DE102020114515A1 - Electromagnetic flow measuring device - Google Patents

Abstract

The invention relates to a magnetic-inductive flow measuring device for determining a measured variable that is dependent on the flow rate, comprising:
- A device (5) for generating a magnetic field, the device (5) for generating the magnetic field comprising a primary coil (6) and an operating circuit (7) for applying an operating signal (11) to the primary coil (6);
- A device (8) for tapping a measuring voltage induced in the flowable medium,
- A device (9) for detecting a test variable, the test variable depending at least on the magnetic field and / or on a change in the magnetic field over time;
- A regulator circuit (10) for regulating the operating signal (11) as a function of the determined test variable, the regulator circuit (10) being set up to regulate at least one operating signal parameter of the operating signal (11) so that a measured value of the test variable does not differ from a predetermined one Setpoint deviates.

Description

The invention relates to a magneto-inductive flow measuring device for determining a measured variable that is dependent on the flow rate.

Electromagnetic flow measuring devices are used to determine the flow rate and the volume flow of a flowing medium in a pipeline. A distinction is made between inline magnetic-inductive flowmeters and magnetic-inductive flow measurement probes, which are inserted into a side opening of a pipeline. An electromagnetic flowmeter has a magnet system that generates a magnetic field perpendicular to the direction of flow of the flowing medium. Individual coils are usually used for this. In order to achieve a predominantly homogeneous magnetic field, pole pieces are additionally shaped and attached in such a way that the magnetic field lines run essentially perpendicular to the transverse axis or parallel to the vertical axis of the measuring tube over the entire pipe cross-section. In addition, an electromagnetic flowmeter has a measuring tube on which the device for generating the magnetic field is arranged. A pair of measuring electrodes attached to the outer surface of the measuring tube picks up an electrical measuring voltage or potential difference that is applied perpendicular to the direction of flow and to the magnetic field, which occurs when a conductive medium flows in the direction of flow when a magnetic field is applied. Since the measured voltage, according to Faraday's law of induction, depends on the speed of the flowing medium, the flow rate and - with the addition of a known pipe cross section - the volume flow can be determined from the induced measurement voltage.

In contrast to a magnetic-inductive flow measuring device, which comprises a measuring tube for guiding the medium with an attached device for generating a magnetic field penetrating the measuring tube and measuring electrodes, magnetic-inductive flow measuring probes with their usually circular cylindrical housing are inserted into a lateral opening of a pipeline and fixed in a fluid-tight manner . A special measuring tube is no longer necessary. The above-mentioned measuring electrode arrangement and coil arrangement on the outer surface of the measuring tube are omitted and are replaced by a device for generating a magnetic field arranged inside the housing and in close proximity to the measuring electrodes, which is designed so that an axis of symmetry of the magnetic field lines of the generated magnetic field The front surface or the surface between the measuring electrodes intersects vertically. In the state of the art there are already a large number of different magneto-inductive flow measuring probes.

Magnetic-inductive flow measuring devices are widely used in process and automation technology for fluids with an electrical conductivity of around 5 µS / cm. Corresponding flow measuring devices are sold by the applicant in a wide variety of embodiments for different areas of application, for example under the name PROMAG or MAGPHANT.

There are a number of different methods for regulating the operating signal impressed on the coil arrangement. As a rule, the aim of these is to generate a magnetic field with a magnetic induction that is as constant as possible over the entire measurement phase. For example, in the WO 2014/001026 A1 teaches a control in which a voltage signal applied to the coil arrangement is regulated in such a way that a coil current flowing through the coil arrangement reaches and maintains a coil current setpoint in a specified measurement phase. The coil current flowing through the coil arrangement generates a magnetic field with a magnetic induction that is dependent on the coil current. It is fundamentally assumed that by setting up a fixed coil current setpoint, the magnetic induction of the generated magnetic field also assumes a setpoint in a reproducible manner. The advantage of such a control system is that the control system manages without measuring the magnetic induction. However, it has been found that - due to temperature changes and magnetic interference fields - the magnetic induction cannot be reproduced solely by regulating it to a fixed coil current setpoint. As a result, the value for the magnetic induction assumed for the determination of the flow velocity-dependent measured variable deviates from the currently present magnetic induction in the medium. Depending on the disturbance variable, this can lead to deviations of up to 20% when determining the measured variable that is dependent on the flow rate.

