Title of Invention

MAGNETO-INDUCTIVE FLOW MEASURING DEVICE

Abstract

The invention relates to a magnetically inductive flowmeter (1) comprising a measuring tube (2), which is essentially traversed by a medium (11) in the direction of the measuring tube axis (16), an assembly of magnets (6, 7), which generates a magnetic field (H) that penetrates the measuring tube (2) and runs essentially perpendicular to the measuring tube axis (16), a first measuring electrode (3) and a second measuring electrode (4), said measuring electrodes (3, 4) being positioned in the measuring tube (2) along a connecting line, which is aligned essentially perpendicularly to the measuring tube axis (16) and to the magnetic field (H) and an evaluation and control unit (12), which determines the volumetric flow or mass flow of the medium (11) through the measuring tube (2) using the measured voltage that is captured at the measuring electrodes (3, 4). To increase the measuring accuracy of the multi-parameter flowmeter (1), the first measuring electrode (3) is produced from a first material (A) and the second measuring electrode (4) from a second material (C) that is different from the first material (A). The control and evaluation unit (12) determines the respective d.c. voltage fraction (UG) of the voltage (U3, U4) that is captured at the two electrodes (3, 4) in relation to a reference potential (FR) and provides information that is specific to the medium using the d.c. voltage fraction (UG).

