EP1649251A1 - Procede de determination magneto-inductive du debit d'un agent - Google Patents
Procede de determination magneto-inductive du debit d'un agentInfo
- Publication number
- EP1649251A1 EP1649251A1 EP04741101A EP04741101A EP1649251A1 EP 1649251 A1 EP1649251 A1 EP 1649251A1 EP 04741101 A EP04741101 A EP 04741101A EP 04741101 A EP04741101 A EP 04741101A EP 1649251 A1 EP1649251 A1 EP 1649251A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- measuring
- measuring electrode
- time
- electrode
- determined
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
- G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
- G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
- G01F1/60—Circuits therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/12—Cleaning arrangements; Filters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
- G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
Definitions
- the invention relates to a method for the magnetic-inductive determination of the flow rate of a medium which flows through a measuring tube in the direction of the measuring tube axis, the measuring tube being penetrated by a magnetic field substantially perpendicular to the measuring tube axis, at least one being arranged essentially perpendicular to the measuring tube axis Measuring electrode, a measuring voltage is induced and the induced measuring voltage provides information about the volume flow of the medium in the measuring tube. Furthermore, the invention relates to a corresponding device.
- Magnetic-inductive flowmeters use the principle of electrodynamic induction for volumetric flow measurement: Charge carriers of the medium, which are moved perpendicular to a magnetic field, induce a voltage in measuring electrodes which are also arranged essentially perpendicular to the direction of flow of the medium. This voltage induced in the measuring electrodes is proportional to the flow velocity of the medium averaged over the cross section of the tube; it is therefore proportional to the volume flow.
- the measuring electrodes are either galvanically or capacitively coupled to the medium. If the measuring electrodes come into contact with the medium, a coating forms on the surface of the measuring electrodes over time. As a result of the deposit formation, the flow meter malfunctions. If the covering consists of a non-conductive material, the flow meter no longer delivers any measured values at all.
- the invention is generally also for the detection of others Malfunctions that can occur on a magnetic inductive flow meter can be used.
- EP 0 337 292 proposes to clean the measuring electrodes at predetermined time intervals by applying an electrical direct or alternating voltage.
- the known automatic cleaning of the measuring electrodes also has disadvantages: First, it cannot be used universally for coverings made of any material - it only works when removing conductive coverings , Furthermore, the automatic cleaning takes place preventively at predetermined time intervals; So there is no guarantee that cleaning will take place at a time when it is absolutely necessary.
- Preventive cleaning of the measuring electrodes is disruptive and undesirable for several reasons: for example, no volumetric flow measurement is possible within a certain period of time after the cleaning process, since the measuring voltage at the measuring electrodes first has to build up again. Furthermore, the power supply for the purpose of cleaning the measuring electrodes takes place for a predetermined period of time, since the degree of deposit formation at the time of cleaning is largely unknown. It is therefore up to chance or the corresponding experience of the operating personnel whether the desired optimal condition of the measuring electrodes is actually achieved after the automatic cleaning has been carried out. In the normal case it can be assumed that after the automatic cleaning has taken place there is either still a coating on the measuring electrode or that the measuring electrode has been damaged by applying the cleaning voltage for too long.
- the interruptions in the measuring process are even more serious if the measuring electrodes are precautionary of non-conductive coatings have to be exempted.
- the service life of the flow meter is even longer in this case, since the removal of non-conductive deposits can only be done mechanically, ie the flow meter must be removed and the measuring electrodes must be cleaned by hand.
- a solution has become known from EP 1 108 988 A1 as to how a deposit formation can be identified in a targeted and automatic manner in order then to be removed from the measuring electrode if necessary.
- a defined test signal is given to the measuring electrode; on the basis of the response signal to the defined test signal and / or on the basis of a reference variable determined from the response signal on the defined test signal, it is determined whether the measuring electrode supplies correct measured values.
- the response signal to the defined test signal or the reference variable determined from the response signal to the defined test signal is referred to below as the actual value for the sake of simplicity.
- the method according to the invention detects a creeping malfunction of the flow meter at an early stage, so that it can subsequently be counteracted in a targeted manner.
- this publication proposes to compare the respective actual value with a predetermined target value and to display, output and / or store a malfunction if the actual value deviates from the target value.
- the known solution brings the desired success over long distances.
- measurement errors and misinterpretations can occur if the relaxation time of the response signal to the test signal at a measurement electrode exceeds the time period of a measurement period.
- the control / evaluation unit signals that the target value has been reached; however, the supposed actual value is not an indication of exceeding a tolerable deposit formation, but is caused by the superimposition of different voltage values on the measuring electrode.
- the invention is based on the object of proposing a method and a device which is distinguished by reliable detection of the deposit formation in a magnetically inductive flow meter.