The invention is based on the object of remedying the problem.

The object is achieved by the magnetic-inductive flow measuring device according to claim 1.

• - eine Vorrichtung zum Erzeugen eines Magnetfeldes,

wobei die Vorrichtung zum Erzeugen des Magnetfeldes eine Primärspule und eine Betriebsschaltung zum Anlegen eines Betriebssignales an die Primärspule umfasst;

• - eine Vorrichtung zum Abgreifen einer im fließfähigen Medium induzierten Messspannung,
• - eine Vorrichtung zum Erfassen einer Prüfgröße,

wobei die Prüfgröße zumindest von dem Magnetfeld und/oder von einer zeitlichen Veränderung des Magnetfeldes abhängt;

• - eine Reglerschaltung zum Regeln des Betriebssignales in Abhängigkeit der ermittelten Prüfgröße,

wobei die Reglerschaltung dazu eingerichtet ist, mindestens einen Betriebssignalparameter des Betriebssignales so zu regeln, dass ein Messwert der Prüfgröße nicht von einem vorgegebenen Sollwert abweicht.The magnetic-inductive flow measuring device according to the invention for determining a measured variable that is dependent on the flow rate comprises:

• - a device for generating a magnetic field,

wherein the device for generating the magnetic field comprises a primary coil and an operating circuit for applying an operating signal to the primary coil;

• - a device for tapping a measuring voltage induced in the flowable medium,
• - a device for detecting a test variable,

wherein the test variable depends at least on the magnetic field and / or on a change in the magnetic field over time;

• - a regulator circuit for regulating the operating signal as a function of the test variable determined,

wherein the regulator circuit is set up to regulate at least one operating signal parameter of the operating signal in such a way that a measured value of the test variable does not deviate from a predetermined target value.

Controlling the operating signal parameter as a function of the test variable has the technical effect that the magnetic field or magnetic induction in the measuring tube or in the pipeline can be reproduced more precisely.

In particular when an external interference field is present, the magnetic induction in the flowing medium no longer depends exclusively on the coil current. By regulating the at least one operating signal parameter as a function of the test variable, external interference fields are recognized and this is taken into account when generating the magnetic field, so that the resulting magnetic induction in the medium also assumes the specified target value with the interference field. Furthermore, temperature influences on the device for generating the magnetic field, which have an effect in particular on the magnetic properties - such as the permeability number - of individual field-conducting components, can also be compensated in the primary coil by the control according to the invention.

The device for tapping the measuring voltage induced in the flowable medium comprises, for example, two preferably diametrically arranged measuring electrodes which are set up to form a galvanic contact with the medium to be conveyed. Magnetic-inductive flow measuring devices with more than two measuring electrodes are also known. Alternatively, the device for tapping the measuring voltage induced in the flowable medium can comprise two measuring electrodes that do not come into contact with the medium.

The device for detecting the test variable comprises, for example, a Hall sensor and / or a secondary coil arrangement which comprises at least one secondary coil. A Hall sensor is designed to measure the magnetic field directly, whereas the secondary coil is suitable for detecting a voltage induced by the change in the magnetic field and thus also dependent on it.

Advantageous refinements of the invention are the subject matter of the subclaims.