Full Text

FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13) 1. TITLE OF INVENTION MAGNETO-INDUCTIVE FLOW MEASURING DEVICE 2. APPLICANT(S) a) Name b) Nationality c) Address ENDRESS+HAUSER FLOWTEC AG SWISS Company KAEGENSTRASSE 7, CH-4153 REINACH, SWITZERLAND 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed : - The invention relates to a magneto-inductive flow measuring device, including: A measuring tube, through which a medium flows essentially in the direction of the measuring tube axis; a magnet arrangement, which produces an alternating magnetic field passing through the measuring tube and directed essentially perpendicularly to the axis of the measuring tube; a first measuring electrode and a second measuring electrode; wherein the measuring electrodes are positioned in the measuring tube on a connecting line, which is directed essentially perpendicularly to the axis of the measuring tube and to the magnetic field; and a control/ evaluation unit, which, on the basis of the measurement voltage tapped from the measuring electrodes, determines the volume and/or mass flow, e.g. flow rate, of the medium through the measuring tube. Magneto-inductive flow measuring devices utilize the principle of electrodynamic induction for measuring volumetric flow: Charge carriers of the medium moved perpendicular to a magnetic field induce a voltage in measuring electrodes arranged likewise essentially perpendicularly to the direction of flow of the medium. This measurement voltage induced in the measuring electrodes is proportional to the flow velocity of the medium averaged over the cross section of the measuring tube; it is, thus, proportional to the volume flow rate. In the case of known density of the medium, it is then also possible to ascertain the mass flow of the medium flowing through the measuring tube. The measuring electrodes are usually coupled with the medium either galvanically or capacitively. US 5,677,496 and EP 1 249 687 Al disclose that, besides the alternating voltage relevant for the actual flow measurement, also appearing on the measuring electrodes is a direct voltage portion caused by disturbance potentials. In order to take into consideration the influence of these disturbance potentials, voltages are sensed on the two measuring electrodes relative to a reference potential. The reference potential is usually ground- or earth-potential. Then, a value for the direct voltage portion of the voltage tapped on the two measuring electrodes relative to the reference potential is ascertained. In US 5,677,496, the direct voltage portion is used for correcting the actual measurement voltage signal. In this way, a voltage value is obtained, which, now no longer error laden, is a direct measure for the volume flow of the medium through the measuring tube. Additionally provided in EP 1 249 687 Al is an output system, with which a value for the direct voltage portion of the voltages sensed on the two measuring electrodes, in each case relative to the reference potential, is made available to the user for further processing. This solution has, moreover, been implemented since the year 2000 in the PROM AG 50/53 flow measuring device offered and sold by the present assignee. Additionally described in EP 1 249 687 Al is a method for ascertaining, with the help of the direct voltage portions of the voltages sensed on the measuring electrodes relative to the reference potential, the pH-value of the medium. Problematic in the case of the method disclosed in EP 1 249 687 Al is the constancy of the reference potential needed for a sufficiently high accuracy of measurement. As described in EP 1 249 687 Al, the electrochemical disturbance voltage is measured relative to the reference potential, especially relative to earth-potential. Inherent in this is that the quality of the pH-value measurement stands and falls with the constancy of the reference potential. Calibration of magneto-inductive measuring devices occurs, usually, not on-site, but, instead, before shipping, at the production site. If, for example, the connection pipelines used during calibration of the measuring device differ from the connection pipelines used later during operation of the flow measuring device at the measuring site, then the reference potential changes in an undefined manner, since the reference potential is influenced not only by the material of the reference electrode, but also by the material of the pipeline inlet and outlet. For the pH-value measurement, this means that the issued pH-value is burdened with a large measurement error, thus being more an estimate than a reliable, measured value. An object of the invention is to so embody a magneto-inductive flow measuring device, that the electrochemical, disturbing voltage present on the measuring electrodes of the flow measuring device is independent of the reference potential. The object is achieved in a first form of embodiment of the magneto-inductive flow measuring device of the invention by features including that the first measuring electrode comprises a first material A, the second measuring electrode comprises a second material C different from the first material A, the control/evaluation unit ascertains the direct voltage portion of the voltages sensed on the two measuring electrodes, in each case, relative to a reference potential, and the control/evaluation unit makes medium-specific information available on the basis of the direct voltage portion. Preferably, the reference potential is earth potential. The object is achieved in a second form of embodiment of the magneto-inductive flow measuring device of the invention by features including that the first measuring electrode comprises a first material A, the second measuring electrode comprises a second material C different from the first material A, the control/evaluation unit ascertains the direct voltage difference between the two measuring electrodes, and the control/evaluation unit makes available medium-specific information on the basis of the direct voltage difference. For making the measurement error smaller, in an advantageous further development of the flow measuring device of the invention, the control/evaluation unit can average the direct voltage portion, or the direct voltage difference, over a plurality of measuring periods. In an advantageous further development of the magneto-inductive flow measuring device of the invention, the medium-specific information involves a physical variable or an electrochemical variable. In the case of an electrochemical variable, preferably ion concentration, an electrochemical potential or the pH-value of the medium is ascertained. Examples of a physical variable include information