EP1405045A1 - Dispositif et procede pour determiner le debit d'un milieu - Google Patents

Dispositif et procede pour determiner le debit d'un milieu

Info

Publication number
EP1405045A1
EP1405045A1 EP02747392A EP02747392A EP1405045A1 EP 1405045 A1 EP1405045 A1 EP 1405045A1 EP 02747392 A EP02747392 A EP 02747392A EP 02747392 A EP02747392 A EP 02747392A EP 1405045 A1 EP1405045 A1 EP 1405045A1
Authority
EP
European Patent Office
Prior art keywords
measuring
control
charge
evaluation unit
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Withdrawn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
EP02747392A
Other languages
German (de)
English (en)
Inventor
Thomas Budmiger
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
Priority to EP02747392A priority Critical patent/EP1405045A1/fr
Publication of EP1405045A1 publication Critical patent/EP1405045A1/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Withdrawn legal-status Critical Current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
    • G01F1/60—Circuits 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
    • G01F1/588—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

Definitions

  • the invention relates to a device for measuring the flow of a medium which flows through a measuring tube in the direction of the measuring tube axis, with a magnet arrangement which is periodically switched over and which generates a magnetic field which passes through the measuring tube and runs essentially transversely to the measuring tube axis a measuring electrode arrangement which supplies a measuring signal dependent on the flow rate of the medium through the measuring tube, and with a control / evaluation unit which determines the flow rate of the medium in the measuring tube on the basis of the measuring signal. Furthermore, the invention relates to a method for determining the flow of a medium through a measuring tube.
  • the voltage difference across the measuring electrodes is measured to determine the flow rate.
  • the electrically conductive, metal measuring electrodes are in direct contact with the medium.
  • a boundary layer capacitance is formed on the surface of the measuring electrodes between the metal of the measuring electrodes and the medium.
  • This boundary layer capacity is charged on the one hand by electrochemical processes and on the other hand by interferences from transient processes.
  • the transient processes are, for example, changes in the voltage across the coils of the magnet system or changes in the magnetic field.
  • the boundary layer capacities are charged to potentials that can be of the order of one volt.
  • the potentials tapped at the two measuring electrodes can be different.
  • the differences are in the order of 100 mV.
  • the position of the zero point, the zero point representing the measurement signal when the medium is stationary, changes as a result of different interferences from transient processes in the two measurement electrode paths. Due to the different boundary layer capacitances on the measuring electrodes, the stray effects have different effects on the potentials measured on the measuring electrodes.
  • the aforementioned problems can be reduced considerably if the potentials on the measuring electrodes are influenced in a targeted and controlled manner.
  • the potentials at the measuring electrodes are preferably, but not necessarily, reduced to the lowest possible value, that is to say as far as possible to zero. In this context, care must of course be taken that the measurement signals and thus the flow information obtained via the measurement electrodes remain / remain unaffected as far as possible.
  • the invention has for its object to improve the metrological properties of a magnetic-inductive flow meter or to provide a method with which the metrological properties of a magnetic-inductive flow meter are improved.
  • the object is achieved in that the evaluation / control unit compensates for an interference potential at the measuring electrode arrangement by applying a charge of opposite sign to the measuring electrode arrangement, which charge is approximately the same size as the charge resulting from of the interference potential is stored in a boundary layer capacitance on the measuring electrode arrangement.
  • control / evaluation unit deviates the charge stored on the measuring electrode arrangement in a boundary layer capacity by the application of a charge with the opposite sign to the value zero or to a constant zero. regulates the value.
  • each measuring electrode is assigned a control circuit which is controlled by the control / evaluation unit.
  • each control circuit is activated or deactivated by actuating an analog switch.
  • the control circuit is preferably activated shortly before the direction of the magnetic field generated by the magnetic field arrangement is changed or during the switching process of the magnetic field.
  • the control / evaluation unit additionally places the measuring electrodes on a reference potential during the switching process, i.e. a short circuit to the reference potential is carried out.
  • a further analog switch is preferably provided in each case. By actuating this switch, the control / evaluation unit sets the measuring electrodes to ground during a switching process of the magnetic field.
  • a further embodiment of the device according to the invention provides that the control / evaluation unit determines the potentials on the measuring electrodes, forms the average over an even number of measuring periods and evaluates the average as the average potential; the control / evaluation unit then regulates the average potential by applying charge pulses to approximately the value zero or a value slightly different from zero.