One embodiment provides that the operating signal comprises a voltage with a time-variable course which is divided into time intervals,
wherein a sign of an applied voltage changes in successive time intervals,
wherein the time intervals each comprise a first time sub-interval,
wherein in a time interval the profile comprises a first voltage, in particular preferably constant over the entire duration of the first time sub-interval, which is applied to the primary coil during the first time sub-interval,
induced measurement voltages, which are determined in the first time sub-interval, are used to determine the measured variable that is dependent on the flow rate.

The operating signal comprises a voltage with a temporally alternating sign in order to suppress signal noise and / or a zero point or voltage offset. However, when the polarity of the voltage applied to the device for generating the magnetic field changes in polarity, this results in disruptive effects which mean that after each polarity change, a certain amount of time must be waited for the magnetic field to reach its local end state. This period is known as the settling phase. The period in which the magnetic field has settled and is essentially constant is referred to as the measurement phase, since the induced measurement voltage or a variable that is dependent on the induced measurement voltage is measured in the medium during this period.

One embodiment provides that the time intervals each include a second time sub-interval,
wherein a second voltage, which is constant over the entire duration of the second time sub-interval and is applied to the primary coil during the second time sub-interval, is applied to the voltage profile in a time interval,
where the second voltage is greater than the first voltage,
where in the voltage curve the first time sub-interval follows the second time sub-interval,
wherein a duration of the second time sub-interval is less than a duration of the first time sub-interval.

It has proven to be advantageous to significantly reduce the duration of the settling phase emphasized to apply a second voltage (= overvoltage) for a duration of a second time sub-interval to the device for generating the magnetic field. The second voltage is greater than the first voltage. This has the technical effect that the duration of the polarity reversal process, in which the magnetic field changes over time, is reduced.

One embodiment provides that the at least one operating signal parameter comprises the first voltage, the second voltage, a duration of the time interval, a duration of the first time sub-interval, a duration of the second time interval and / or a control variable dependent on the first voltage and the second voltage.

It has been found to be advantageous to set up the control circuit to regulate the duration of the second time sub-interval and the first voltage and accordingly to set a fixed value for the duration of the first time sub-interval and / or the second voltage.

One embodiment provides that the regulator circuit is set up to regulate the first voltage of a time interval as a function of the measured value of the test variable detected, in particular in the immediately preceding time interval, so that the deviation of the measured value of the test variable from the target value becomes smaller or a value assumes a predetermined tolerance range.

The first tension will be - different than in the WO 2014/001026 A1 learned - not regulated in such a way that the coil current assumes a constant coil current setpoint during the measurement phase. Such a regulation is not flexible enough to react to external disturbance magnetic fields or temperature influences. According to the invention, instead of the coil current flowing through the coil, a measured value of the test variable is taken into account and the first voltage is varied in such a way that the test variable assumes a setpoint value in the measurement phase. The coil current remains variable and can be varied depending on the magnetic field actually present.

One embodiment provides that the duration of the second time sub-interval is a variable and controllable variable.

This has the technical effect that the duration of the settling of the coil current and thus also of the magnetic field generated thereby can be adapted after the second time sub-interval and a measurement error caused by the settling is reduced.

One embodiment provides that the device for detecting the test variable comprises a secondary coil,
wherein the test variable comprises a voltage induced in the secondary coil and / or a variable that is dependent on the induced voltage.

The use of a secondary coil to record the test variable has proven to be particularly advantageous compared to Hall sensors. On the one hand, a secondary coil is less sensitive to temperature changes than common Hall sensors. On the other hand, temperature influences are reflected in the electrical resistance of the secondary coil and can thus be corrected, for example, by determining the coil current at the primary coil.

One embodiment provides that the device for generating the penetrating magnetic field comprises a coil core,
wherein the primary coil and the secondary coil each have a receptacle,
wherein the coil core extends through the receptacle of the secondary coil and the primary coil.

