MAGNETICALLY INDUCTIVE FLOW MEASURING DEVICE AND METHOD FOR DETERMINING A FILL LEVEL

Abstract

A magnetically inductive flow measuring probe includes a housing; at least one measuring electrode for forming a galvanic contact with the medium and for tapping an induced voltage in the medium; a device for generating a magnetic field, wherein the device is arranged in the housing, wherein the device comprises a field guide assembly and a coil arrangement, wherein the field guide assembly functions as a sensor electrode for capacitively determining and/or monitoring a fill level of the medium in the tube line or the measuring tube. The present disclosure also relates to a method for determining a fill level of a medium in a measuring tube or in a tube line using the magnetically inductive flow measuring device.

Claims

1-12. (canceled)

13. A magnetically inductive flow measuring device for determining a flow velocity-dependent measured variable of a flowable medium in a measuring tube or in a tube line, comprising: a housing; a device for tapping a measurement voltage induced in the flowable medium, and forming a galvanic contact with the medium using at least one electrode; a device for generating a magnetic field, wherein the device is arranged in the housing, wherein the device comprises a field guiding assembly and a coil arrangement, wherein the field guiding assembly serves as a sensor electrode for capacitively determining or monitoring a fill level of the medium in the tube line or the measuring tube.

14. The magnetically inductive flow measuring device of claim 13, comprising: an operating circuit arranged in the housing, wherein the operating circuit is electrically connected to the field guiding assembly, wherein the operating circuit is configured to supply a temporally alternating excitation signal to the field guiding assembly, to receive a response signal from the field guiding assembly, and to make a statement about the fill level of the medium in the tube line or the measuring tube at least from the response signal.

15. The magnetically inductive flow measuring device of claim 13, wherein the magnetically inductive flow measuring device includes a magnetically inductive flow measuring probe for insertion into a tube line through which a medium can flow, wherein the magnetically inductive flow measuring probe has a housing that is cylindrical and is configured to be supplied with the medium, wherein the housing has an end portion that comprises an at least partially electrically insulating wall, wherein the at least two measuring electrodes are arranged in the wall of the housing, wherein the device for generating the magnetic field is configured to generate a magnetic field penetrating the end portion.

16. The magnetically inductive flow measuring device of claim 15, wherein the field guide assembly comprises a coil core, a pole shoe or a field return body.

17. The magnetically inductive flow measuring device of claim 15, wherein the magnetically inductive flow measuring probe comprises an annular electrode arranged around the wall of the housing, wherein the operating circuit is configured to impress the excitation signal between the annular electrode and the field guide body.

18. The magnetically inductive flow measuring device of claim 15, wherein the magnetically inductive flow measuring probe is suitable for being fastened via a metallic connection body in a tube line, in particular a metallic tube line, wherein the magnetically inductive flow measuring probe is designed in such a way that, when the magnetically inductive flow measuring probe is connected to the connection body, an electrical contact forms between the operating circuit and the connection body, wherein the operating circuit is configured to impress the excitation signal between the connection body and the field guide body.

19. The magnetically inductive flow measuring device according to claim 15, wherein the field system has a field return body, which is connected to an end portion of the coil core.

20. The magnetically inductive flow measuring device of claim 15, wherein at least a segment of the field guide body contacts the electrically insulating wall of the housing.

21. The magnetically inductive flow measuring device of claim 15, wherein the wall of the housing has an outer surface that can be impinged by the medium, wherein a cutout of the field guide assembly is spaced apart from the outer surface exclusively by the wall of the housing.

22. The magnetically inductive flow measuring device of claim 15, wherein the operating circuit is connected to the coil arrangement and is configured to generate a clocked magnetic field with excitation phases and with rest phases that are respectively located between two excitation phases and in which substantially no coil current flows, wherein in one of the rest phases, the excitation signal is generated and the corresponding response signal is received.

23. The magnetically inductive flow measuring device of claim 15, wherein the operating circuit is configured to determine a measured value of an electrical capacitance of the field guide assembly to the medium at least on the basis of the response signal and to determine information regarding the fill level on the basis of a deviation of the determined measured values from a reference capacitance.

24. A method for determining a fill level in a tube line using a magnetically inductive flow measuring device, of claim 13, including method steps of: supplying an electrical, temporally alternating, excitation signal to a field guiding body, receiving an electrical reception signal from the field guide body, determining a measuring capacitance of the field guide body at least on the basis of the reception signal, and determining a fill level in a tube line or a measuring tube on the basis of the measuring capacitance.

