WO2010121631A1 - Electromagnetic flowmeter and method of operation thereof - Google Patents
Electromagnetic flowmeter and method of operation thereof Download PDFInfo
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- WO2010121631A1 WO2010121631A1 PCT/EP2009/002936 EP2009002936W WO2010121631A1 WO 2010121631 A1 WO2010121631 A1 WO 2010121631A1 EP 2009002936 W EP2009002936 W EP 2009002936W WO 2010121631 A1 WO2010121631 A1 WO 2010121631A1
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- flowmeter
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- 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
- Electromagnetic flowmeter and method of operation thereof are Electromagnetic flowmeter and method of operation thereof
- the present invention relates to electromagnetic flowmeters for measurement of fluid flow rate, and in particular, to condition monitoring in such flowmeters.
- Electromagnetic flowmeters utilize the principle of electrodynamic induction for flow rate measurement of a fluid medium.
- a magnetic field is generated across a measuring section of the flowmeter pipe through which the medium flows, which, by operation of
- Such an electromagnetic flowmeter is, in principle, a black box. If there is no differential electrode signal, it is assumed that there is no flow. That is, there is no way to monitor operational failures which may lead to no differential electrode signal, for example, when there is a short circuit of the electrodes, or when no current is flowing through the coils in the magnetic circuit.
- the object of the present invention is to provide an improved electromagnetic flowmeter and method of operation thereof.
- the above object is achieved by the features of the present invention as set forth in claims 1 and 8.
- the differential electrode signal is proportional to the flow velocity only if the magnetic field is stable. Therefore, for a given pulse of the magnetic field accurate flow measurements would be possible only for a time period when the magnetic field is stable.
- the underlying idea of the present invention is that, by measuring the differential electrode signal in the period when the magnetic field is stabilizing, it is possible to monitor the health of the flowmeter. During this period, the differential electrode signal is dominated by the rate of change of the magnetic field. Hence a measurement of the differential electrode signal during this period would make it possible to verify if the coil current is resulting in the magnetic field, which again is resulting in the differential electrode signal.
- the flowmeter comprises a flow measurement module adapted for determining flow rate of said fluid based on measurement of said differential electrode signal during a second period within the duration of said pulse, said second period corresponding to a time interval within said pulse after said magnetic field has stabilized.
- the differential electrode signal is proportional to the flow rate during the second period, and hence it is possible to accurately measure the fluid flow rate during this period.
- the condition monitoring module is adapted to determine an operational condition as abnormal when said differential electrode signal measured during said first period is lesser than a reference value. It is shown herein that under normal operating conditions, i.e., when there is current in the magnetic coils and the electrodes are not short circuited, the differential electrode signal would shows a high peak value at the beginning of the pulse. The absence or reduction of this value (with respect to a reference value) can therefore be used to indicate an abnormal operational condition.
- the condition monitoring module is further adapted for measurement of individual potentials of each of said electrodes with respect to ground within the duration of said first period, and determining an operational condition of said flowmeter based upon a comparison of the measured individual potentials of said electrodes with respect to ground. This can be used to check balance of electrode to ground impedance through the fluid medium
- Electrode surface contamination electrode surface contamination
- each electrode of said pair of electrodes is provided with an electrode cable made with a loop of equal area and identical turn direction and positioned such that said magnetic field passes through said loops of said electrode cables.
- the flowmeter further comprises means for displaying the determined operational condition of said flowmeter.
- the flowmeter comprises a microprocessor adapted to execute said condition monitoring module and said flow measurement module.
- the microprocessor can be advantageously programmed to process the differential electrode signal during the first and second periods distinctly. The durations of the first and second periods can be preprogrammed into the microprocessor.
- FIG 1 is a schematic diagram of an electromagnetic flowmeter having a condition monitoring module according to one embodiment of the present invention
- FIG 2 is a graphical representation of the variation of the measured differential electrode signal during one pulse of the magnetic field
- FIG 3 is a schematic diagram of an electromagnetic flowmeter arrangement according to a further embodiment of the present invention for monitoring electrode to ground impedance through the fluid medium, and
- FIGS 4A and 4B are graphical representations of the variation of the individual electrode potentials of the measuring electrodes with respect to ground during one pulse of the magnetic field.
- an electromagnetic flowmeter 10 includes a measurement tube 12 extending along an axis 40.
- the measurement tube 12 defines a passage for flow of a fluid media 14 whose flow rate is to be measured.
- the fluid 14 to be measured is electrically conductive, at least to a slight extent.
- Measuring electrodes 16 and 18 are arranged on opposite sides of the measurement tube 12.