In order to determine the magnetic field present in the medium and the associated magnetic induction as precisely as possible, it is advisable to arrange the secondary coil as close as possible to the center of the measuring tube or pipeline. For example, it would be advisable to arrange the secondary coil between the insulating liner and the carrier tube or between the carrier tube and the pole piece. However, it has surprisingly been found to be particularly advantageous to arrange the secondary coil and the primary coil around a common coil core. As a result, changes in the magnetic field over time - for example caused by the primary coil - can be detected and recorded, as a result of which readjustment of the operating signal parameters can be initiated significantly earlier.

One embodiment provides that the duration of the second time interval is regulated in such a way that a determined value of a variable dependent on the test variable assumes a setpoint value within the duration of the second time interval.

This refinement is particularly advantageous when the first voltage is also regulated. This has the technical effect of correcting sudden changes in the existing magnetic field, which occur, for example, when an external magnet is attached to the magnetic-inductive flow measuring device. The purpose of regulating the duration of the second time sub-interval is to ensure that the change in the magnetic field over time approaches zero as early as possible. A slow oscillation of the magnetic field - which in the worst case extends into the measurement phase - can thus be avoided.

The variable that is dependent on the test variable includes, for example, a time integral or a sum over the determined measured variables of the test variable.

One embodiment provides that the magneto-inductive flow measuring device is designed as a magneto-inductive flow measuring device, comprising a measuring tube for guiding a flowable medium.

One embodiment provides that the magneto-inductive flow measuring device is designed as a magneto-inductive flow measuring probe for insertion into a lateral opening of a pipeline, comprising a housing to which the medium is applied,
wherein the device for generating the magnetic field is arranged in the housing.

One embodiment provides that the second voltage assumes a constant value over the course.

• 1: einen Querschnitt durch eine Ausgestaltung eines erfindungsgemäßen magnetisch-induktiven Durchflussmessgerätes;
• 2: eine erste Ausgestaltung des Verlaufes der Spannung und dem entsprechenden erzeugten Magnetfeld durch die Primärspule;
• 3: eine zweite Ausgestaltung des Verlaufes der Spannung und dem entsprechenden erzeugten Magnetfeld durch die Primärspule; und
• 4: eine perspektivische Ansicht auf eine teilweise geschnittene Ausgestaltung einer erfindungsgemäßen magnetisch-induktiven Durchflussmesssonde.

The invention is explained in more detail with reference to the following figures. It shows:

• 1 : a cross section through an embodiment of a magnetic-inductive flow measuring device according to the invention;
• 2 : a first embodiment of the course of the voltage and the corresponding generated magnetic field through the primary coil;
• 3 : a second embodiment of the course of the voltage and the corresponding generated magnetic field through the primary coil; and
• 4th : a perspective view of a partially sectioned embodiment of a magnetic-inductive flow measuring probe according to the invention.

the 1 shows a cross section of an embodiment of the magnetic-inductive flow measuring device according to the invention 1 . The structure and the measuring principle of an electromagnetic flowmeter 1 are basically known. Through a measuring tube 2 a medium is passed which has an electrical conductivity. The measuring tube 2 includes a support tube 3 , which is usually made of steel, ceramic, plastic or glass. One device 5 for generating a magnetic field is attached in such a way that the magnetic field lines are oriented essentially perpendicular to a longitudinal direction defined by the measuring tube axis. The device 5 for generating the magnetic field comprises a saddle coil or a primary coil 6. Through a receptacle 15th the primary coil 6th extends a coil core 14. As a recording 15th is the one through which the primary coil 6th forming coil wire to understand limited volume. The recording 15th the primary coil 6th can thus be formed by a coil holder or by the imaginary enclosed volume. The latter occurs when the coil wire of the primary coil 6th right around the coil core 14th is wrapped. The coil core 14th is formed from a magnetically conductive, in particular soft magnetic material. The device 5 for generating the magnetic field comprises a pole piece 21 that is at one end of the coil core 14th is arranged. The pole piece 21 can be a separate component or monolithic with the coil core 14th be connected. In the illustrated embodiment of the 1 have two primary coils 6th , 6.2 each have a coil core 14th , 14.2 and a pole piece 21 , 21.2 on. The two coil cores 14th , 14.2 are via a field return 22nd connected with each other. The field return 22nd connects the sides of the coil cores facing away from each other 14th , 14.2 with each other. The primary coil 6th is with an operating circuit 7th connected to which the primary coil 6th operates with an operating signal. The operating signal can be a voltage with a time-varying course. That through the device 5 A magnetic field built up to generate the magnetic field is generated by means of an operating circuit 7th Generated pulsed direct current of alternating polarity. This ensures a stable zero point and makes the measurement insensitive to the effects of electrochemical interference. The two primary coils 6th , 6.2 can separately with the operating circuit 7th connected or connected in series or parallel to each other.