Description

[0076] The invention is explained in greater detail with reference to the following figures. The following are shown:

[0077] FIG. 1: a perspective partially sectional view of a magnetically inductive flow measuring probe according to the prior art;

[0078] FIG. 2: a longitudinal section through an embodiment of the magnetically inductive flow measuring probe according to the invention inserted in a tube line;

[0079] FIG. 3: three views of an embodiment of the magnetically inductive flow measuring probe according to the invention; and

[0080] FIG. 4: a method sequence according to the invention for determining a fill level of a medium in a measuring tube or in a tube line using a magnetically inductive flow measuring device.

[0081] The measuring principle on which the invention is based is first explained on the basis of the perspective and partially sectional illustration of FIG. 1. A flow measuring probe 1 comprises a generally circular cylindrical housing 2 having a predetermined outer diameter. Said housing is adapted to the diameter of a bore, which is located in a wall of a tube line 8 (not shown in FIG. 1 but shown in FIG. 2) into which the flow measuring probe 1 is inserted in a fluid-tight manner. A medium to be measured flows in the tube line 8 and the flow measuring probe 1 is immersed into said medium practically perpendicularly to the flow direction of the medium, which is indicated by the wavy arrows 18. A front end 16 of the housing 2 that projects into the medium is sealed in a fluid-tight manner with a front body 15 made of insulating material. By means of a coil arrangement 6 arranged in the housing 2, a magnetic field 9 that extends through the end portion into the medium can be generated. A coil core 11, which at least partially consists of a soft magnetic material and is arranged in the housing 2, terminates at or near the end portion 16. A field return body 14 that surrounds the coil arrangement 6 and the coil core 11 is configured to return, into the housing 2, the magnetic field 9 extending through from the end portion. The coil core 11, the pole shoe 12 and the field return body 14 are each field guide bodies 10, which together form a field guide assembly 5. A first and a second galvanic measuring electrode 3, 4 are arranged in the front body 15 and contact the medium. An electrical voltage induced due to Faraday’s law of induction can be tapped at the measuring electrodes 3, 4 by means of a measurement and/or evaluation unit. This is at a maximum if the flow measuring probe is installed in the tube line such that a plane spanned by a straight line intersecting the two measuring electrodes 3, 4 and by a longitudinal axis of the flow measuring probe runs perpendicularly to the flow direction 18 or to the longitudinal axis of the tube line. An operating circuit 7 is electrically connected to the coil arrangement 6, in particular to the coil 13, and is configured to impress a clocked excitation signal to the coil in order to thus generate a clocked magnetic field 9.

[0082] FIG. 2 shows a longitudinal section of a magnetically inductive flow measuring probe 1 installed in a tube line 8. The flow measuring probe 1 is fastened in the tube line 8 in a fluid-tight manner by means of a screw-in connection 22, which is inserted into the tube wall 19 of the tube line 8 and is welded thereto, for example. This structure of the measuring point is particularly expedient, since the screw-in connection 22 can initially be inserted into the tube line 8 and welded therein, and only afterwards does the magnetically inductive flow measuring probe 1 have to be inserted with a connection body 20 into the screw-in connection 22, in turn screwed therein, and sealed by means of a seal. As a result of the installation, an unknown installation angle between the tube longitudinal axis and the electrode axis is produced. The two measuring electrodes 3, 4 are arranged on the end portion 16 symmetrically to a center of the end portion 16. The coil core 11 is designed to be fully cylindrical and oriented coaxially to the housing. The field return body 14 is hollow cylindrical and is in contact with one end of the coil core 11. The coil core 11, pole shoe 12 and field return body 14 are formed monolithically. An installation depth D indicates how deep the flow measuring probe 1 is inserted into the medium or projects into the tube line.

