阅读说明：本技术 操作磁感应流量计的方法和磁感应流量计 (Method for operating a magneto-inductive flow meter and magneto-inductive flow meter ) 是由 迈克尔·林纳特 西蒙·玛利亚格 于 2018-11-14 设计创作，主要内容包括：本发明涉及一种操作磁感应流量计(1)的方法,并且涉及这种流量计,其中,在具有恒定磁场的恒定阶段(K)期间,确定原始测量电压的多个原始测量值(RM(t)),其中,原始测量电压(R)由流量相关分量(D)、干扰分量(S)和噪声分量(N)组成,其中每个原始测量值(RM(t))分别被分配流量测量值和干扰电压值,其中使用来自先前的第一恒定阶段的原始测量值和来自跟随第一恒定阶段的第二恒定阶段的原始测量值来计算干扰分量的第二干扰电压值和第二流量测量值,其中借助于第二流量测量值和所计算的第二干扰电压值的知识来校正来自第一恒定阶段和/或第二恒定阶段的第一流量测量值。(The invention relates to a method of operating a magnetically inductive flow meter (1), and to such a flow meter, wherein a plurality of raw measured values (RM (t)) of a raw measured voltage are determined during a constant phase (K) with a constant magnetic field, wherein the raw measurement voltage (R) is composed of a flow-dependent component (D), an interference component (S) and a noise component (N), wherein each raw measurement value (RM (t)) is assigned a flow measurement value and a disturbance voltage value, wherein a second interference voltage value and a second flow measurement value of the interference component are calculated using the raw measurement values from a preceding first constant phase and the raw measurement values from a second constant phase following the first constant phase, wherein the first flow rate measurement value from the first and/or second constant phase is corrected by means of the second flow rate measurement value and knowledge of the calculated second interference voltage value.)

1. A method for operating a magnetic inductive flow meter (1) for measuring a volume flow or a flow rate of a medium flowing through a measuring tube (10) of the flow meter,

a magnet system (20) applies a magnetic field perpendicular to the measuring tube axis to the medium in the measuring tube,

the magnetic field profile comprises a constant phase (K) with a constant magnetic field over time and an alternating phase (W) with a variable magnetic field over time,

the alternating phase is configured to change from a first constant phase with a first magnetic field to a subsequent second constant phase with a second magnetic field,

the second magnetic field is different from the first magnetic field;

tapping a flow-dependent electrical raw measurement voltage (R) induced in the medium by means of at least one measurement electrode pair (30), the measurement electrode pair (30) comprising a first measurement electrode (31) and a second measurement electrode (32);

an electronic measuring/operating circuit (77.7), which electronic measuring/operating circuit (77.7) evaluates the raw measuring voltage and determines a flow measurement value and is electrically connected to the measuring electrode,

characterized in that during each constant phase a plurality of raw measured values (RM (t)) of the raw measured voltage are determined, the raw measured voltage (R) consisting of a flow-dependent component (D), a disturbance component (S) and a noise component (N),

calculating a first flow measurement value (D1) and a first disturbance voltage value (S1) from each of the raw measurement values,

calculating a second interference voltage value and a second flow measurement value of the interference component (S) using a previous first constant phase raw measurement value and a second constant phase raw measurement value following the first constant phase,

the first flow rate measured value of the first and/or second constant phase is adapted by means of the second flow rate measured value and the knowledge of the calculated second interference voltage value.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein a subsequent expected value of the flow (PD1(t + dt)) is predicted on the basis of the first flow measurement value (D1(t)) and a subsequent expected value of the disturbance component (PS1(t + dt)) is predicted on the basis of the first disturbance voltage value (S1(t)),

another raw measurement (RM (t + dt)),

calculating a first flow rate measurement value (D1(t + dt)) by means of the expected value of the flow rate (PD1(t + dt)) and the further raw measurement value (RM (t + dt)), and calculating a first disturbance voltage value (S1(t + dt)) by means of the expected value of the disturbance voltage (PS1(t + dt)) and the further raw measurement value (RM (t + dt)),

the process is repeated to determine another first flow measurement (D1) and another first disturbance voltage value (S1).