- the object is achieved in that a test pulse with a defined pulse duration is applied to the measuring electrode, that at least one response signal to the test pulse is determined at at least two measuring times, that the measuring times lie in a time window that is selected in such a way that that no foreseeable interference signals occur at the measuring electrode in this time window, that the relaxation time or the time until a predetermined discharge state of the measuring electrode is determined on the basis of the response signal determined in the measuring times, and that based on the determined relaxation time or based on the time until reaching a malfunction of the measuring electrode is recognized or recognizable due to the defined discharge state of the measuring electrode.
- the relaxation time or the time period for reaching the defined discharge state of the measuring electrode is determined and that determined relaxation time or the time period for reaching the defined discharge state of the measuring electrode is stored as a setpoint.
- An advantageous embodiment of the method according to the invention provides that the test pulse is applied to the measuring electrode with a predetermined or predeterminable pulse duration and / or with a predetermined or predeterminable pulse repetition frequency.
- the pulse duration of the test pulse and / or the pulse repetition frequency of the test pulses be predetermined or determined as a function of the conditions at the measurement location, in particular as a function of the measurement medium.
- a favorable embodiment of the method according to the invention provides that a change in the relaxation time or a change in the period of time until the defined discharge state of the measuring electrode is detected to determine whether the measuring electrode is working correctly or whether the measuring electrode is malfunctioning.
- a malfunction or an indication of an impending malfunction is displayed and / or output when the change in the relaxation time or the change in the time period until the defined discharge state of the measuring electrode is reached outside a tolerance range is around the target value or if the relaxation time or the time period until the defined discharge state of the measuring electrode tends to change.
- the time window is chosen such that it lies after the point in time at which the test pulse was applied to the measuring electrode to be checked, and before the point in time at which the magnetic field on the measuring electrode to be checked is switched. Within the time window described above, it is ensured that no changes in the potentials at the measuring electrodes occur due to a change in the magnetic field of the magnetic field arrangement.
- an automatic cleaning of the measuring electrode is activated as soon as a malfunction is displayed and / or output.
- a corresponding display and / or output is given, for example, that the measuring electrode is to be cleaned.
- the measuring electrode is automatically cleaned by applying a direct or alternating current.
- the object is achieved in that the evaluation / control unit determines at least one response signal to the test pulse at at least two measurement times, the measurement times being in a defined time window, the time window being selected such that no predictable times are given in this time window Interference signals occur at the measuring electrode, and that the control / evaluation unit determines the relaxation time or the period of time until a defined discharge state of the measuring electrode is reached on the basis of the response signal determined at the predetermined measuring times.
- test pulse is a rectangular pulse with a specific and / or predetermined pulse duration is regarded as particularly favorable.
- Fig. 3 a flow chart for controlling the control / evaluation unit.
- Fig. 1 shows a schematic representation of the device 1 according to the invention.
- the measuring tube 2 of a flow meter is likewise not separated from one flow through the medium shown in the direction of the measuring tube axis 10.
- the medium is at least to a small extent electrically conductive.
- the measuring tube 2 itself is made of a non-conductive material, or it is at least lined on its inside with a non-conductive material.
- charge carriers located in the medium migrate to the oppositely polarized measuring electrode 3; 4 from.
- the voltage building up between the two measuring electrodes 3, 4 is proportional to the flow velocity of the medium averaged over the cross-section of the measuring tube 2, ie it is a measure of the volume flow of the medium in the measuring tube 2.
- the measuring tube 2 is, incidentally, via connecting elements which in the drawing are not shown separately, connected to a pipe system through which the medium flows.
- the two measuring electrodes 3, 4 are in direct contact with the medium 2, as a result of which a coating 11, 12, which consists of particles of the medium, forms on the measuring electrodes 3, 4 in the course of time.
- This formation of deposits naturally influences the values of the induced voltage measured at the measuring electrodes 3, 4. If the covering is made of a non-conductive material, the flow meter no longer works at all.
- the measuring electrodes 3, 4 are connected to the control / evaluation unit 7 via connecting lines 5, 6.
- the control / evaluation unit 7 transmits a test pulse U p , in the simplest case a rectangular pulse, to the measuring electrodes 3, 4 via the connecting lines 5, 6.
- relaxation time ⁇ always means the time period until the response signal to the test signal (eg the rectangular pulse U p ) has reached a predetermined threshold value U i .
