being provided to subtractor 13.

[0128] To determine the phase difference ,the second sensor signal s2 is provided to adaptive second filter 7b, where it is filtered. The filtered sensor signal s*1 passes through mixers 9c, 9d, filters 10c, 10d, calculation unit 11b, and filter 12b. The processing of the filtered second sensor signal s2* corresponds to the processing described in the accompanying drawing description. The determined second phase is provided to the subtractor. Subtractor 13 is configured to determine the filtered first phase and the second phase between the phase differences ,and provides it to controller unit 15. Controller unit 15 is configured to control the filter coefficients ,such that the phase difference corresponds to the phase difference setpoint and / or is less than the phase difference limit. In particular, control the filter coefficients and / or the filter coefficients ,such that the phase difference is minimized or zero. Similarly as in the previous embodiment, calculation unit 14 is configured to determine a measured value representing the mass flow rate according to the filter coefficients and / or the filter coefficients and the calibration factor .

[0129] The third embodiment combines the processes of two previous embodiments and groups them into different operating modes. In the first operating mode, a second measured value representing the process variable is determined and optionally output according to the phase difference between the first sensor signal s1 or the filtered first sensor signal s1* and the second sensor signal s2 or the filtered second sensor signal s2* and the driver frequency and / or the filter coefficients is output. The measurement and / or operation circuit 5 is configured to switch from a first operating mode to a second operating mode when the deviation between the first measurement value and the second measurement value presents a setpoint and / or lies outside a tolerance range. The second measurement value can be adjusted according to the filter coefficient and / or the filter coefficient or the first measurement value, and the corrected second measurement value is output.

[0130] List of reference symbols

[0131] 1 Coriolis flowmeter

[0132] 2 Measuring tube

[0133] 3 Excitation system

[0134] 4 Sensor system

[0135] 5 Measurement and / or operation circuit

[0136] 6 Control unit

[0137] 7 All-pass filter

[0138] 8 Calculation unit

[0139] 9 i Mixer

[0140] 10 i Filter

[0141] 11 i Calculation unit

[0142] 12 i Filter

[0143] 13 Subtractor

[0144] 14 Calculation unit

[0145] 15 Control circuit

[0146] 16 Mixer

Claims

1. A Coriolis flowmeter (1) for determining a time-varying process variable of a flowable medium, comprising: - Measuring tube (2) for conducting the medium; - Excitation system (3) for causing mechanical oscillations of the measuring tube (2); - Sensor system (4) for detecting the mechanical oscillations of the measuring tube (2), wherein the sensor system (4) is configured to generate at least a first sensor signal s1 and a second sensor signal s2, - Measuring and / or operating circuit (5), in particular formed by means of at least one microprocessor, wherein the measuring and / or operating circuit (5) is configured to operate the excitation system with an excitation signal, wherein the measurement and / or operation circuit (5) comprises an adaptive filter, in particular an all-pass filter, having filter coefficients and is configured to receive the first sensor signal s1 and to generate a filtered first sensor signal s1*. wherein the measuring and / or operating circuit (5) includes a control circuit (15) configured to receive the filtered first sensor signal s1* and the second sensor signal s2 or a variable derived from the filtered first sensor signal s1* and the second sensor signal s2, Wherein, the control circuit (15) is configured to control the filter coefficients based on the filtered first sensor signal s1* and the second sensor signal s2 or a variable derived from the filtered first sensor signal s1* and the second sensor signal s2 such that a control criterion is met wherein the measurement and / or manipulation circuit (5) is configured to generate a first measured value representative of the process variable in accordance with the filter coefficients ​ 2. The Coriolis flowmeter according to claim 1, wherein, The control circuit (15) is configured to adjust the filter coefficients using a least mean square algorithm and / or a recursive least squares algorithm .

3. The Coriolis flowmeter according to claim 1, wherein, The control circuit (15) includes a PID controller configured to control the filter coefficients based on the filtered first sensor signal s1* and the second sensor signal s2 or a variable derived from the filtered first sensor signal s1* and the second sensor signal s2 such that the control criterion is satisfied.

4. The Coriolis flowmeter according to any one of the preceding claims, wherein, The control criterion includes that the deviation between the filtered first sensor signal s1* and the second sensor signal s2 presents a sensor signal setpoint or is less than a sensor signal limit value.