3. The method of claim 2, wherein the first and second light sources are selected from the group consisting of,

wherein the expected value of the flow (PD1(t + dt)) and the expected value of the disturbance voltage and the weighting of the raw measured value (RM (t + dt)) are flow-dependent.

4. The method according to claim 2 or 3,

the prediction of the expected values of the flow rate and the interference voltage is based, for example, on a linear or a second-order continuity, or in particular on a taylor expansion.

5. The method of any one of claims 2 to 4,

wherein a first variance (V1) is assigned to an expected value of the flow (PD1(t + dt)),

and assigning a second variance (V2) to an expected value of the disturbance voltage (PS1(t + dt)),

and a third variance (V3) is assigned to the raw measurement (RM (t + dt)),

when calculating the first flow measurement value (D1) or the first disturbance voltage value (S1), the respective expected and raw measurement values are weighted based on the associated variance.

6. The method of claim 5, wherein the first and second light sources are selected from the group consisting of,

wherein the estimation of the variance (V1, V2, V3) is based on a difference or signal-to-noise ratio between the respective expected value (PD1(t + dt), PS1(t + dt)) and the raw measurement value (PM (t + dt)).

7. The method of any one of claims 2 to 6,

wherein a Kalman filter is used in the calculation of the expected value (PD1(t + dt), PS1(t + dt)) and the first flow measurement value (D1(t + dt)) and the first disturbance voltage value (S1(t + dt)).

8. The method of any one of claims 2 to 7,

wherein the occurrence of at least one of the following criteria suggests an alternating phase:

the first variance exceeds a first threshold;

the second variance exceeds a second threshold; and

the third party difference exceeds a third threshold; and

the deviation of the expected disturbance component (PS (t + dt)) from the first disturbance value (S1) exceeds a fourth threshold value.

9. The method according to any one of the preceding claims,

wherein at least two flow-dependent electrical raw measurement voltages (R) induced in the medium are tapped,

the curves of the raw measured voltages are compared,

when the raw measured voltage profile is changed without a corresponding change in the respective at least one other raw measured voltage profile, the corresponding change in the measured voltage is interpreted as a disturbance,

in the case of a uniform raw measurement voltage profile, a change in the raw measurement voltage is interpreted as a change in the flow rate.

10. The method of claim 9, wherein the first and second light sources are selected from the group consisting of,

wherein the comparison of the raw measurement voltage is performed on the basis of the raw measurement voltage or a first or second flow measurement value and/or a first or second interference voltage value derived therefrom.

11. The method according to claim 9 or 10,

wherein a first comparison voltage (VG1) between the first measuring electrode (31) and ground and a second comparison voltage (VG2) between the second measuring electrode (32) and ground are tapped via ground (M),

the ground is for example a ground electrode (ME) or a pipe connected to said measuring tube or to a grounding plate,

and/or

The flow-dependent electrical raw measurement voltage (R) is tapped off by means of at least two measurement electrode pairs (30).

12. The method according to any one of the preceding claims,

wherein the constant phase comprises at least 2, and especially at least 10, and preferably at least 50 raw measurement values.

13. The method according to any one of the preceding claims,

wherein the raw measurement values are calculated by averaging a plurality of tapped raw measurement voltages, the average comprising at least 2, and in particular at least 5, and preferably at least 10, and/or not more than 100, and in particular not more than 50, and preferably not more than 20 tapped raw measurement voltages.

14. The method according to any one of the preceding claims,

wherein during the constant phase the magnetic field is generated at least partially by at least one residual magnetic magnet (22), during the alternating phase the residual magnetic field of which is changed, in particular its polarity is reversed, by means of a coil system (21) comprising at least one coil (21.1),

or, during the constant phase, the magnetic field is generated at least partially by at least one permanent magnet (23) or at least partially by a coil system (21) comprising at least one coil (21.1), and, during the alternating phase, the magnetic field is changed by means of changing a magnetic field component generated by the coil system,

alternatively, the magnetic field is generated by a coil system comprising at least one coil.