  • the control preferably takes place during the switching of the direction of the magnetic field. As a result, the transients caused by the switching process are suppressed at the same time; this improves the deviation of the measurement result from zero when the medium is at a standstill.
  • the method used in connection with this embodiment corresponds the method described in the unpublished EP 01116432.4. The present invention enjoys the priority of EP 01116432.4.
  • control / evaluation unit discharges a charge, which is stored in a boundary layer capacitance on the measuring electrode arrangement as a result of an interference potential, to ground at certain time intervals.
  • This second variant of the device according to the invention can be implemented particularly easily via at least one switch in each case.
  • a switch is provided between an output of the control / evaluation unit and the input of the associated measuring electrode.
  • the control / evaluation unit puts the measuring electrodes shortly before or during a switching process of the magnetic field for a short period of time by operating the switches.
  • an interference potential occurring at the measuring electrode arrangement is compensated for by charging the measuring electrode arrangement with a charge of the opposite sign, the charge being approximately the same size as the charge resulting of the interference potential is stored in a boundary layer capacitance on the measuring electrode arrangement.
  • An alternative solution provides that a charge, which is stored in a boundary layer capacitance on the measuring electrode arrangement as a result of an interference potential, is discharged to ground at certain time intervals.
  • Fig. 1 a block diagram of a first variant of the device according to the invention or a first device for performing the method according to the invention.
  • 2 shows a block diagram of a second variant of the device according to the invention or a second device for carrying out the method according to the invention and
  • FIG. 3 shows a block diagram of a third variant of the device according to the invention or a third device for carrying out the method according to the invention.
  • the magnetic inductive sensor comprises a measuring tube 5, a magnet arrangement, not shown separately, two preferably opposite measuring electrodes 2, 3 and a control circuit 11, 12 assigned to each measuring electrode 2, 3. Furthermore, a ground electrode 4 is arranged in the lower part of the measuring tube 5. In the case shown, the ground electrode 4 is designed in the same way as the measuring electrodes 2, 3. However, it can be implemented in the form of an earthing ring, e.g. is clamped between a flange of the measuring tube and a counter flange of the pipeline.
  • the medium 14 to be measured flows through the measuring tube 5.
  • the measuring tube 5 is made of metal, it is provided on the inside with an electrically non-conductive layer.
  • the measuring electrodes 2, 3 are designed as galvanic electrodes; they come into direct contact with the medium. Of course, capacitive electrodes can also be used in connection with the present invention.
  • An electrical voltage to ground is tapped at each of the measuring electrodes 2, 3. According to Faraday's law, the voltage prevailing between the two measuring electrodes 2, 3 is proportional to the flow velocity of the medium 14 in the measuring tube 5.
  • a measurement signal representing the flow rate through the measuring tube 5 is passed on to the control / evaluation unit 7 via the resistor 8 and the amplifier 9 designed as a voltage follower; the control / evaluation unit 7 uses the measurement signals to determine the volume flow of the medium 13 through the measuring tube 5.
  • the control / evaluation unit 7 closes for a predetermined one Time period switches S1, S3 and thus activates the control circuits 11, 12.
  • the control circuits 11, 12 regulate the interference potential at the measuring electrodes 2, 3 to the value zero or to any predetermined value.
  • FIG. 2 shows a block diagram of a second variant of the device according to the invention or of a second device for carrying out the method according to the invention.
  • the device shown in FIG. 2 has a very simple structure and can therefore be implemented very inexpensively.
  • the measurement signals which provide information about the volume flow of the medium 13 through the measuring tube 5, are forwarded to the control / evaluation unit 7.
  • the provision and transmission of the measurement signals is known and is no longer shown separately in FIG. 2.
  • the two analog switches S2, S4 are connected to ground for a predetermined period of time. As a result, excess charges or charge deficits at the measuring electrodes 2, 3 are compensated for.
  • FIG. 3 shows a block diagram of a third variant of the device according to the invention or a third device for carrying out the method according to the invention.
  • This embodiment represents a combination of the embodiments shown in FIGS. 1 and 2. It is preferably used when the control process or the compensation takes place at a different time than during the switching process of the magnetic field.
  • the measuring electrodes 2, 3 are connected to the reference potential during the switching process, ie the measuring electrodes 2, 3 are short-circuited.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