When a magnetic field is applied, it arises in the measuring tube 2 a flow-dependent potential distribution, which can be recorded, for example, in the form of an induced measurement voltage. One device 8th to tap the induced measuring voltage is on the measuring tube 2 arranged. In the embodiment shown, the device is 8th for tapping the induced measuring voltage through two measuring electrodes arranged opposite one another 17th , 18th formed to form a galvanic contact with the medium. However, there are known from magnetic-inductive flowmeters that are attached to the outer wall of the support tube 3 As a rule, these are arranged diametrically and form an electrode axis or are cut by a transverse axis that is perpendicular to the magnetic field lines and the longitudinal axis of the measuring tube 2 runs. But there are also devices 8th known for tapping the induced measuring voltage, which have more than two measuring electrodes. The measured variable, which is dependent on the flow rate, can be determined on the basis of the measured voltage. The measured variable that is dependent on the flow rate includes the flow rate, the volume flow and / or the mass flow of the medium. One Measuring circuit 8th is set up to do this on the measuring electrodes 17th , 18th Detect applied, induced measuring voltage and an evaluation circuit 24 is designed to determine the measured variable that is dependent on the flow rate.

The carrier tube 3 is often formed from an electrically conductive material such as steel. To derive the at the first and second measuring electrode 2 , 3 applied measuring voltage via the carrier tube 3 To prevent this, the inner wall is lined with an insulating material, for example a (plastic) liner 4.

Commercially available magnetic-inductive flowmeters have, in addition to the measuring electrodes 17th , 18th two more electrodes 19th , 20th on. On the one hand, one is ideally used at the highest point in the measuring tube 2 attached level monitoring electrode 19th in addition, a partial filling of the measuring tube 1 to detect, and is set up to forward this information to the user and / or to take the fill level into account when determining the volume flow. A reference electrode is also used 20th , which are usually diametrically opposed to the level monitoring electrode 19th or at the lowest point of the measuring tube cross-section, to set a controlled, electrical potential in the medium. Usually the reference electrode 20th used to connect the flowing medium to an earth potential.

The embodiment according to the invention has a device 9 to record a test variable. The test variable depends at least on the magnetic field and / or a change in the magnetic field over time. Magnetic interference fields can also influence the test variable. The device 9 for detecting the test variable is as a secondary coil 13th with a recording 16 educated. The coil core 14th extends through the inclusion 16 of the secondary coil 13. In 1 the illustration shows two diametrically arranged secondary coils 13th , 13.2, through which one of the two coil cores 14th , 14.2 extends. The two secondary coils 13th , 13.2 can be used separately with the measuring circuit 23 connected, connected in series or parallel to each other. The measuring circuit 23 is set up to take measured values of the test variable by means of the device 9 to determine the test variable. According to the embodiment shown, the test variable is one in the secondary coil 13th induced voltage and / or a variable dependent on the induced voltage. The variable that is dependent on the induced voltage can be a sum or an integral of the measured values of the test variable over a specific period of time. The determined measured values of the test variable are taken into account for the regulation of the operating signal, in particular at least one operating signal parameter. The regulator circuit 10 is set up for the at least one operating signal parameter of the operating signal 11th to be changed in such a way that the measured value of the test variable does not deviate from a specified target value. The target value can be determined in an adjustment process and made available at the factory.