- a non-conducting liner 38 may be disposed along the inner surface of the measurement tube 12 to prevent the electrodes 16 and 18 from being short circuited.
- a magnetic circuit comprising coils 44 and 46 that are excitable by a pulsed alternating current signal 49 from a current source 48.
- the pulsed current signal 49 is generated to have a substantially constant value during one pulse of the current signal 49, approaching a square waveform.
- the excitation of the coils 44 and 46 results in a pulsed magnetic field 42 of alternating polarity that is oriented perpendicularly to the direction of flow of the fluid 14.
- charge carriers in the fluid media 14 migrate to the measuring electrodes 16 and 18 of opposite polarity thus building up a potential difference across the electrodes 16 and 18.
- Flow measurement means 24, such as a differential amplifier amplifies this potential difference (i.e. the difference in the output signals 22 and 20 from the measuring electrodes 16 and 18 respectively) and provides a differential electrode signal 26.
- the differential electrode signal 26 is proportional to the flow velocity of the fluid 14 (averaged over the cross- sectional area of the measurement tube 12) when the magnetic field 42 has stabilized (i.e., becomes constant). However, when the magnetic field 42 is in the process of stabilizing, the differential electrode signal 26 is a function of both the fluid velocity and the rate of change of magnetic flux d ⁇ /dt.
- FIG 2 depicts a curve 50 showing a typical variation of the differential electrode signal E 0 (V), represented along the axis 52 with time t(ms) represented along the axis 54.
- the curve 50 is herein discussed within the duration Pi of one pulse of the magnetic field.
- the magnetic flux increases rapidly (i.e. d ⁇ /dt is very high at the start of the pulse) , due to which the differential electrode signal has a very steep spike from a negative value to a positive peak value E D (p ea k) at the beginning of the pulse.
- the rate of change of magnetic flux d ⁇ /dt subsequently decreases till the time the magnetic field stabilizes. Till the time the magnetic field stabilizes (i.e. till d ⁇ /dt becomes zero), the differential electrode signal is a function of both, the rate of change of flux d ⁇ /dt and the flow velocity of the fluid, the rate of change of magnetic flux being the more dominant factor.
- the period before the magnetic flux has stabilized is indicated by ti.
- differential electrode signal gradually decreases with time till the curve 50 becomes asymptotic with the time axis 54.
- differential electrode signal is proportional to the flow velocity of the fluid, till the onset of the next pulse of the magnetic field which is of opposite polarity.
- the present invention proposes to utilize the first period ti for condition monitoring of the flowmeter.
- the second period t 2 may be utilized for flow measurement.
- the differential electrode signal By measuring the differential electrode signal during the first period ti when the magnetic field is stabilizing, it is possible to monitor the health of the flowmeter. For example, if individual potentials of each of said electrodes (16, 18) with respect to ground or the differential electrode signal is measured to be zero in the first period ti, it indicates an operational failure, arising, for example, when no current flows through the magnetic coils, or measuring electrodes are partially or fully short circuited, which may take place if the liner is destroyed or, if there is a deposit of a conductive layer on the liner. This makes it possible for appropriate remedial action or repair work.
- an abnormal operational condition may be indicated whenever individual potentials of each of said electrodes (16, 18) with respect to ground or the differential electrode signal measured in the first period ti is lesser than a predetermined reference value.
- the differential electrode signal would show a high peak value E D( p eak ) at the beginning of the pulse. The absence or any reduction in this peak value can therefore be used to indicate an abnormal operational condition.
- the proposed flowmeter 10 includes a condition monitoring module 30, executed, for example, by a microprocessor 28, for determining an operational condition of the flowmeter 10 by measuring the differential electrode signal 26 for a first period in the duration of a pulse of the magnetic field 42 when the magnetic field 42 is stabilizing, as discussed referring to FIG 2. Based upon the measured differential electrode signal during this first period, the operational status of the flowmeter, or any abnormality thereof, can be notified to the user via display means 36. As an example, the display means 36 may simply include an LED with an ON/OFF function to indicate whether or not the flowmeter is functioning normally. Determination of flow rate of the fluid is carried out by a flow measurement module 32 executed by the microprocessor 28 by measurement of the differential electrode signal 26 during the second period of the pulse.
- the flow measurement module 32 calibrates the differential electrode signal 26 measured during the second period to units of flow velocity or flow rate, and provides an output to output circuitry 34.
- the condition monitoring module and the flow measurement module may be implemented by preprogramming durations of the first and second periods in the pulse into the microprocessor 28.
- the first period would correspond to a time interval within a pulse before the magnetic field has stabilized.
- the second period would correspond to a time interval within the pulse after the magnetic field has stabilized.