concerning the impedance or the conductivity of the medium flowing through the measuring tube. Especially advantageous in connection with the present invention is when, on the basis of historical data, information on changes at the measuring device or in the process are made available. To this end, in an embodiment of the magneto-inductive flow measuring device of the invention, a memory unit is provided, in which the ascertained, medium-specific information, or the information concerning the direct voltage portion, is stored as a function of time; on the basis of change over time of the medium-specific information, a report is made available, which is correlated with a correspondingly predetermined change at the flow measuring device or in the process. Especially stored in the memory unit is at least one desired value for the medium- specific information; if the measured or ascertained, actual value exceeds or falls beneath the desired value or exceeds or falls beneath a tolerance range about the desired value, then a corresponding report is issued, stored or forwarded to a superordinated, control facility. The invention will now be explained in more detail on the basis of the drawing, the figures of which show as follows: Fig. 1 schematic drawings of magneto-inductive flow measuring devices of the invention, a) without reference electrode, and b) with reference electrode; and Fig. 2 a schematic drawing of the voltage tapped on the measuring electrodes. Figs, la and lb are schematic drawings of magneto-inductive flow measuring devices of the invention. While, in Fig. la, an embodiment is presented without reference electrode, Fig. lb shows an embodiment with a reference electrode 5. Since this is, fundamentally, the only difference, attention in the following will be directed to the embodiment of Fig. la. Flow measuring device 1 includes a measuring tube 2, through which a medium 11 flows in the direction of the measuring tube axis 16. In order to be able to make use of the magneto-inductive measuring principle, the medium 11 is at least slightly electrically conductive, while measuring tube 2 is made of an electrically non-conductive material, or is at least lined internally with a non-conductive material. Arranged in the two lateral regions of the measuring tube 2 are the two, diametrally opposed, measuring electrodes 3, 4. According to the invention, the two measuring electrodes 3, 4 are made of, or are coated with, different materials, materials A and C. If present (Fig. lb), the reference electrode 5, which lies preferably at a ground- or earth-potential, is located in the lower region of the measuring tube 2. As a result of the alternating magnetic field B directed essentially perpendicularly to the flow direction of the medium 11 and produced by the two diametrally opposed electromagnets 6, 7, charge carriers located in the medium 11 migrate to the oppositely poled, measuring electrodes 3, 4. The measurement voltage U which is established on the measuring electrodes 3, 4 is proportional to the flow velocity of the medium 11 averaged over the cross section of the measuring tube 2, i.e. it is a measure for the volume flow rate of the medium 11 in the measuring tube 2. The measurement voltage U is tapped either between the two measuring electrodes 3, 4 or between the two measuring electrodes 3, 4, respectively, and the reference electrode 5 (Fig. lb), with, in the last case, the reference potential being dropped out of the equation by taking the difference between the two measurements. A measurement amplifier arrangement for a magneto-inductive flow measuring device 1 is described in EP 0 814 324 Bl. Measuring tube 2 is connected into the pipeline using connecting elements, e.g. flanges (not shown), with one side of the pipeline providing the feed for the measuring tube and the other side the drain. As evident from Fig. 2, there is, on the measuring electrodes 3, 4, besides the actual, alternating, measurement voltage U(t) relevant for the flow measurement, also a direct voltage portion UD formed by electrochemical and, thus, medium-dependent, disturbing potentials. The direct voltage portion UD is superimposed on the actual measurement voltage U(t). In order to measure the influence of the disturbing potentials, or the direct voltage portion UD, measurement voltages U3(t), U4(t), respectively, on the two measuring electrodes 3, 4 are sensed between the measuring electrodes 3, 4, respectively, and the reference electrode 5. Then, in the control/evaluation unit 12, the difference between the two ascertained measurement voltages U3(t), Ut(t) is formed (Fig. lb). Due to the difference forming, i.e. U3(t) - U4(t), the reference potential OR drops out, so that the measurement voltage U(t) corresponds to the difference of the two measuring electrode potentials O3 - O4. Consequently, the actual measured value, which is used for ascertaining the volume flow and the electrochemical, or physical, variable, is independent of the reference potential OR. The reference potential OR is usually the ground- or earth-potential. Alternatively, the voltage between the two measuring electrodes 3, 4 is registered (Fig. la). Uncontrolled changes of the reference potential FR, for example as a result of the character of the pipeline system at the site of installation (e.g. the pipeline system is made of another material than the measuring tube 2) have, consequently, no effect on the measuring accuracy of the multi-parameter flow measuring device 1. In the two illustrated variants of the flow measuring device 1 of the invention, the measuring electrodes 3, 4, and the reference electrode 5, in the case where such is present, are in direct contact with the medium. The measuring electrodes 3, 4, and the reference electrode 5, in the case where such is present, are connected with the control/evaluation unit 12 via connecting lines 8, 9,10. The control/evaluation unit 12 is connected with an output unit 14 via the connecting line 13. Additionally, the pole reversal of the magnetic field B, i.e. the electromagnets 6, 7, is accomplished via the control/evaluation unit 12. Associated with the control/evaluation unit 12 is a memory unit 15. In the control/evaluation unit 12, a desired value DES is specified for at least one physical or electrochemical variable, and, where appropriate, also for different media 11. The desired value DES, or the desired values DES, of the relevant physical or electrochemical variable(s) can also be specified at the time of startup of the device, by storing, as the desired value DES, the actual value ACT measured at such time. If the measured, actual value ACT changes in the course of time, then, from the change, conclusions