EP2844960A1 - Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu - Google Patents

Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu

Info

Publication number
EP2844960A1
EP2844960A1 EP13719549.1A EP13719549A EP2844960A1 EP 2844960 A1 EP2844960 A1 EP 2844960A1 EP 13719549 A EP13719549 A EP 13719549A EP 2844960 A1 EP2844960 A1 EP 2844960A1
Authority
EP
European Patent Office
Prior art keywords
electrodes
measuring device
period
switch
flow rate
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Withdrawn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
EP13719549.1A
Other languages
German (de)
English (en)
Inventor
Marcus Wolff
Henry BRUHNS
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.)
Zylum Beteiligungs GmbH and Co Patente II KG
Original Assignee
Zylum Beteiligungs GmbH and Co Patente II KG
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
Priority claimed from PCT/EP2012/057939 external-priority patent/WO2013164011A1/fr
Application filed by Zylum Beteiligungs GmbH and Co Patente II KG filed Critical Zylum Beteiligungs GmbH and Co Patente II KG
Priority to EP13719549.1A priority Critical patent/EP2844960A1/fr
Publication of EP2844960A1 publication Critical patent/EP2844960A1/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Withdrawn legal-status Critical Current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 present invention relates to a measuring device for measuring the
  • Flow rate of an electrically conductive medium in a volume penetrated by a magnetic field comprising means for generating the magnetic field, at least two electrodes and an evaluation unit which evaluates a signal of the electrodes and calculates the flow rate.
  • the invention also relates to a method for measuring the
  • Magnetic-inductive flowmeters typically have a measuring tube through which the electrically conductive medium flows
  • the at least two electrodes are typically disposed on opposite sides of the measuring tube and measure a voltage which, in the ideal case, is proportional to the flow velocity of the charge carriers, i. H. to the flow rate of the electrically conductive medium.
  • Such methods require only a very low electrical conductivity, so z. B. also the
  • Flow rate of tap water can be determined.
  • the decoupling of the signal to be measured can be done either galvanic or capacitive.
  • a galvanic decoupling the electrodes are in electrical contact with the medium.
  • the electrodes are in electrical contact with the medium.
  • the electrodes are formed as large-area plates of a capacitor and are located on the outside of the tube, so are not in contact with the medium.
  • the measuring devices of this type typically used today use electromagnetic alternating fields generated by electromagnets to generate the required magnetic field. This leads to the induction of interference voltages at the electrodes. These must be specifically suppressed by filters. For a simple and energy-efficient operation, it would thus be desirable to replace the electromagnets operated with alternating voltage by permanent magnets with a static magnetic field. When using permanent magnets, however, additional measurement errors are observed, which represent a drift of the induced voltage measured at the electrodes. This drift is a random DC voltage value that varies over time and is superimposed on the actual, induced measured value. This measurement error can be caused by electrostatic or electrochemical charges. Such measurement errors can not be excluded by statistical methods.
  • the object is achieved in that the at least two electrodes of the measuring device are connected to a switch which is designed to short-circuit the electrodes.
  • the object is achieved by a method of the type mentioned, in which the electrodes are short-circuited during a first period, in particular a period between 0.3 and 1 seconds, the short circuit during a second period, in particular one Period between 1 and 3 seconds, is opened, a useful signal is read from the electrodes and the flow rate is calculated based on the read-out useful signal.
  • the said electrostatic and electrochemical charges occur at the electrodes of the measuring device, in particular near their surfaces.
  • the charges but degraded (neutralized) by the switch shorts the electrodes and enforces a potential equalization in this way. If you then cancel this short circuit again, it can be assumed that a resulting immediately after this switching operation
  • electrochemical and electrostatic processes cause no measurement error, since they act more slowly and slowly rebuild after opening the short circuit. It does not matter whether the signal extraction works according to the galvanic or capacitive principle.
  • the evaluation of the signal measured after opening the short circuit can be carried out using the methods known from the prior art.
  • the switch is a
  • electronic switch In contrast to mechanical switches (eg relays), electronic switches are characterized by lower energy consumption, longer service life, short switching times and low leakage currents.
  • the switches to be used according to the invention are always either in the open or in the closed train position, with a very short change-over phase due to technical reasons only. In other embodiments of the invention, however, provision can also be made for a targeted transition to take place between the locked closed state.
  • the means for generating the magnetic field is a permanent magnet.
  • the switch comprises at least one
  • MOSFET preferably a MOSFET, in particular a MOSFET in a CMOS IC.
  • MOSFETs are characterized by short switching times and low
  • the switch in the open state has a resistance of at least 10 GOhm, in particular at least 100 GOhm. Since the measurement of the signal in the open state of the switch, but the switch is still connected to the electrodes, the signal of the electrodes should not be falsified or weakened by too low a resistance of the open switch.
  • the measuring device has a drive unit for the switch, wherein the drive unit comprises at least one timer.
  • the switch automatically, z. B. at regular intervals, closed and opened.
  • the timer can itself specify predetermined time intervals between closing and opening the switch.
  • the time given by the switch could also depend on variable values, e.g. B.
  • the timer could be shorter at high measured flow rates
  • the control unit can also specify when the evaluation of signals from the electrodes takes place.
  • the timer can also specify a periodic sequence of switch activation and signal evaluation.
  • control unit is designed such that the switch for the duration of a first period, in particular a period between 0.3 and 1 seconds, is closed and for the duration of a second period, in particular a period between 1 and 3 seconds, is opened, further wherein the evaluation unit is designed such that the signal of the electrodes is evaluated immediately after the second period.
  • the electrodes are short-circuited for each 50 to 100 ms, in particular approximately 80 ms, and then for 10 to 50 ms,
  • the electrodes can be short-circuited again and the described process can be repeated periodically. In this way, the induced voltage can be measured time-discretely.
  • the continuous storage of many discrete measured values enables a mathematical post-treatment to suppress statistical measurement errors (eg digital filtering or mean value calculation).
  • first period depends on the time required for the electrostatic and electrochemical charges to be sufficiently degraded. This can depend on several factors, eg. Example of the geometry of the measuring device, the nature of the flowing medium, the flow rate of the medium and the material and the surface of the electrodes. Accordingly, in other embodiments of the invention also significantly shorter or longer periods may be provided. In particular, first time periods between 100 and 300 milliseconds or first time periods between 1 and 10 seconds would be conceivable.