- the disadvantage of this known method is that the end of the relaxation time ⁇ can already lie in the subsequent measuring period in which the magnetic field and thus also the voltage at the measuring electrode 3, 4 have an opposite sign. This can result in the occurrence of a coating formation lying outside the tolerances, although in this case falling below a predetermined threshold value U t is the result of a corresponding one
- the setpoint value of the relaxation time ⁇ is incidentally determined as a function of the prevailing system and process conditions with measuring electrodes 3, 4 that are as clean as possible. Because of the dependence of the relaxation time ⁇ on the respective process and system conditions, it is very advantageous if the 'deposit formation detection' is calibrated in the process itself. This calibration is done e.g. B. by repeated application of test pulses (z. B. rectangular pulses U P ) of different lengths t p and subsequent preferably inventive determination of the relaxation time ⁇ . The pulse duration t P of the test pulse U p becomes so long changed until the relaxation time ⁇ is within a defined time window t END - t BEGIN .
- this time window t END - t BEGIN is selected in such a way that no foreseeable interference signals occur, as can be seen, for example, in the immediate vicinity of the switching times of the magnetic field.
- the determined pulse duration t p possibly the amplitude of the test signal U p and the associated relaxation time ⁇ are stored as target values.
- a test pulse U p in particular a rectangular pulse of the previously determined pulse duration t p, is applied to the measuring electrode 3, 4; a response signal to the test pulse U p is then determined at at least two measuring times t,, t 2 , the measuring times t ! , t 2 lie in a time window t END - t BEGJN , which is selected such that, as already mentioned several times - in this time window t Em - t BEGm there are no predictable interference signals at the
- Measuring electrode 3, 4 occur. Interference signals are caused in particular by switching the magnetic field.
- the time window t END - t BEGm is selected such that it lies between the reaching of the linear range of the detection of the voltage U at the measuring electrodes 3, 4 and the measuring time t END at the end of the measuring period.
- To determine the relaxation time ⁇ knowledge of two voltage values U x , U 2 at the measuring electrode 3, 4 is necessary.
- One can, for example, be identical to the test pulse U p , while the second is measured by measuring at a later measuring time t 2 , which lies within the time window t END - t BEGIN .
- t 2 becomes the relaxation time ⁇ or
- the measuring electrode 3, 4 is determined; on the basis of the determined relaxation time ⁇ or on the length of time until the defined discharge state U is reached, the measuring electrode 3, 4 a malfunction of the measuring electrode 3, 4, as is caused in particular by the formation of a deposit, is recognized or recognizable.
- the relaxation time ⁇ can be calculated using the following formula - reference being made to FIG. 2 for the nomenclature:
- the cleaning of the measuring electrodes 3, 4 or the indication that cleaning of the measuring electrodes 3, 4 is necessary can always take place when the deposit formation on the measuring electrodes 3, 4 becomes so strong that they lead to unacceptable falsifications of the Measured values on the measuring electrodes 3, 4 leads.
- FIG. 2 shows a representation of the relaxation behavior of the electrode potentials at the measuring electrodes 3, 4 with different deposits.
- a rectangular pulse U p of defined duration t p is applied to the measuring electrode 3; 4 given.
- the control / evaluation unit 7 calculates the relaxation time ⁇ on the basis of two different measuring times t. , t 2 measured voltage values. These measuring times t j , t 2 lie within a defined time window t END - t BEGm .
Landscapes
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Measuring Volume Flow (AREA)
Abstract