15. A magnetic induction flow meter (1) configured to perform the method according to any of the preceding claims, comprising:

a measuring tube (10) having a measuring tube axis (11), which measuring tube is configured to guide the medium;

a magnet system (20), the magnet system (20) being configured to generate a magnetic field perpendicular to the measurement tube axis;

at least one measuring electrode pair (30, 31, 32), the at least one measuring electrode pair (30, 31, 32) for tapping an electrical measuring voltage induced by the magnetic field;

an electronic measurement/operation circuit (77.7), the electronic measurement/operation circuit (77.7) being configured to operate the magnet system (20) and the measurement electrode (31, 32) and to perform the method according to any one of the preceding claims.

16. The electromagnetic induction flow meter of claim 15,

wherein the magnet system (20) comprises at least one coil system (21), the coil system (21) comprising at least one coil (21.1), the magnet system in particular comprising at least one residual magnet (22), or in particular comprising at least one permanent magnet (23).

17. An electromagnetic induction flow meter according to claim 15 or 16,

wherein the flow meter comprises a ground electrode (ME).

Technical Field

The invention relates to an energy-saving method of operating a magnetic induction flow meter for measuring a flow rate or a volume flow of a medium flowing through a measuring tube of the flow meter, and to such a flow meter.

Background

Magnetic inductive flow meters make use of the following facts: the magnetic field deflects charged particles perpendicular to the magnetic field, the charged particles having a velocity component perpendicular to the magnetic field, the direction of the deflection depending on the sign of the charge.

In the electrically conductive medium flowing through the measuring tube of the magneto-inductive flow meter, an electrical measuring voltage is induced by a magnetic field extending perpendicularly to the measuring tube axis and can be tapped off by means of measuring electrodes and evaluated for flow measurement.

Ideally, the voltage tapped by the measuring electrodes is proportional to the magnetic field strength and to the flow of the medium through the measuring tube. However, electrochemical effects, for example on the surface of the dielectric measuring electrode, cause interference potentials which change over time and distort the flow measurement.

This disadvantage is overcome, for example, by establishing a measurement phase during which the medium is subjected to a constant magnetic field over time, wherein the measurement phase is interrupted by an alternating phase which is established for the alternating magnetic field strength and optionally the direction of the earth magnetic field. By tapping the measurement voltages from the different measurement phases and forming a difference, the influence of the interference potential and thus the corrected flow measurement value can be determined. As a result, a changing magnetic field must be determined for each flow measurement and each interference voltage.

Another procedure for determining and correcting the interference voltage is disclosed, for example, in WO 2015043746 a1, the technical background of which is an energy-saving magnetic induction flow meter with a low switching frequency. The first magnetic field having the first magnetic field strength is used to establish a second magnetic field having the second magnetic field strength and an immediately subsequent third magnetic field having the third magnetic field strength, wherein precisely one measured value of the measurement voltage is determined in each of the first and second magnetic fields, the other two measured values of the measurement voltage are determined in the third magnetic field, and a flow measurement corrected by means of a specific interference voltage is not obtained until the fourth measurement voltage.

The disadvantage of this solution is the long period during the two first magnetic fields, during which no flow measurement is performed.

Disclosure of Invention

It is therefore an object of the present invention to propose a method of operating a magnetic inductive flow meter and a magnetic inductive flow meter such that the energy required to operate the flow meter is small and more measurement time is available.

This object is achieved by a method according to independent claim 1 and by a magnetic induction flow meter according to independent claim 14.

In the method according to the invention for operating a magnetic inductive flow meter for measuring the volume flow or the flow rate of a medium flowing through a measuring tube of the flow meter,

a magnet system applies a magnetic field perpendicular to the measuring tube axis to the medium in the measuring tube,

the magnetic field profile comprises a constant phase K with a constant magnetic field over time, and an alternating phase W with a variable magnetic field over time,

the alternating phase is configured to change from a first constant phase with a first magnetic field to a subsequent second constant phase with a second magnetic field,

the second magnetic field is different from the first magnetic field;

measuring a flow-dependent electrical raw measurement voltage r (t) induced in the medium by means of at least one measuring electrode pair comprising a first measuring electrode and a second measuring electrode;

an electronic measuring/operating circuit, which is electrically connected to the measuring electrode, which evaluates the raw measuring voltage and determines a flow measurement value,

wherein

Determining a plurality of raw measured values RM (t) of a raw measured voltage during each constant phase, the raw measured voltage R consisting of a flow-dependent component D, an interference component S and a noise component,

calculating a first flow measurement value D1 and a first disturbance voltage value S1 from each raw measurement value RM (t),

a second disturbance voltage value Sb and a second flow rate measured value of the disturbance component S are calculated using the raw measured values of the previous first constant phase and the raw measured values of the second constant phase following the first constant phase,

the first flow rate measured value of the first and/or second constant phase is adapted by means of the second flow rate measured value and the knowledge of the calculated second interference voltage value.