  • the duration of the second period should be chosen so that the
  • Settling time of the measuring circuit is essentially comprises. Since very different capacitances of the measuring circuit and thus very different settling times are also conceivable here, depending on the configuration of the measuring circuit, different values are also possible for the duration of the second period in different embodiments of the invention, in particular periods between 100 milliseconds and 1 second or periods between 3 and 10 seconds. According to one embodiment of the invention, it is provided that a zero-point signal is read out immediately at the beginning of the second time period and the flow rate is calculated based on the zero-point signal and the useful signal, in particular based on the difference between the zero-point signal and the useful signal. By difference between zero and
  • the useful signal can also be deducted from any drift voltage remaining despite the short-circuiting of the electrodes, which is not due to the flow of the medium.
  • Evaluation unit has a filter circuit for suppressing high-frequency noise.
  • a filter circuit for suppressing high-frequency noise.
  • Such a filter circuit can, for. B. be designed as a simple low-pass filter, since in most applications thereof
  • Evaluation unit is designed to calculate the flow rate by means of a calibration table.
  • the flow rate calculation formulas known in the art may be used. These formulas take z. B. on that a linear
  • Electrode voltage tapped and stored in a table The
  • Calibration table can be stored in the evaluation unit and the
  • Flow rate can be calculated from the table.
  • the evaluation unit first stores only the signals of the electrodes and a subsequent calibration takes place, d. H. the flow rates for recorded voltage values of the electrodes are only calculated later.
  • the evaluation unit has a microcontroller.
  • the evaluation unit has a microcontroller.
  • MicroController controls a mounted on the measuring device display so that the current flow rate or the total volume of the flowed through medium can be read.
  • the measuring device also has an interface with which the detected values can be transmitted to a computer or via the calibration data from the
  • Measuring device can be stored.
  • the electrodes of the measuring device advantageously have surfaces with high quality, so that electrical deposits are minimized and a detachment of the deposits is simplified.
  • Fig. la is a schematic representation of an inventive
  • Fig. Lb is a schematic representation of an inventive
  • Measuring device in which the signal extraction takes place according to the capacitive principle
  • Fig. 2 is a greatly simplified diagram of the voltage waveform to the
  • Electrodes of a measuring device according to the invention are Electrodes of a measuring device according to the invention.
  • Fig. 3 is a perspective view of an inventive
  • FIG. 4a is a side view of the measuring device of FIG. 3; FIG.
  • Figures 4b, 4c are cross-sectional views of those shown in Figures 3 and 4a
  • Fig. La a simplified representation of a measuring device according to the present invention with galvanic signal extraction is shown.
  • Measuring device 10a in this case has two electrodes 12a, 12b which are in contact with the medium flowing through a pipe 11. Not shown is a magnet which generates a magnetic field (directed into the plane of the drawing). When the medium is flowing, this results in the charge separation and the attachment of positive particles 13a and negative particles 13b on the surfaces of the electrodes 12a, 12b.
  • the electrodes 12a, 12b are connected via leads 14a, 14b to a switch 16 and a differential amplifier 20.
  • the switch 16 is connected in parallel with the inputs of the differential amplifier 20.
  • the switch 16 is switched by a drive unit 18, wherein the
  • Drive unit 18 has a timer (not shown) and also a
  • Evaluation unit 19 controls.
  • the evaluation unit 19 has an analog / digital converter (not shown) and a memory unit.
  • FIG. 1b shows an exemplary embodiment of a measuring device 10b with capacitive signal extraction.
  • the electrodes 12a, 12b are thus arranged outside the tube 11.
  • the interconnection of the remaining elements corresponds to the interconnection of the elements in the measuring device 10a with galvanic signal extraction.
  • Fig. 2 is the diagram (here only very simplified sketched) of a
  • Voltage profile at the electrodes of a measuring device shown.
  • the switch is closed so that the electrodes and the inputs of the differential amplifier are short-circuited.
  • the switch is open for a second period of time 22.
  • a first voltage is applied to the electrodes. This first voltage can be measured as a zero point signal and used to calculate a corrected signal.
  • a transient takes place whose course depends, inter alia, on the capacitance of the measuring circuit. Typically, this leads to an increase in the voltage, with the voltage increase gradually leveling off.
  • a measurement of the useful signal takes place during a third, very short time period 23, thus represented in the diagram as the time.
  • the measurement could be for a period of 1 ps.
  • the switch is closed again for a first period of time and a new cycle begins.
  • Fig. 3 shows a perspective view of a device according to the invention
  • the measuring device 10 has openings 30a, 30b for the inlet or outlet of the medium.
  • the measuring device 10 also has a metallic, cylindrical casing 31.
  • the casing 31 has as few recesses and openings as possible in order to suppress interference signals as much as possible.
  • Placed on the casing 31 is a housing 32 for the evaluation unit and the drive unit.
  • the evaluation unit and the drive unit can, for. B. be realized on the microcontroller.
  • the housing 32 has an opening for a USB socket 34, so that a microcontroller of the measuring device 10 can be connected to a computer.
  • Measuring device also has a display 33, on which the current
  • the measuring device shown in Fig. 3 has no connection for an external power supply, but is powered by an integrated battery. Thus, interference can be prevented by fluctuations of an external power supply.
  • FIG. 4 a shows a side view of the measuring device shown in FIG. 3.
  • FIG. 4b shows a cross section through the measuring device from FIG. 4a and FIG. 3.
  • the cross section shows magnets 40a, 40b which are arranged on opposite sides of a bushing 45.
  • the magnets 40a, 40b are thereby brought into position by screws 42 fastened to the housing holders 41a, 41b.
  • the screws 42 are accessible and the brackets can be loosened and removed.
  • the magnets 41a and 41b become accessible and can be exchanged.
  • the openings 30a, 30b have larger diameters than the passage 45.
  • an increased flow rate is achieved in the passage 45.
  • the implementation has the same or a larger diameter than the openings.
  • Fig. 4C shows a cross-sectional view through the plane in which the electrodes 12a, 12b are arranged.
  • the electrodes are attached to base bodies 15a, 15b.
  • the base body 15a, 15b are, when the sheath 31 is removed, accessible from the outside, so that the electrodes 12a, 12b can optionally be replaced with the base bodies 15a, 15b.
  • the microcontroller on which the drive unit and the evaluation unit are located.
  • the microcontroller should be arranged in the housing 32.
  • the switch 16 and an amplifier 20 are in the housing 32.
  • the switch 16 is arranged directly on the electrodes 12a, 12b in order to achieve the lowest possible short circuit resistance.
  • the leads 14a, 14b from the electrodes 12a, 12b to the switch 16 and amplifier 20 are thus different according to this embodiment long. In other embodiments, it may be provided that the
  • Supply lines are formed symmetrically.
  • the supply lines 14a, 14b are shown only shortened in Fig. 4C.
  • reinforced wires or strands are used for the leads, so that a low short-circuit resistance is achieved.