L'invention concerne un procédé magnétique-inductif de détermination du débit d'un agent s'écoulant dans un tube de mesure (2) dans la direction de l'axe du tube de mesure. Pour pouvoir détecter avec fiabilité la formation d'un dépôt sur une électrode de mesure, on applique une impulsion d'essai (Up) d'une durée (tp) définie à l'électrode de mesure (3, 4). On détermine au moins un signal réponse sur l'impulsion d'essai (Up) au niveau d'au moins deux points de mesure, les temps de mesure (t1, t2) étant situés dans un créneau temporel (tfin tdébut) choisi de telle façon que, dans ce créneau temporel (tfin tdébut), aucun signal parasite prévisible n'apparaisse sur l'électrode de mesure (3, 4). Le signal réponse déterminé aux temps de mesure (t1, t2) permet de déterminer le temps de relaxation (t) ou la durée jusqu'à l'obtention d'un état de décharge prédéterminé (Ui) de l'électrode de mesure (3, 4). Le temps de relaxation déterminé (t) ou le temps jusqu'à l'obtention de l'état de décharge défini (Ui) de l'électrode de mesure (3, 4) permet de reconnaître un dysfonctionnement de l'électrode de mesure (3, 4).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10335205A DE10335205A1 (de) | 2003-07-30 | 2003-07-30 | Verfahren zur magnetisch-induktiven Bestimmung der Durchflußrate eines Mediums |
PCT/EP2004/007976 WO2005012842A1 (fr) | 2003-07-30 | 2004-07-16 | Procede de determination magneto-inductive du debit d'un agent |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1649251A1 true EP1649251A1 (fr) | 2006-04-26 |
Family
ID=34072013
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04741101A Withdrawn EP1649251A1 (fr) | 2003-07-30 | 2004-07-16 | Procede de determination magneto-inductive du debit d'un agent |
Country Status (5)
Country | Link |
---|---|
US (1) | US7340963B2 (fr) |
EP (1) | EP1649251A1 (fr) |
CN (1) | CN100420920C (fr) |
DE (1) | DE10335205A1 (fr) |
WO (1) | WO2005012842A1 (fr) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102004046238A1 (de) * | 2004-09-22 | 2006-03-23 | Endress + Hauser Flowtec Ag | Magnetisch-induktives Durchflussmessgerät |
US7260486B2 (en) | 2004-09-22 | 2007-08-21 | Endress + Hauser Flowtec Ag | Method for operating and/or reviewing a magneto-inductive flow meter |
DE102007014469A1 (de) * | 2007-03-22 | 2008-09-25 | Endress + Hauser Flowtec Ag | Verfahren zur vorausschauenden Wartung und/oder Verfahren zur Bestimmung der elektrischen Leitfähigkeit bei einem magnetischinduktiven Durchflussmessgerät |
EP3317617B1 (fr) * | 2015-06-30 | 2020-06-17 | Micro Motion Inc. | Débitmètre magnétique avec autonettoyage in situ automatique |
NO20190208A1 (en) * | 2019-02-14 | 2020-08-17 | Roxar Flow Measurement As | Impedance layer estimation |
CN110332964B (zh) * | 2019-07-06 | 2020-08-04 | 杭州乾博科技有限公司 | 一种可检测故障的线圈感应式水表 |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4409846A (en) * | 1979-02-08 | 1983-10-18 | Aichi Tokei Denki Co., Ltd. | Electromagnetic flow meter |
US4468608A (en) * | 1981-12-11 | 1984-08-28 | Instrumentation Laboratory Inc. | Electrochemical sensor instrumentation |
JPS5960318A (ja) * | 1982-09-30 | 1984-04-06 | Toshiba Corp | 電磁流量計 |
JPS59122914A (ja) * | 1982-12-28 | 1984-07-16 | Toshiba Corp | 電磁流量計 |
JPS61204521A (ja) | 1985-03-08 | 1986-09-10 | Hitachi Ltd | 電磁流量計 |
JPH01288724A (ja) * | 1988-05-17 | 1989-11-21 | Toshiba Corp | 電磁流量計の電極汚れ検知装置 |
DE4122225A1 (de) * | 1991-07-04 | 1993-01-07 | Fischer & Porter Gmbh | Schaltungsanordnung zur ermittlung von fehlern in einer magnetisch-induktiven durchflussmessanordnung |
US6014902A (en) * | 1995-12-28 | 2000-01-18 | The Foxboro Company | Magnetic flowmeter with diagnostics |
GB2348012B (en) * | 1996-01-17 | 2000-12-06 | Abb Instrumentation Ltd | Calibration of flow meters |
EP1108989B1 (fr) * | 1999-12-15 | 2007-01-24 | Endress + Hauser Flowtec AG | Dispositif pour la mesure d'un débit d'un fluide de mesure dans un conduit de mesure |
EP1108988A1 (fr) * | 1999-12-15 | 2001-06-20 | Endress + Hauser Flowtec AG | Procédé et dispositif pour la détermination d'un débit d'un fluide dans un conduit de mesure |
JP3915459B2 (ja) * | 2001-09-20 | 2007-05-16 | 横河電機株式会社 | 電磁流量計 |
-
2003
- 2003-07-30 DE DE10335205A patent/DE10335205A1/de not_active Withdrawn
-
2004
- 2004-07-16 CN CNB2004800216551A patent/CN100420920C/zh not_active Expired - Fee Related
- 2004-07-16 WO PCT/EP2004/007976 patent/WO2005012842A1/fr active Application Filing
- 2004-07-16 US US10/566,388 patent/US7340963B2/en not_active Expired - Fee Related
- 2004-07-16 EP EP04741101A patent/EP1649251A1/fr not_active Withdrawn
Non-Patent Citations (1)
Title |
---|
See references of WO2005012842A1 * |
Also Published As
Publication number | Publication date |
---|---|
DE10335205A1 (de) | 2005-02-17 |
US7340963B2 (en) | 2008-03-11 |
CN1829901A (zh) | 2006-09-06 |
WO2005012842A1 (fr) | 2005-02-10 |
CN100420920C (zh) | 2008-09-24 |
US20070143041A1 (en) | 2007-06-21 |
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