The adaptation can be performed, for example, by means of a mathematical model.

By detecting a plurality of raw measurement voltages during a constant phase and calculating a plurality of first flow measurement values, while occasionally adapting or correcting by means of second flow measurement values, the frequency of change from a constant phase to a subsequent constant phase, and therefore the associated change in the magnetic field, may be small. The respective constant phase may thus comprise a duration of at least 0.5 seconds, or in particular at least 2 seconds or preferably at least 10 seconds. A typical duration of the alternating phase is less than 25 milliseconds. This results in a particularly advantageous ratio of the duration of the constant phase to the duration of the alternating phase of at least 20.

The terms "first constant phase" and "second constant phase" mean any two constant phases following each other.

In one embodiment of the method, a subsequent expected value of the flow rate is predicted based on the first flow measurement value, and a subsequent expected value of the disturbance component is predicted based on the first disturbance voltage value,

another raw measurement value is measured and,

calculating a first measured flow value by means of the expected value of the flow and by means of a further raw measured value, and calculating a first disturbance voltage value by means of the expected value of the disturbance voltage and by means of the further raw measured value,

the process is repeated to determine another first flow measurement and another first disturbance voltage value.

By calculating the next flow value or disturbance voltage value starting from the respective previous value by means of the expected flow value or disturbance voltage value and the raw measured value, the flow rate can be determined with the required accuracy with less calculation effort. This is an important aspect, in particular for field devices used in measurement and automation technology, and thus also for magnetic-inductive flow meters.

The expected value of the predicted flow is based on the determination of the rate of change. In addition to the rate of change, a higher time derivative may be determined, which may be used to calculate other subsequent expected values.

The predicted expectation value may also be based on a linear or a second-order continuity, or in particular on a taylor expansion.

In one embodiment of the method, the expected values of the flow and the disturbance voltage and the weighting of the raw measured values are flow-dependent.

For example, the uncertainty of the raw measurement values may be flow-dependent, in which case their weighting may be adapted.

In one embodiment of the method, the first party is assigned to an expected value of the traffic,

assigning a second variance to an expected value of the disturbance voltage,

and, a third party differential is assigned to the raw measurement,

in calculating the first flow measurement value or the first interference voltage value, the respective expected value and the raw measurement value are weighted based on the associated variance.

In one embodiment of the method, the estimation of the variance is based on the difference or signal-to-noise ratio between the corresponding expected value and the raw measured value.

In one embodiment of the method, kalman filtering is used during the calculation of the expected value and the calculation of the subsequent flow value and the subsequent interference voltage value.

The adaptation of the first flow measurement value to the second flow measurement value can be performed, for example, by varying a parameter of a kalman filter.

In an embodiment of the method, the alternating phase is initiated when at least one of the following criteria occurs:

the first variance exceeds a first threshold;

the second variance exceeds a second threshold; and

the third difference exceeds a third threshold; and

the deviation of the expected disturbance component from the disturbance voltage value exceeds a fourth threshold value.

Thus, the durations of the different constant phases may have different lengths and be adapted to the boundary conditions.

In one embodiment of the method, at least two flow-dependent electrical raw measurement voltages (R) induced in the medium are tapped,

the curves of the raw measured voltages are compared,

when the raw measured voltage profile is changed without a corresponding change in the respective at least one other raw measured voltage profile, the corresponding change in the measured voltage is interpreted as a disturbance,

in the case of a uniform raw measurement voltage profile, a change in the raw measurement voltage is interpreted as a change in the flow rate.