[0083] According to the invention, the operating circuit 7 is connected to the field guide assembly 5, in particular to a field guide body 10 of the field guide assembly 5. In the illustrated embodiment, the field guide assembly 5 is formed in one piece by a coil core 11, a pole shoe 12 and a field guide body 14. The operating circuit 7 is designed to generate an, in particular temporally alternating, excitation signal and to supply it to the field guide assembly 5 or the field guide body 14. In addition, the operating circuit 7 is configured to tap a response signal at the field guide assembly 5 or the field guide body 14 and to make a statement about the fill level of the medium in the tube line, at least as a function of the response signal. The excitation signal and the response signal each have an amplitude and a frequency. A statement about the fill level can be made on the basis of an amplitude difference. Alternatively, the operating circuit can be configured to determine a phase difference or a variable of the two signals dependent on the phase difference and to make a statement about the fill level therefrom. Alternatively, the operating circuit can be configured to determine the fill level on the basis of the frequency of the response signal. Alternatively, taking into account the excitation signal, the response signal and an equivalent circuit diagram, a measuring capacitance can be determined, on the basis of which conclusions can be drawn about the fill level.

[0084] FIG. 3 shows a side view of an embodiment of the front body 15 with a coil arrangement carrier 24 with mounted coil core 11, field return body 14 and contacting device 23. The front body 15 shown has all essential features of FIG. 1. In addition to the coil arrangement carrier 24 and to the front body 5, a field return body 14, a coil core 11, which extends through the cross-sectional areas of the coil 13, and a contacting device 23 are shown.

[0085] Furthermore, FIG. 3 shows a coil core 11 with a field return body 14, which together form the sensor electrode. The coil core 11 is cylindrical and the field return body 14 has the basic shape of a bent strip. In addition, the field return body 14 has a symmetry number of 2. The field return body 14 and the coil core 11 can or are monolithically formed according to the depicted embodiment. Alternatively, the field guide assembly can consist of at least two assembled individual components. The field guide assembly is arranged on a front body and extends partially through an opening of a coil carrier. Two measuring electrodes are arranged in the front body and are connected via a contacting device 23 to a measurement and/or evaluation circuit (not shown). The contacting device 23 is formed from a circuit board, in particular from a flexible printed circuit board, on which a measurement and/or operating circuit can be arranged.

[0086] FIG. 3 also shows two perspective views of the front body 15 mounted on an end portion 15 of a housing 2. The housing 2 has a cylindrical basic shape. The housing 2 can be cast with a casting compound for fixing the field system. The front body 15 of the depicted embodiment has a measuring electrode arrangement with two measuring electrodes 3, 4 located on a diameter of the front body 15. The front body 15 is pressed in a medium-sealing manner into the housing 2 or is arranged, in particular compressed, in a medium-tight manner with a seal. A housing casing of the housing is designed to be electrically conductive and serves as a reference electrode 17. In addition, the operating circuit 7 electrically connected to the field guide assembly is co-cast in the housing. Alternatively, it can also be arranged outside the housing 2.

[0087] FIG. 4 shows a method sequence according to the invention for determining a fill level of a medium in a measuring tube using a magnetically inductive flow measuring probe. In a first method step A, a temporally alternating excitation signal is applied to a field guiding assembly. The field guiding assembly comprises at least one field guiding body which is formed by at least one coil core and/or at least one pole shoe. The excitation signal is supplied via an operating circuit which is electrically connected to the field guiding assembly or to at least one of the field guiding bodies. In a further method step B, an electrical response signal is received by means of the operating circuit from the field guide assembly or the field guide body. In this case, supplying and receiving take place at a single field guiding body. Alternatively, the excitation signal can be applied to a first field guiding body and the response signal can be received at a second field guiding body. On the basis of the response signal, taking into account the excitation signal, in a further method step C, a measuring capacitance or a variable dependent on the electrical capacitance between sensor electrode and medium is determined, which is dependent on the fill level of the medium in the measuring tube. In a last method step D, a fill level is then determined as a function of the determined measuring capacitance or the variable dependent on the electrical capacitance between sensor electrode and medium. Alternatively, a deviation of the, for example, determined measuring capacitance from a reference value or a reference range can be determined and a warning message can optionally be output or transmitted to an evaluation circuit, which is configured to determine a volumetric flow rate as a function of the induced measurement voltage.

TABLE-US-00001 List of reference characters 1 Magnetically inductive flow measuring probe 2 Housing 3 Measuring electrode 4 Measuring electrode 5 Field guide assembly 6 Coil arrangement 7 Operating circuit 8 Tube line 9 Magnetic field 10 Field guide body 11 Coil core 12 Pole shoe 13 Coil 14 Field return body 15 Front body 16 End portion 17 Reference electrode 18 Flow direction of the medium 19 Tube wall 20 Connection body 21 Tube longitudinal axis 22 Screw-in connection 23 Contacting device 24 Coil arrangement carrier