La présente invention concerne un débitmètre d'induction magnétique dans lequel une unité d'analyse/régulation (7) compense un potentiel parasite au niveau du dispositif à électrode de mesure (2, 3) en soumettant ce dispositif à une charge de signe opposé, qui est approximativement égale à la charge stockée dans un condensateur de couche limite au niveau du dispositif à électrode de mesure (2, 3) en raison du potentiel parasite. Alternativement, l'unité d'analyse/régulation (7) dérive, à des intervalles de temps donnés par rapport à la masse, une charge qui est stockée dans un condensateur de couche limite au niveau du dispositif à électrode de mesure (2, 3) en raison du potentiel parasite.
EP02747392A 2001-07-06 2002-06-15 Dispositif et procede pour determiner le debit d'un milieu Withdrawn EP1405045A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP02747392A EP1405045A1 (fr) 2001-07-06 2002-06-15 Dispositif et procede pour determiner le debit d'un milieu

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP01116432A EP1273891A1 (fr) 2001-07-06 2001-07-06 Procédé d'alimentation d'un débitmètre électromagnétique
EP01116432 2001-07-06
EP02747392A EP1405045A1 (fr) 2001-07-06 2002-06-15 Dispositif et procede pour determiner le debit d'un milieu
PCT/EP2002/006612 WO2003004977A1 (fr) 2001-07-06 2002-06-15 Dispositif et procede pour determiner le debit d'un milieu

Publications (1)

Publication Number Publication Date
EP1405045A1 true EP1405045A1 (fr) 2004-04-07

Family

ID=8177965

Family Applications (2)

Application Number Title Priority Date Filing Date
EP01116432A Withdrawn EP1273891A1 (fr) 2001-07-06 2001-07-06 Procédé d'alimentation d'un débitmètre électromagnétique
EP02747392A Withdrawn EP1405045A1 (fr) 2001-07-06 2002-06-15 Dispositif et procede pour determiner le debit d'un milieu

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP01116432A Withdrawn EP1273891A1 (fr) 2001-07-06 2001-07-06 Procédé d'alimentation d'un débitmètre électromagnétique

Country Status (2)

Country Link
EP (2) EP1273891A1 (fr)
WO (1) WO2003004977A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040126349A1 (en) 2002-12-31 2004-07-01 Anderson Glen T. Hair and scalp compositions with a crosslinked silicone elastomer and method of using same
DE102004046238A1 (de) 2004-09-22 2006-03-23 Endress + Hauser Flowtec Ag Magnetisch-induktives Durchflussmessgerät
DE102007015368A1 (de) 2007-03-28 2008-10-02 Endress + Hauser Flowtec Ag Verfahren zum Betreiben eines magnetisch-induktiven Durchflußmeßgeräts

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5679911A (en) * 1979-12-05 1981-06-30 Hitachi Ltd Electromagnetic flowmeter
DE3537752A1 (de) * 1985-10-23 1987-04-23 Flowtec Ag Verfahren zur kompensation von stoerspannungen im elektrodenkreis bei der magnetisch-induktiven durchflussmessung
JP3602636B2 (ja) * 1996-02-26 2004-12-15 愛知時計電機株式会社 電磁流量計
JP3453751B2 (ja) * 1996-12-10 2003-10-06 横河電機株式会社 電磁流量計
JPH10213466A (ja) * 1997-01-28 1998-08-11 Yokogawa Electric Corp 電磁流量計
US5866823A (en) * 1997-05-13 1999-02-02 Hersey Measurement Company Commutating electrode magnetic flowmeter

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO03004977A1 *

Also Published As

Publication number Publication date
EP1273891A1 (fr) 2003-01-08
WO2003004977A1 (fr) 2003-01-16

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