For example, when the voltage curves may be overlapped by multiplying the amplitude of the voltage curves by a constant factor and/or by offsetting one voltage curve by a constant value, there is agreement between the two voltage curves. For example, to detect the quality of the consistency, a correlation between two voltage curves may be determined.

In one embodiment of the method, the comparison of the raw measurement voltages is carried out on the basis of the raw measurement voltages or a first or second flow measurement value and/or a first or second interference voltage value derived therefrom.

In one embodiment of the method, a first comparison voltage between the first measuring electrode and ground and a second comparison voltage between the second measuring electrode and ground are tapped via ground,

the ground is for example a ground electrode or a pipe connected to a measuring pipe or a ground disc,

and/or

The flow-dependent electrical raw measurement voltage is tapped off by means of at least two measurement electrodes.

In this way, it can be identified whether the change in the tapped-off raw measurement voltage is due to a change in the flow or to a change in the interference voltage.

The different measuring electrode pairs can be arranged offset with respect to one another along the axis of the measuring tube or in cross section.

In one embodiment of the method, the constant phase comprises determining at least 2, and in particular at least 10, and preferably at least 50 raw measurement values. However, the constant phase may also comprise up to 1000000 raw measurement values.

In one embodiment of the method, the raw measurement values are calculated by averaging a plurality of tapped raw measurement voltages, wherein the average comprises at least 2, and in particular at least 5, and preferably at least 10, and not more than 100 and/or in particular not more than 50, and preferably not more than 20 tapped raw measurement voltages.

In the case of electronic measuring/operating circuits with low computing power, such averaging can reduce the burden without unduly limiting the accuracy of the measured voltage curve to be calculated.

In one embodiment of the method, during the constant phase, a magnetic field is generated at least partially by the at least one residual magnet,

during the alternating phase, the remanent magnetic field of the remanent magnet is changed, in particular its polarity is reversed,

or, during the constant phase, a magnetic field is generated at least partly by the at least one permanent magnet and at least partly by a coil system comprising at least one coil,

during the alternating phase, changing the magnetic field by means of changing the magnetic field component generated by the coil system;

alternatively, the magnetic field is generated by a coil system comprising at least one coil.

When at least one residual magnetic magnet is used, the energy required to operate the magnet system is limited to an occasional change in the residual magnetic field of the magnetic material, which means in particular a polarity reversal of the residual magnetic field. The change in the remanent magnetic field is caused by applying a sufficiently strong magnetic field pulse, for example a magnetic field pulse generated by means of a coil, to the remanent magnetic magnet. In case the constant phase is sufficiently long, energy can thereby be saved compared to a magnet system in which the magnetic field is generated only by the coil.

Alternatively, instead of at least one residual magnetic magnet, at least one permanent magnet may be used to at least partially generate the magnetic field. For example, the magnetic field of the permanent magnet may be modulated by adding a magnetic field generated by at least one coil. The alternating constant phases can be realized, for example, by switching on or off or by a general modulation of the magnetic field generated by the coil. In this case, the magnetic field generated by the coil is weak enough not to substantially affect the remanent magnetic field of the permanent magnet.

Therefore, whether the magnet is a permanent magnet or a remanent magnet is determined based on its use.

Therefore, a magnetic induction flow meter according to the invention configured to perform the method according to any of the preceding claims comprises:

a measurement tube having a measurement tube axis, the measurement tube configured to guide a medium;

a magnet system configured to generate a magnetic field perpendicular to the measurement tube axis;

at least one measuring electrode pair for tapping an electrical measuring voltage induced by the magnetic field;

electronic measurement/operation circuitry configured to operate the magnet system and the measurement electrode and to perform the method according to any of the preceding claims.

In one embodiment, the magnet system comprises at least one coil system with at least one coil, wherein the magnet system comprises in particular at least one residual magnetic magnet or in particular at least one permanent magnet.

In one embodiment, the flow meter includes a ground electrode.

Drawings

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

FIG. 1 shows an exemplary illustrative plot of a measured signal and a processed signal;

FIG. 2 shows a detail of the curve shown in FIG. 1 for describing the calculation steps of the method according to the invention;

FIG. 3 shows an exemplary plot of magnetic field and measured voltage curves over a plurality of constant phases;

fig. 4 shows an exemplary profile of the measured voltage development and of a first and a second comparative raw measured voltage by means of ground tapping;

fig. 5 shows an exemplary curve of two raw measurement voltages tapped by means of two measurement electrode pairs;

FIG. 6 illustrates an exemplary magnetic field profile; and

fig. 7 shows a magnetic induction flow meter.