can be drawn regarding changes at the flow measuring device 1 or in the process. If e.g. the pH-value changes abruptly, then this is an indication that the composition of the medium 11, or the medium 11 itself, has changed. The same is true as regards an abrupt change in the conductivity, while, in contrast, a creeping change would point to a fouling of the measuring electrodes. If the arising deviation lies outside of a predetermined tolerance TOL, then a corresponding report is issued at the display unit 14. Alternatively, a warning can be sent via a bus to a superordinated control room. List of Reference Characters 1 flow measuring device 2 measuring tube 3 measuring electrode 4 measuring electrode 5 reference electrode 6 electromagnet 7 electromagnet 8 connecting line 9 connecting line 10 connecting line 11 medium 12 control/evaluation unit 13 connecting line 14 output unit 15 memory unit 16 measuring tube axis 17 A/D converter 18 A/D converter WE CLAIM: 1. Magneto-inductive flow measuring device (1) comprising: A measuring tube (2), through which a medium (11) flows essentially in a direction of a measuring tube axis (16); a magnet arrangement (6, 7), which produces a magnetic field (H) passing through the measuring tube (2) and extending essentially perpendicularly to the measuring tube axis (16); a first measuring electrode (3) and a second measuring electrode (4); wherein the measuring electrodes (3, 4) are positioned in the measuring tube (2) on a connecting line, which is directed essentially perpendicularly to the measuring tube axis (16) and to the magnetic field (H); and an evaluation/ control unit (12), which ascertains, on the basis of a measurement voltage tapped on the measuring electrodes (3, 4), the volume- and/or mass-flow of the medium (11) through the measuring tube (2); characterized in that the first measuring electrode (3) comprises a first material (A), the second measuring electrode (4) comprises a second material (C) different from the first material (A), the control/evaluation unit (12) ascertains the direct voltage portion (UD) of the voltages (U3, U4) tapped on the two measuring electrodes (3, 4) relative to a reference potential (OR), and the control/evaluation unit (12) makes available, on the basis of the direct voltage portion (UD), medium-specific information. 2. Apparatus as claimed in claim 1, characterized in that the reference potential (OR) is earth potential. 3. Magneto-inductive flow measuring device (1) comprising: A measuring tube (2), through which a medium (11) flows essentially in a direction of a measuring tube axis (16); a magnet arrangement (6, 7), which produces a magnetic field (B) passing through the measuring tube (2) and extending essentially perpendicularly to the measuring tube axis (16); a first measuring electrode (3) and a second measuring electrode (4); wherein the measuring electrodes (3, 4) are positioned in the measuring tube (2) on a connecting line, which is directed essentially perpendicularly to the measuring tube axis (16) and to the magnetic field (B); and an evaluation/control unit (12), which ascertains, on the basis of a measurement voltage tapped on the measuring electrodes (3, 4), the volume- and/or mass-flow of the medium (11) through the measuring tube (2); characterized in that the first measuring electrode (3) comprises a first material (A), the second measuring electrode (4) comprises a second material (C) different from the first material (A), the control/evaluation unit (12) ascertains the direct voltage difference (UD) between the two measuring electrodes (3, 4), and the control/ evaluation unit (12) makes available, on the basis of the direct voltage difference (UD), medium-specific information. 4. Apparatus as claimed in claim 1 or 3, characterized in that the control/evaluation unit (12) averages the direct voltage portion (UD), or the direct voltage difference (UD), over a plurality of measuring periods. 5. Apparatus as claimed in claim 1 or 3, characterized in that the medium-specific information concerns a physical variable or an electrochemical variable. 6. Apparatus as claimed in claim 5, characterized in that the electrochemical variable is an ion concentration, an electrochemical potential or a pH-value of the medium. 7. Apparatus as claimed in claim 5, characterized in that the physical variable is impedance or conductivity of the medium (11) flowing through the measuring tube (2). 8. Apparatus as claimed in claim 1 or 3, characterized in that a memory unit (15) is provided, in which the ascertained medium-specific information (INFO) is stored as a function of time (t), and the control/ evaluation unit (12) provides, on the basis of a time change of the medium specific information (INFO), a report correlated with a correspondingly specified change at the flow measuring device (1) or in the process. 9. Apparatus as claimed in claim 8, characterized in that at least one desired value (DES) for the medium-specific information (INFO) is stored in the memory unit (15) and a display unit (14) is provided, which issues a report, when the measured or registered, actual value (ACT) exceeds or falls beneath the desired value (DES) or a tolerance (TOL) specified around the desired value (DES). Dated this 4th day of December, 2007 ABSTRACT The invention relates to a magneto-inductive flow measuring device (1), including: A measuring tube (2), through which a medium (11) flows essentially in a direction of a measuring tube axis (16); a magnet arrangement (6, 7), which produces a magnetic field (H) passing through the measuring tube (2) and extending essentially perpendicularly to the measuring tube axis (16); a first measuring electrode (3) and a second measuring electrode (4); wherein the measuring electrodes (3, 4) are positioned in the measuring tube (2) on a connecting line, which is directed essentially perpendicularly to the measuring, tube axis (16) and to the magnetic field (11); and an evaluation/control unit (12), which ascertains, on the basis of a measurement voltage tapped on the measuring electrodes (3, 4), the volume- and/or mass-flow of the medium (11) through the measuring tube (2). In order to increase the measuring accuracy of the multi-parameter flow measuring device (1), the first measuring electrode (3) is made of a first material (A) and the second measuring electrode (4) is made of a second material (C) different from the first material (A); the control/evaluation unit (12) ascertains the direct voltage portion (Up) of the voltages (Lb, Lb) tapped on the two measuring electrodes (3, 4) relative to a reference potential (OK), and makes available, on the basis of the direct voltage portion (Up), medium-specific information.

