EP1728052A2 - Dispositif destine a mesurer et/ou surveiller le debit d'un milieu de mesure - Google Patents

Dispositif destine a mesurer et/ou surveiller le debit d'un milieu de mesure

Info

Publication number
EP1728052A2
EP1728052A2 EP05740174A EP05740174A EP1728052A2 EP 1728052 A2 EP1728052 A2 EP 1728052A2 EP 05740174 A EP05740174 A EP 05740174A EP 05740174 A EP05740174 A EP 05740174A EP 1728052 A2 EP1728052 A2 EP 1728052A2
Authority
EP
European Patent Office
Prior art keywords
electrode
cables
measuring
electrode lines
measuring tube
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Withdrawn
Application number
EP05740174A
Other languages
German (de)
English (en)
Inventor
Günther Bähr
Fred Kappertz
Thomas KÜNG
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Endress and Hauser Flowtec AG
Original Assignee
Endress and Hauser Flowtec AG
Flowtec AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Endress and Hauser Flowtec AG, Flowtec AG filed Critical Endress and Hauser Flowtec AG
Publication of EP1728052A2 publication Critical patent/EP1728052A2/fr
Withdrawn legal-status Critical Current

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
    • G01F1/588—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 combined constructions of electrodes, coils or magnetic circuits, accessories therefor
    • 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