Detailed Description

Fig. 1 shows an exemplary profile of a raw measurement voltage R in a medium during a constant phase with a constant magnetic field, which voltage is tapped off by means of a pair of measurement electrodes 30 of a magnetic induction measuring device 1, see fig. 6. The raw measurement voltage R is composed of a flow-dependent component D, an interference component S and signal noise N, wherein D is induced by the magnetic field acting on the measuring tube of the flowmeter and the flow rate of the medium in the medium. The interference component is generated by electrochemical processes occurring at the interface between the medium and the measuring electrodes 31, 32 (see fig. 6). The interference components exhibit a time-dynamic behavior which is significantly slower than the typical flow fluctuations occur, so that they can be separated from one another by signal processing measures. The curve of the raw measured voltage R is represented by an arbitrary raw measured voltage value rm (t), followed by a subsequent raw measured voltage value PM (t + dt). The measured voltage curve therefore comprises a flow-dependent component D which is not yet known and a disturbance component S which is not yet known. During the constant phase K, a first flow measurement value D1 and a first interference voltage value S1 are respectively assigned to the raw measurement voltage R during the constant phase K. By adding the first flow measurement value to the associated first interference voltage value, a measurement voltage profile VM can be calculated in which the signal noise N is at least partially suppressed.

Fig. 2 shows an exemplary enlarged detail of the curve shown in fig. 1, wherein, starting from any time t, the determination of the first flow measurement value D1 and the first interference voltage value S1 is shown immediately following.

Starting from the already calculated values D1 and S1 at any time t, the first flow measurement value and the corresponding value of the first disturbance voltage value are predicted for a subsequent time t + dt, so that an expected value of the flow PD1(t + dt) and an expected value of the disturbance voltage PS1(t + dt) result. The measured value RM (t + dt) of the raw voltage R at the time point t + dt is used to correct the expected value, wherein the uncertainty or variance of the expected value and the raw voltage measured value RM can be used to determine the weighting of the individual values during the correction, see enlarged details.

The expectation is based on a mathematical model, wherein the expectation of the flow is subject to a first variance V1, and wherein the expectation of the disturbance voltage is subject to a second variance V2, e.g. calculating the variance using the mathematical model, or estimating the variance. However, the variance may also be determined based on the flow rate of the medium, or it may be assumed that the variance is constant. Other criteria are for example the signal-to-noise ratio of the raw measured voltage. The raw measurement value RM (t + dt) measured at the time point t + dt has an uncertainty with a third-party difference V3. When the expected value PD1(t + dt) or PS1(t + dt) is calculated relative to the raw measured value RM (t + dt), the two values are weighted, for example, based on their variance. For example, the mathematical model may be based on a kalman filter. By calculating the expected value PD1 relative to the raw measurement value RM, a new first flow measurement value D1(t + dt) may be obtained for the point in time t + dt. Therefore, a new first disturbance voltage value S1(t + dt) is obtained by calculating the predicted value PS1 with respect to the raw measured value RM. By repeating the listed steps, it is thus possible to determine the development of the flow or of the flow-related component of the raw measurement voltage R and the development of the interference voltage during the constant phase.

If the deviation of the development measurement determined by the mathematical model from the disturbance value determined by the mathematical model exceeds a limit value, the magnet system can be prompted to switch from the current constant phase to the next phase.

Fig. 3 shows the change of the magnetic field B and the original voltage curve R over a plurality of constant phases K, during which the medium is subjected to a constant magnetic field, and alternating phases W, during which the magnetic field change takes place. The original voltage curve R follows the change in the magnetic field B, which is superimposed by the change in the flow and the change in the disturbance component. At the end of the constant phase and at the beginning of the subsequent constant phase, the corresponding raw voltage measurement rm (t) is used to determine a second verification flow measurement and a second verification interference voltage value, by means of which the mathematical model can be readjusted, by forming the difference between the two values.