The operating circuit 7th , Regulator circuit 10 , Measuring circuit 23 and evaluation circuit 24 can be part of a single electronic circuit or form individual circuits.

the 2 shows a first embodiment of the operating signal and the corresponding magnetic field generated by the primary coil. According to the invention, the operating signal comprises a voltage with a time-variable course 12th , which is divided into time intervals t. The sign of the applied voltage changes in successive time intervals t. This in 2 operating mapped signal comprises t time intervals, each having a first time subinterval t _hold in which the entire duration of the first time interval part a constant first voltage U _hold to the primary coil _hold t is applied. The measured voltage, which is recorded for the determination of the measured variable as a function of the flow rate, is determined in the first time sub-interval t _hold . According to the first embodiment, the regulator circuit is set up _{to regulate the first voltage U hold of} a time interval t as a function of the measured value of the test variable detected in particular in the immediately preceding time interval so that the deviation of the measured value of the test variable from the target value becomes smaller or a value assumes from a specified tolerance range. According to the _{invention, the first voltage U hold} is a variable that can be regulated over time.

the 3 shows a second embodiment of the operating signal, the correspondingly generated magnetic field by the primary coil and the test variable which is dependent at least on the magnetic field and / or on a change in the magnetic field over time. According to the invention, the operating signal comprises a voltage with a time-variable course 12th , which is divided into time intervals t. The sign of the applied voltage changes in successive time intervals t. This in 3 operating mapped signal comprises t time intervals, each having a first time subinterval t _hold in which the entire duration of the first time interval part a constant first voltage U _hold to the primary coil _hold t is applied. The measured voltage, which is recorded for the determination of the measured variable as a function of the flow rate, is determined in the first time sub-interval t _hold . In addition, the time intervals t each have a second time sub-interval t _shot in which one, in particular over the entire duration of the second time sub-interval t _shot constant second voltage U _shot to the primary coil ( 6th ) is created. The second voltage U _{shot is} greater than the first voltage U _hold . In the course of the voltage, the first time sub-interval t _hold follows the second time sub-interval t _shot . In addition, the duration of the second time sub-interval t _{shot is shorter} than the duration of the first time sub-interval t _hold . The duration of the second time sub-interval t _shot is variable and controllable over time. Likewise the first voltage U _hold . The two voltages can be set so that a ratio between the first voltage U _hold and the second voltage U _shot over the entire course 12th is constant. This means that by regulating the first voltage U _hold , the second voltage U _shot is also automatically adapted proportionally to the change. Alternatively, the second voltage U _{shot can be used} over the entire course 12th assume a constant value. In addition to regulating the first voltage U _hold , the duration of the second time interval t _shot is regulated in such a way that a determined value of a variable dependent on the test variable assumes a target value _{within the duration of the second time interval t shot.} The variable that is dependent on the test variable can be, for example, a sum or an integral of the measured values of the test variable for a predetermined time segment. The test variable is a voltage induced on the secondary coil. During the second time sub-interval t _shot , the induced voltage rises abruptly and then decreases continuously as long as the second voltage U _{shot is applied} to the primary coil. When the first voltage U _hold is applied, the induced voltage drops to zero. The course of an integral over the course of the measured values of the test variable over time essentially corresponds to the course of the depicted course over time of the magnetic field generated or present in the measuring tube.

The in 3 The courses shown are highly simplified schemes. After the second time sub-interval t _shot , the magnetic field usually oscillates.