Definitions

  • the invention relates to a device for measuring and / or monitoring the flow of a measuring medium which flows through a measuring tube in the direction of the longitudinal axis of the measuring tube, with a magnet arrangement consisting of a coil arrangement and at least two pole pieces, which are arranged so that they generate a magnetic field which penetrates the measuring tube and runs essentially transversely to the longitudinal axis of the measuring tube, with two measuring electrodes which are galvanically or capacitively coupled to the measuring medium and arranged in such a way that a measuring voltage caused by the measuring medium is induced therein, and with an evaluation / Control unit, which provides information about the volume flow of the measuring medium in the measuring tube based on the measuring voltage induced in the measuring electrode, wherein a first electrode cable or a first electrode line and a second electrode cable or a second electrode line are provided, via which the measurement signals between the both measuring electrodes and the control / evaluation unit.
  • Magnetic-inductive flowmeters use the principle of electrodynamic induction for volumetric flow measurement: Charge carriers of the measuring medium that move perpendicular to a magnetic field induce an induction voltage in measuring electrodes that are also arranged essentially perpendicular to the direction of flow of the measuring medium. This voltage induced in the measuring electrodes is proportional to the flow velocity of the measuring medium averaged over the cross section of the tube; it is therefore proportional to the volume flow.
  • the measurement signals which are tapped at the measurement electrodes are conducted via electrode cables to the converter, which contains, among other things, a control / evaluation unit.
  • the electrode cables are mostly guided along opposite side surfaces of the pole piece of the magnet arrangement. Since the between the If the area covered by the electrode cables is to be as small as possible in order to avoid induction voltages, the electrode cables are brought together in the area of the pole piece. This merging requires a change of direction, the critical area spanned between the electrode cables in the corresponding area not being oriented exclusively parallel to the main direction of the magnetic field.
  • Corresponding cable guides are known from electromagnetic flowmeters. There is an increased risk here that, particularly during changes in the magnetic field, interference voltages are induced in the electrode cables, which can impair the measuring accuracy.
  • the invention has for its object to improve the measurement accuracy of a magnetic-inductive flow meter.
  • the electrode cables or the electrode lines are guided substantially symmetrically to a partial area of the measuring tube and to the two pole pieces, a first partial area being defined in which the two electrode cables or the two electrode lines in The outer area of the measuring tube and the pole piece extend, a third partial area being defined in which the two electrode cables or electrode lines run parallel to one another, and a second partial area is provided between the first partial area and the third partial area, in which the two electrode cables or the electrode lines are arranged in such a way that a critical area is defined between them, which is oriented essentially perpendicular to the main direction of the magnetic field of the magnet arrangement, and that the electrode cables or the electrode lines are designed and / or wired in the area of the defined area are that interference voltages that are induced in the electrode cables or in the electrode lines are at least approximately compensated for.
  • the compensation of interference voltages is carried out specifically in the area of the greatest concentration of the magnetic field, that is to say in the area of the pole pieces. This allows the expansion of the Minimize the critical area between the lines.
  • care is taken that the two electrode cables or electrode lines are routed as closely as possible.
  • the shortening of the stabilization time makes it possible to either increase the measuring rate or to extend the integration time with the same measuring rate. A shorter measurement time corresponds to a faster sampling of the measurement signal; this improves the measuring performance of the magnetic inductive flow meter for processes with high dynamics.
  • a longer integration time (this runs after the magnetic field has been switched over from the point in time at which the magnetic field has assumed a sufficiently stable value) improves the relationship between measuring time and dead time.
  • Dead time identifies the time range in a measurement period that is not recorded for the measurement value acquisition.
  • the first electrode cable has a branch with two line branches, the first line branch being oriented essentially in the opposite direction of rotation around the critical surface in the opposite direction of rotation.
  • the one line branch of one of the two electrode cables is preferably designed and arranged in such a way that the critical magnetic field which causes the disturbance passes through the area defined by the line branch (for example guided by one of the pole pieces).
  • an advantageous embodiment of the device according to the invention proposes that the two line branches of the electrode cable each have a defined resistance.
  • an embodiment of the device according to the invention provides that the resistors are nominally constant and that the resistance ratio of the resistors is dependent on the particular arrangement and configuration of the two line branches and on the arrangement and configuration of the second electrode cable.
  • the ability to pre-calculate the resistance values eliminates the need to adjust each flow meter manufactured during the production process. As a result, the manufacturing time is reduced, which is reflected in a reduction in manufacturing costs.
  • Noteworthy in the aforementioned embodiment is the fact that the voltages induced due to the design of the electrode cable in the electrode cable, which are largely caused by the time-varying magnetic field of the magnet arrangement, can be essentially compensated with nominally constant current dividing resistors ,
  • the two electrode cables or the two electrode lines are arranged in the first partial area essentially mirror-symmetrically to a plane which is spanned by the longitudinal axis of the measuring tube and the connecting axis that connects the coils of the magnet arrangement.
  • the two electrode cables or the two electrode lines are ideally arranged in the first partial area in the plane through the longitudinal axis of the measuring tube and the connecting axis that connects the electrodes of the magnet arrangement, is spanned.
  • the magnet arrangement consists of two pole pieces, which are arranged on both sides of the measuring tube and are surrounded by a coil.
  • the coil arrangement is shown schematically in FIG. 3.
  • the electrode cable or the two electrode lines in the area of the critical area on a carrier material preferably on a flexible carrier material, e.g. are arranged on a so-called flexprint or a print.
  • FIG. 1 a schematic representation of a magnetic-inductive flow meter
  • 2 shows a perspective illustration of a routing of the electrode cables known from the prior art between the measuring electrodes and the converter in a magnetic-inductive flow meter
  • FIG. 2a shows a plan view of the plane which is marked with A in 2 is marked
  • FIG. 2b the electrode circuit with signal and interference voltages in the area of the defined area when the electrode cable is shown in FIG. 2
  • FIG. 3 a perspective view of the guide according to the invention Electrode cable between the measuring electrodes and the converter in a magnetic-inductive flow meter
  • FIG. 3 a a plan view of the defined plane according to the marking B in FIG. 3, [0022] FIG.
  • Fig. 1 shows a schematic representation of a magnetic-inductive flow meter 1, as is known from the prior art.
  • the measuring tube 2 of the flow measuring device is flowed through by a measuring medium, likewise not shown separately, in the direction of the measuring tube axis 10.
  • the measuring 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.
  • the measuring electrodes 3, 4 are connected to the control / evaluation unit 7 via the signal lines 5, 6. Measurement data can also be forwarded to the display unit 8 via the connecting line 9.
  • the pole piece 12 preferably consists of a plurality of composite pole piece lamellae 13. The layered structure of the pole piece 12 suppresses eddy currents.
  • the electrode cables 5, 6 show a changed direction course. This is clearly visible in FIG. 2a, which shows a top view of the pole shoe 12 in the plane of the defined surface 14.
  • the area 14 spanned between the two electrode cables 5, 6 in this area is oriented essentially perpendicular to the magnetic field which changes over time due to the principle and which is generated by the magnet arrangement. In this area, the risk of induction currents being induced in the electrode cables 5, 6 due to interference voltages is particularly great. It is necessary to guide the electrode cables 5, 6 as described above, since this allows the area spanned between the electrode cables 5, 6 to be designed to be minimal.
  • 2b shows an equivalent circuit diagram for the voltages when the electrode cables 5, 6 are shown in FIG. 2.
  • the voltage in the electrode cables 5, 6 can be easily determined on the basis of the following assumptions: - A homogeneous magnetic induction prevails in the pole shoe 12 - The electrode cables 5, 6 are guided symmetrically - Each electrode cable 5, 6 circles the pole shoe 12 in a Vi-rounding - The magnetic field shows no scatter.
  • the corresponding formulas are:
  • U c is the total voltage in the measuring electrode circuit. characterizes the interference voltage in each of the two electrode cables 5; 6 is induced.
  • U s is the voltage which is tapped at the measuring electrodes 3, 4 and which is composed of the voltage present at the measuring electrodes 3, 4 and the voltage which is attributable to the flowing measuring medium 11. It can be seen from the above formula that the interference voltages V v that are shown during the switching of the magnetic field add up. These drop with a time constant that depends on the electrode circuit (and possibly also on the measuring medium).
  • Fig. 3 shows a perspective view of the inventive routing of the electrode cables 5, 6 between the measuring electrodes 3, 4 and the converter in a magnetic-inductive flow meter 1.
  • Fig. 3a is a plan view of the plane 14 according to the label B. seen in Fig. 3.
  • the one electrode cable 5 has a branch 17 with two line branches 18, 19, one line branch 18 being oriented opposite to the other line branch 19 (opposite direction of rotation around the spanned surface).
  • the line branch 19 of the electrode cable 5 is designed and arranged in such a way that the pole piece 12 of the magnet arrangement lies within the surface 14 which is defined by the line branch 19.
  • At least one resistor R1, R2 is installed in each of the two line branches 18, 19 of the electrode cable 5.
  • the resistors R1, R2 are nominally constant and the resistance ratio of the two resistors R1, R2 in the two line branches 18, 19 depends on the respective arrangement and configuration of the two line branches 18, 19 and on the arrangement and configuration of the second electrode cable 6.
  • the possibility of pre-calculating the resistance values R1, R2 eliminates the need to compare each flowmeter 1 manufactured during the production process. As a result, the manufacturing time is reduced, which is reflected in a reduction in manufacturing costs.
  • 3b shows an equivalent circuit diagram for the voltage conditions in the measuring electrode circuit.
  • the interference voltage which is induced in the area 14 of the electrode cable 5 is:
  • the interference voltages in the area of the area 14 are compensated for when the two resistors R1, R2 in the line branches 18, 19 are the same.
  • the significant advantage of the solution according to the invention can be seen in the fact that the resistance values R1, R2 can be calculated in advance, so that no individual adjustment is necessary during production.