Landscapes

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

Abstract

L'invention concerne un dispositif de mesure pour la mesure de la vitesse d'écoulement d'un milieu électriquement conducteur dans un volume traversé par un champ magnétique, présentant - un moyen de génération du champ magnétique, - au moins deux électrodes et - une unité d'évaluation qui exploite un signal des électrodes et calcule la vitesse d'écoulement. Les au moins deux électrodes sont reliées à un commutateur qui est conçu pour court-circuiter les électrodes.
EP13719549.1A 2012-04-30 2013-04-30 Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu Withdrawn EP2844960A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP13719549.1A EP2844960A1 (fr) 2012-04-30 2013-04-30 Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
PCT/EP2012/057939 WO2013164011A1 (fr) 2012-04-30 2012-04-30 Dispositif et procédé de mesure de la vitesse d'écoulement d'un fluide
PCT/EP2013/058962 WO2013164329A1 (fr) 2012-04-30 2013-04-30 Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu
EP13719549.1A EP2844960A1 (fr) 2012-04-30 2013-04-30 Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu

Publications (1)

Publication Number Publication Date
EP2844960A1 true EP2844960A1 (fr) 2015-03-11

Family

ID=52441460

Family Applications (1)

Application Number Title Priority Date Filing Date
EP13719549.1A Withdrawn EP2844960A1 (fr) 2012-04-30 2013-04-30 Dispositif de mesure destiné à la mesure de la vitesse d'écoulement d'un milieu

Country Status (1)

Country Link
EP (1) EP2844960A1 (fr)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2013164329A1 *

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