Based on the perspective and partially sectioned representation of the 4th the measuring principle on which the invention is based is explained first. A flow measuring probe 101 comprises a generally circular cylindrical housing having a predetermined outer diameter 102 . This is adapted to the diameter of a hole in a wall of an in 4th is not shown pipeline and into which the flow measuring probe 101 is plugged in fluid-tight. A medium to be measured flows in the pipeline into which the flow measuring probe flows 101 immersed practically perpendicular to the direction of flow of the medium indicated by the wavy arrows 118 is indicated. A front end protruding into the medium 116 of the housing 102 is with a front body 115 sealed fluid-tight from insulating material. By means of one in the housing 102 arranged coil arrangement 106 a magnetic field reaching through the end section into the medium can be generated 109 produce. One at least partially made of a soft magnetic material in the housing 102 arranged coil core 111 ends at or near the end section 116 . A field feedback body 114 showing the coil assembly 106 and the coil core 111 encloses, the magnetic field reaching through from the end section is set up for this purpose 109 in the housing 102 traced back. The coil core 111 , the pole piece 112 and the field feedback body 114 are each field guide body 110 , which together form a field guidance arrangement 105 form. A first and a second measuring electrode forming a galvanic contact with the medium to be conveyed 103 , 104 form the device for detecting a measuring voltage induced in the medium and are in the front body 115 arranged and touch the medium just like the outer walls of the housing. At the measuring electrodes 103 , 104 an electrical voltage induced on the basis of Faraday's law of induction can be tapped by means of a measuring and / or evaluation unit. This is maximum when the flowmeter probe 101 is installed in the pipeline in such a way that one of the two measuring electrodes 103 , 104 intersecting straight line and a longitudinal axis of the flow measuring probe spanned plane perpendicular to the flow direction 118 or the longitudinal axis of the pipeline. An operating circuit 107 is with the coil assembly 106 , especially with the primary coil 113 electrically connected and set up a clocked operating signal to the primary coil 113 to impress in order to create a pulsed magnetic field 109 to create. According to the invention, the magnetic-inductive flow measuring probe 101 a device for detecting a test variable which depends on the magnetic field and / or on a change in the magnetic field over time. This is in the housing according to the configuration shown 102 arranged and as a secondary coil 119 formed, which is also like the primary coil 113 on the coil core 111 is arranged. The regulator circuit 10 is set up to regulate at least one of the operating signal parameters of the operating signal as a function of a measured value of the test variable so that a measured value of the test variable or a measured value of a variable dependent on the test variable does not deviate from a predetermined target value.

List of reference symbols

1

electromagnetic flowmeter

2

Measuring tube

3

Support tube

4th

Liner

5

Device for generating a magnetic field

6th

Primary coil

7th

Operating circuit

8th

Device for tapping an induced measurement voltage

9

Device for detecting a test variable

10

Regulator circuit

11

Operating signal

12th

course

13th

Secondary coil

14th

Coil core

15th

Recording of the primary coil

16

Recording of the secondary coil

17th

Measuring electrode

18th

Measuring electrode

19th

Level monitoring electrode

20th

Reference electrode

21

Pole piece

22nd

Field return

23

Measuring circuit

24

Evaluation circuit

101

Magnetic-inductive flow measuring probe

102

casing

103

Measuring electrode

104

Measuring electrode

105

Field guidance arrangement

106

Coil arrangement

107

Operating circuit

109

Magnetic field

110

Field leadership body

111

Coil core

112

Pole piece

113

Primary coil

114

Field feedback body

115

Front body

116

End section

118

Direction of flow of the medium

119

Secondary coil

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2014/001026 A1 [0005, 0021]

Claims (12)