Abstract

L'invention concerne un débitmètre à induction magnétique. L'objectif de cette invention est d'augmenter la précision de mesure de ce débitmètre à induction magnétique. A cet effet, les câbles (5, 6), ou lignes, d'électrodes sont guidés de façon sensiblement symétrique à une zone partielle du tube de mesure (2) et aux deux pièces polaires (12) ; une première zone partielle (20), dans laquelle les deux câbles (5, 6), ou lignes, d'électrodes s'étendent dans la zone extérieure du tube de mesure (2) et de la pièce polaire (12), est définie ; une troisième zone partielle (21), dans laquelle les deux câbles (5, 6), ou lignes, d'électrodes s'étendent parallèlement l'un ou l'une par rapport à l'autre, est définie et une deuxième zone partielle (22) est située entre la première zone partielle (20) et la troisième zone partielle (21), deuxième zone partielle dans laquelle les deux câbles (5, 6), ou lignes, d'électrodes sont agencés, de sorte qu'une surface critique (14), orientée de façon sensiblement perpendiculaire à la direction principale du champ magnétique de l'ensemble magnétique, est définie entre eux, ces câbles (5, 6), ou lignes, d'électrodes étant placés et/ou connectés dans la zone de la surface (14) définie, de sorte que des tensions parasites induites dans les câbles (5, 6), ou lignes, d'électrodes sont au moins approximativement compensées.
EP05740174A 2004-03-22 2005-03-22 Dispositif destine a mesurer et/ou surveiller le debit d'un milieu de mesure Withdrawn EP1728052A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE200410014295 DE102004014295A1 (de) 2004-03-22 2004-03-22 Vorrichtung zum Messen und/oder Überwachen des Durchflusses eines Messmediums
PCT/EP2005/051314 WO2005090927A2 (fr) 2004-03-22 2005-03-22 Dispositif destine a mesurer et/ou surveiller le debit d'un milieu de mesure

Publications (1)

Publication Number Publication Date
EP1728052A2 true EP1728052A2 (fr) 2006-12-06

Family

ID=34980725

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05740174A Withdrawn EP1728052A2 (fr) 2004-03-22 2005-03-22 Dispositif destine a mesurer et/ou surveiller le debit d'un milieu de mesure

Country Status (3)

Country Link
EP (1) EP1728052A2 (fr)
DE (1) DE102004014295A1 (fr)
WO (1) WO2005090927A2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102012016408B4 (de) 2012-08-21 2022-06-09 Krohne Ag Magnetisch-induktives Durchflussmessgerät mit einer Mehrzahl von Funktionseinheiten, konstruktive Realisierung
DE202014103426U1 (de) * 2014-07-25 2014-08-04 Endress + Hauser Flowtec Ag Magnetisch-induktives Durchflussmessgerät

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5433747B2 (fr) * 1974-06-28 1979-10-23
JPS569656B2 (fr) * 1974-10-30 1981-03-03
US4106337A (en) * 1976-05-19 1978-08-15 Sybron Corporation Magnetic flow meter nulling system
US4428241A (en) * 1981-11-06 1984-01-31 Fischer & Porter Company Electrode wiring harness for magnetic flowmeter
DE4100987A1 (de) * 1991-01-15 1992-07-23 Ketelsen Broder Einrichtung zur induktiven messung des zustandes eines stromes elektrisch leitfaehiger fluessigkeit
DE19535997C2 (de) * 1995-09-27 1997-09-25 Ketelsen Broder Induktiver Durchflußmesser

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2005090927A3 *

Also Published As

Publication number Publication date
DE102004014295A1 (de) 2005-10-06
WO2005090927A3 (fr) 2006-01-12
WO2005090927A2 (fr) 2005-09-29

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