5. The Coriolis flowmeter according to any one of the preceding claims, wherein, The measurement and / or operation circuit (5) is configured to detect a phase difference between the filtered first sensor signal s1* and the second sensor signal s2 , wherein, the derived quantity corresponds to the phase difference .

6. The Coriolis flowmeter according to any one of the preceding claims, wherein, The measurement and / or operation circuit (5) is configured to determine a current process state based on the filter coefficients and optionally output it.

7. The Coriolis flowmeter according to any one of claims 4 to 6, wherein, The measuring and / or operating circuit (5) is configured to: - In a first operating mode, a second measured value representing the process variable is determined and output based on the phase difference between the first sensor signal s1 or the filtered first sensor signal s1* and the second sensor signal s2 and the drive frequency ​ - In a second operating mode, a first measured value representative of the process variable is determined and output based on the filter coefficients ​ 8. The Coriolis flowmeter according to claim 7, wherein, wherein, The measuring and / or operating circuit (5) is configured to switch from the first operating mode to the second operating mode when the deviation between the first measurement value and the second measurement value presents a setpoint and / or is outside the tolerance range.

9. The Coriolis flowmeter according to claim 8, wherein, wherein, The measuring and / or operating circuit (5) is configured to determine the presence of bubbles by comparing the first signal and the second signal.

10. The Coriolis flowmeter according to any one of the preceding claims, wherein, The measuring and / or operating circuit (5) is configured to: - based on the filtered first sensor signal s1* or the phase difference between the first sensor signal s1 and the second sensor signal s2 and the drive frequency to determine a second measured value representing the process variable, in particular the mass flow - Correct the second measurement value according to the filter coefficient or the first measurement value, and - Output a corrected second measurement value.

11. A Coriolis flowmeter (1) for determining a time-varying process variable of a flowable medium, comprising: - Measuring tube (2) for conducting the medium; - Excitation system (3) for causing mechanical oscillations of the measuring tube (2); - Sensor system (4) for detecting the mechanical oscillations of the measuring tube (2), wherein the sensor system (4) is configured to generate at least a first sensor signal s1 and a second sensor signal s2, - Measuring and / or operating circuit (5), in particular formed by means of at least one microprocessor, wherein the measuring and / or operating circuit (5) is configured to operate the excitation system with an excitation signal, wherein the measurement and / or operation circuit (5) comprises a first adaptive filter (7a) having filter coefficients configured to receive the first sensor signal s1 and generate a filtered first sensor signal s1*, wherein the measurement and / or operation circuit (5) comprises a second adaptive filter (7b) having filter coefficients configured to receive the second sensor signal s2 and generate a filtered second sensor signal s2*, wherein the measuring and / or operating circuit (5) includes a control circuit (15) configured to receive the filtered first sensor signal s1* and the filtered second sensor signal s2* or a variable derived from the filtered first sensor signal s1* and the filtered second sensor signal s2*, Wherein, the control circuit (15) is configured to control the filter coefficients based on the filtered first sensor signal s1* and the filtered second sensor signal s2* or variables derived from the filtered first sensor signal s1* and the filtered second sensor signal s2* and / or the filter coefficients such that a control criterion is satisfied wherein the measurement and / or operation circuit (5) is configured to generate a first measured value representative of the process variable in accordance with the filter coefficient and / or in accordance with the filter coefficient ​ 12. The Coriolis flowmeter according to claim 11, wherein, The control circuit (15) is configured to determine the filter coefficients by a least mean square algorithm and / or by a normalized least mean square algorithm and / or by a recursive least squares algorithm and / or by a linear or non-linear gradient method and / or the filter coefficients .

13. The Coriolis flowmeter according to claim 11, wherein, wherein, The control circuit (15) includes a PID controller configured to control the filter coefficients based on the filtered first sensor signal s1* and the filtered second sensor signal s2*, or variables derived from the filtered first sensor signal s1* and the filtered second sensor signal s2* and / or the filter coefficients such that the control criteria are met.

14. The Coriolis flowmeter according to any one of the preceding claims, wherein, The process variable includes the mass flow rate of the medium.