Magnetic-inductive flow measuring device for determining a flow rate-dependent measured variable of a flowable medium, comprising: - A device (5) for generating a magnetic field, the device (5) for generating the magnetic field comprising a primary coil (6) and an operating circuit (7) for applying an operating signal (11) to the primary coil (6); - A device (8) for tapping a measuring voltage induced in the flowable medium, - A device (9) for detecting a test variable, the test variable depending at least on the magnetic field and / or on a change in the magnetic field over time; - A regulator circuit (10) for regulating the operating signal (11) as a function of the determined test variable, the regulator circuit (10) being set up to regulate at least one operating signal parameter of the operating signal (11) so that a measured value of the test variable does not differ from a predetermined one Setpoint deviates. Electromagnetic flow measuring device according to Claim 1 , the operating signal comprising a voltage with a time-variable curve (12) which is divided into time intervals (t), a sign of an applied voltage changing in successive time intervals, the time intervals (t) each having a first time sub-interval (t _hold ), wherein in a time interval the curve (12) comprises a first voltage (U _{hold ) that is constant, in particular over the entire duration of the first time sub-interval (t hold} ), which is applied to the primary coil (6) during the first time sub-interval (t _hold) is applied, with induced measurement voltages, which are determined in the first time sub-interval (t _hold ) are used to determine the flow velocity-dependent measured variable. Electromagnetic flow measuring device according to Claim 2 Wherein the time intervals (t) respectively a second time sub-interval (t _shot), wherein in a time interval of the voltage waveform (12), preferably in particular over the entire duration of the second time portion interval (t _shot) constant second voltage (U _shot) is applied , which is applied to the primary coil (6) during the second time sub-interval (t _{shot ), the second voltage (U shot} ) being greater than the first voltage (U _hold ), the first time sub-interval (t _hold ) being applied to the voltage curve second time sub-interval (t _shot ) follows, a duration of the second time sub-interval (t _shot ) being less than a duration of the first time sub-interval (t _hold ). Electromagnetic flow measuring device according to at least one of the preceding claims, wherein the at least one operating signal parameter is the first voltage (U _hold ), the second voltage (U _shot ), a duration of the time interval (t), a duration of the first time _{sub-interval (t hold} ), comprises a duration of the second time interval (t _shot ) and / or a controlled variable dependent on _{the first voltage (U hold} ) and the second voltage (U _shot). Magnetic-inductive flow measuring device according to at least one of the preceding claims, wherein the regulator circuit (10) is set up _{to regulate the first voltage (U hold} ) of a time interval (t) as a function of the measured value of the test variable detected in particular in the immediately preceding time interval, that the deviation of the measured value of the test variable from the nominal value becomes smaller or assumes a value from a predetermined tolerance range. Electromagnetic flow measuring device according to Claim 5 , the duration of the second time sub-interval (t _shot ) being a variable and controllable variable. Magnetic-inductive flow measuring device according to at least one of the preceding claims, wherein the device (9) for detecting the test variable comprises a secondary coil (13), wherein the test variable comprises a voltage induced in the secondary coil (13) and / or a variable that is dependent on the induced voltage. Electromagnetic flow measuring device according to Claim 7 , wherein the device (5) for generating the magnetic field comprises a coil core (14), the primary coil (6) and the secondary coil (13) each having a receptacle (16), the coil core (14) extending through the receptacle (16 ) the secondary coil (13) and the primary coil (6) extends. Electromagnetic flow measuring device according to Claim 3 , the duration of the second time interval (t _shot ) being regulated in such a way that a determined value of a variable dependent on the test variable assumes a target value _{within the duration of the second time interval (t shot).} Electromagnetic flow measuring device according to Claim 3 until 9 , an amount of the second voltage (U _shot ) assuming a constant value over the course (12). Magnetic-inductive flow measuring device according to at least one of the preceding claims, wherein the magnetic-inductive flow measuring device is designed as a magnetic-inductive flow measuring device (1), comprising a measuring tube (2) for guiding the flowable medium. Electromagnetic flow measuring device according to at least one of the Claims 1 until 10 , wherein the magneto-inductive flow measuring device is designed as a magneto-inductive flow measuring probe (101) for insertion into a lateral opening of a pipeline, comprising a housing (102) to which the medium is applied, the device (5) for generating the magnetic field in the housing is arranged.

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