Fig. 4 describes an advantageous embodiment of a method based on a measurement voltage curve and curves of a first comparison voltage VG1 and a second comparison voltage VG2, wherein the first comparison voltage is determined by determining a potential difference between the first measurement electrode 31 and ground, or in particular the ground electrode, and wherein the second comparison voltage is determined by determining a potential difference between ground or the ground electrode ME and the second measurement electrode 32.

If the two comparison voltages follow the same course, as shown at time t1, a change in the measured voltage is recognized as being caused by a change in the flow rate or a change in the interference voltage. If there is a significant deviation between the first and second comparison voltages, as shown at time t2, a change in the measurement voltage is interpreted as a change in the interference voltage.

Alternatively or additionally, as shown in fig. 5, it is also possible to tap the two raw measured voltages R1 and R2 by means of two measuring electrode pairs and to compare the curves of the two raw measured voltages. A consistent development of the two voltages, such as at time t1, may be interpreted as a flow change, while an inconsistent development may be interpreted as being caused by a disturbance. In this way, a distinction can be made between flow changes and interference effects, and additional information can be provided to the mathematical model. The principle can also be extended to three or more measuring electrode pairs.

The comparison of the voltages shown in fig. 4 and 5 can be performed on the basis of the measured raw measured voltage or the first or second flow rate measurement value and/or the first or second interference voltage value derived therefrom.

Fig. 6 shows a schematic curve of the magnetic field that can be generated using different magnet systems, wherein the upper curve can be produced, for example, by a magnet system comprising a coil system or by a magnet system comprising a coil system and at least one residual magnet.

For example, the coil system may generate a magnetic field that oscillates around a zero point. Such a magnetic field can also be generated, for example, by changing the remanence or by subjecting a remanent magnet to a magnetic pulse to reverse its polarity.

The magnetic field need not be symmetrical with respect to zero. The magnetic field profile shown in fig. 6 is provided by way of example and should not be construed as limiting.

The lower magnetic field curve shows the development in which a basic magnetic field is generated by the permanent magnet, wherein the total magnetic field results from the modulation of the basic magnetic field by means of the coil system.

In contrast to the curve shown in fig. 6, the duration of the successive constant phases may also be different. The duration of the curve shown in fig. 6 will be considered to be provided by way of example and not limitation.

Fig. 7 shows a schematic design of a magnetic induction flow meter 1, which magnetic induction flow meter 1 comprises a measuring tube 10 and a magnet system 20, which magnet system 20 comprises two coil systems 21, each comprising a coil 21.1 and two residual magnets 22 or permanent magnets 23, each residual magnet 22 or permanent magnet 23 being arranged in a coil system. The magnetic-inductive flow meter 1 further comprises a measuring electrode pair 30, which measuring electrode pair 30 comprises a first measuring electrode 31 and a second measuring electrode 32, with which the raw measuring voltage R can be tapped. In addition, the flow meter comprises a ground electrode, by means of which a first comparative raw measurement voltage VG1 between the first measurement electrode 31 and the ground electrode ME31 and a second comparative raw measurement voltage VG2 between the ground electrode and the second measurement electrode 32 can be tapped. The electronic measurement/operating circuit 77.7 of the flow meter is configured to operate the magnet system as well as the measuring electrodes and ground and to perform the method according to the invention.

List of reference numerals

1 magnetic induction flowmeter

10 measuring tube

20 magnet system

21 coil system

21.1 coil

22 remanence magnet

23 permanent magnet

30 measuring electrode pair

31 first measuring electrode

32 second measuring electrode

77.7 electronic measurement/operation circuit

Constant phase of K

W alternating phase

R original measurement voltage

RM (t) raw measurement value

D1 first flow measurement

Flow-dependent component of the raw measurement voltage

S interference component of original measurement voltage

S1 first interference voltage value

N noise component

VM measurement Voltage Curve

VM (t) Curve measurements

Prediction of PD1 flow

PS1 interference voltage anticipation

VS interference component curve

M ground

VG1 first comparison voltage

VG2 second comparison voltage

R1 first raw measurement voltage

R2 second raw measurement Voltage

ME ground electrode

First variance of V1

V2 second variance

V3 third party diff