15. The Coriolis flowmeter according to claim 14, wherein, wherein, The excitation signal has a driver frequency, wherein the driver frequency is not included in the determination of the first measurement value representing the mass flow rate of the medium.

16. The Coriolis flowmeter according to any one of claims 11 to 15, wherein, The control criterion includes that the deviation between the filtered first sensor signal s1* and the filtered second sensor signal s2* exhibits a sensor signal setpoint or is less than a sensor signal limit value.

17. The Coriolis flowmeter according to any one of the preceding claims, wherein, The measurement and / or operation circuit (5) is configured to determine the phase difference between the filtered first sensor signal s1* and the filtered second sensor signal s2* , Among them, the derived variable corresponds to the phase difference .

18. The Coriolis flowmeter according to claim 5 or 13, wherein, The control criteria include the phase difference corresponding to a phase difference setpoint and / or less than a phase difference limit.

19. The Coriolis flowmeter according to any one of the preceding claims, wherein, Additionally, the calibration factor , in particular the factory-determined calibration factor is included in the generation of the first measured value representing the process variable, in particular the mass flow.

20. The Coriolis flowmeter according to any one of the preceding claims, wherein, The measurement and / or operation circuit (5) is configured to determine and optionally output the current process state as a function of the filter coefficients and / or as a function of the filter coefficients ​ 21. The Coriolis flowmeter according to claim 5 or 20, wherein, The current process state includes the presence of bubbles in the medium.

22. The Coriolis flowmeter according to any one of the preceding claims, wherein, The measuring and / or operating circuit (5) is configured to: - In a first operating mode, a second measured value representing the process variable is determined and output based on a phase difference between the first sensor signal s1 or the filtered first sensor signal s1* and the filtered second sensor signal s2*, and the driver frequency ​ - In the second operating mode, the first measured value representing the process variable is determined and output based on the filter coefficient and / or the filter coefficient ​ 23. The Coriolis flowmeter according to claim 7, wherein, wherein, The measuring and / or operating circuit (5) is configured to switch from the first operating mode to the second operating mode when the deviation between the first measured value and the second measured value exhibits a setpoint and / or lies outside a tolerance range.

24. The Coriolis flowmeter according to claim 22, wherein, wherein, The measuring and / or operating circuit (5) is configured to determine the presence of bubbles by comparing a signal representing the first measured value and a signal representing the second measured value.

25. The Coriolis flowmeter according to any one of claims 11 to 24, wherein, The measuring and / or operating circuit (5) is configured to: - based on the phase difference between the filtered first sensor signal s1* or the first sensor signal s1 and the filtered second sensor signal s2* or the second sensor signal s2 and the drive frequency to determine the second measured value representing the process variable, in particular the mass flow rate - according to the filter coefficients and / or to correct the second measurement value according to the first measurement value, and - output a corrected second measured value.

26. The Coriolis flowmeter according to any one of the preceding claims, wherein, The first filter is designed such that the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be described via a transfer function with a Laplace exponent .

27. The Coriolis flowmeter according to any one of claims 1 to 25, wherein, wherein, The first filter is designed such that the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be described via a transfer function with a Laplace exponent .

28. The Coriolis flowmeter according to any one of claims 1 to 25, wherein, wherein, The first filter is designed such that the mathematical relationship between the first sensor signal s1 and the filtered first sensor signal s1* can be described via a transfer function to be described, Among them, is the z variable of the discrete system.

29. The Coriolis flowmeter according to any one of claims 11 to 28, wherein, The second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function having a Laplace exponent thereof .

30. The Coriolis flowmeter according to any one of claims 11 to 28, wherein, The second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function to be described. Among them, is the z variable of the discrete system.

31. The Coriolis flowmeter according to any one of claims 11 to 28, wherein,The second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function to be described, Among them, is the z variable of the discrete system.

32. A Coriolis flowmeter according to any one of claims 11 to 28, wherein, The second filter is designed such that the mathematical relationship between the second sensor signal s2 and the filtered second sensor signal s2* can be described via a transfer function to be described.

33. A Coriolis flowmeter according to any one of the preceding claims, wherein, Must be satisfied .

34. A Coriolis flowmeter according to any one of the preceding claims, wherein, The first adaptive filter and / or the second adaptive filter are each in particular all-pass filters.

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