Documents:

2054-mumnp-2007-abstract.doc

2054-mumnp-2007-abstract.pdf

2054-MUMNP-2007-CANCELLED PAGES(14-9-2011).pdf

2054-MUMNP-2007-CLAIMS(AMENDED)-(14-9-2011).pdf

2054-MUMNP-2007-CLAIMS(AMENDED)-(9-12-2011).pdf

2054-MUMNP-2007-CLAIMS(MARKED COPY)-(9-12-2011).pdf

2054-mumnp-2007-claims.doc

2054-mumnp-2007-claims.pdf

2054-mumnp-2007-correspondence(13-3-2008).pdf

2054-MUMNP-2007-CORRESPONDENCE(8-9-2008).pdf

2054-mumnp-2007-correspondence-others.pdf

2054-mumnp-2007-correspondence-received.pdf

2054-mumnp-2007-description (complete).pdf

2054-MUMNP-2007-DRAWING(14-9-2011).pdf

2054-MUMNP-2007-DRAWING(9-12-2011).pdf

2054-mumnp-2007-drawings.pdf

2054-mumnp-2007-form 1(13-3-2008).pdf

2054-mumnp-2007-form 2(title page)-(4-12-2007).pdf

2054-MUMNP-2007-FORM 3(14-9-2011).pdf

2054-MUMNP-2007-FORM 5(14-9-2011).pdf

2054-MUMNP-2007-FORM PCT-ISA-237(14-9-2011).pdf

2054-mumnp-2007-form-1.pdf

2054-mumnp-2007-form-18.pdf

2054-mumnp-2007-form-2.doc

2054-mumnp-2007-form-2.pdf

2054-mumnp-2007-form-26.pdf

2054-mumnp-2007-form-3.pdf

2054-mumnp-2007-form-5.pdf

2054-MUMNP-2007-GENERAL POWER OF ATTORNEY(14-9-2011).pdf

2054-MUMNP-2007-OTHER PCT DOCUMENT(14-9-2011).pdf

2054-MUMNP-2007-PCT-IB-338(8-9-2008).pdf

2054-MUMNP-2007-PCT-ISA-237(8-9-2008).pdf

2054-mumnp-2007-pct-search report.pdf

2054-MUMNP-2007-POWER OF ATTORNEY(9-12-2011).pdf

2054-MUMNP-2007-REPLY TO EXAMINATION REPORT(14-9-2011).pdf

2054-MUMNP-2007-REPLY TO HEARING(9-12-2011).pdf

2054-MUMNP-2007-US DOCUMENT(9-12-2011).pdf

2054-mumnp-2007-wo international publication report(4-12-2007).pdf

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