- condition monitoring module may be extended to check balance of electrode to ground impedance through the fluid media. This can be achieved by measuring each individual electrode potential with respect to ground during the first period ti of the pulse, when the magnetic field is stabilizing, and comparing these measured individual electrode potentials with respect to ground.
- FIG 3 shows an exemplary arrangement for carrying out the same.
- the measuring electrodes 16 and 18 arranged on opposite sides of the measurement tube 12 are provided with electrode cables that are made with respective loops 156 and 158.
- These loops 156 and 158 have equal area and identical turn directions, and are positioned such that the magnetic field 42 passes through the loops 156 and 158.
- the arrangement described herein advantageously provides an enhanced signal for measurement of electrode potential with respect to ground that may be used for determining the operational condition by comparison to a reference value.
- FIG 4A shows the variation of the potential of the electrode 16 with respect to the ground (represented by curve 70) in the duration Pi of a pulse of the magnetic field, wherein the axis 72 represents the potential Ei 6 (V) of the electrode 16 with respect to ground and the axis 74 represents time t(ms) .
- the electrode potential of the electrode 16 with respect to ground has a very steep spike from a negative value to a positive peak value E 16 (p ea k) at the beginning of the pulse.
- E 16 p ea k
- the loops 156 and 158 are of equal area and have identical turn directions, under normal operating conditions, a similar variation can be observed with respect to the potential of the electrode 18 with respect to ground during the pulse Pi, as depicted by the curve 80 in FIG 4B, wherein the axis 82 represents the potential Ei 8 (V) of the electrode 18 with respect to ground and the axis 84 represents time t(ms).
- the individual electrode potentials Ei 6 and Ei 8 should be substantially equal, although not exactly equal in value.
- the potentials Ei 6 and Ei 8 cannot be fully identical as the effect of the varying field in the fluid will add to one of the signals 22 and 22 and be subtracted from the other.
- the condition monitoring module 30 can be adapted to determine an abnormal operational condition (such as, a possible short circuit in one of the electrodes or an electrode surface contamination) in case of any inequality in the measured individual electrode potentials (i.e, the signals 20 and 22 measured individually) during the first period t x , beyond an accepted tolerance limit.
- an abnormal operational condition such as, a possible short circuit in one of the electrodes or an electrode surface contamination
- the present invention provides an electromagnetic flowmeter and a method of operation thereof.
- the proposed flowmeter comprises a measurement tube defining a passage for carrying a fluid whose flow is to be measured.
- a magnetic circuit is provided having a pair of coils excitable by a pulsed alternating current signal to generate a pulsed magnetic field oriented perpendicularly to a direction of flow of said fluid.
- a pair of electrodes is positioned on opposite sides of said measurement tube.
- the proposed flowmeter further comprises a condition monitoring module adapted for determining an operational condition of the flowmeter based upon measurement of individual potentials of each of said electrodes with respect to ground or upon measurement of a differential electrode signal obtained from a difference between output signals of said electrodes. This measurement is carried out during a first period within the duration of one pulse of said magnetic field, said first period corresponding to a time interval within said pulse before said magnetic field has stabilized.
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Abstract
The present invention provides an electromagnetic flowmeter and a method of operation thereof. The proposed flowmeter (10) comprises a measurement tube (12) defining a passage for carrying a fluid (14) whose flow is to be measured. A magnetic circuit is provided having a pair of coils (44, 46) excitable by a pulsed alternating current signal (49), to generate a pulsed magnetic field (42) oriented perpendicularly to a direction of flow of said fluid (14). A pair of electrodes (16, 18) is arranged on opposite sides of said measurement tube (12). The proposed flowmeter (10) further comprises a condition monitoring module (30) adapted for determining an operational condition of the flowmeter (10) based upon measurement of individual potentials of each of said electrodes (16, 18) with respect to ground or upon measurement of a differential electrode signal (26) obtained from a difference between output signals (22, 20) of said electrodes (16, 18). This measurement is carried out during a first period (ti) within the duration (P1) of one pulse of said magnetic field (42), said first period (t1) corresponding to a time interval within said duration (P1) of the pulse before said magnetic field (42) has stabilized.
Description
Description
Electromagnetic flowmeter and method of operation thereof
The present invention relates to electromagnetic flowmeters for measurement of fluid flow rate, and in particular, to condition monitoring in such flowmeters.
Electromagnetic flowmeters utilize the principle of electrodynamic induction for flow rate measurement of a fluid medium. In an electromagnetic flowmeter, a magnetic field is generated across a measuring section of the flowmeter pipe through which the medium flows, which, by operation of
Faraday's law, generates a voltage perpendicular to both the flow of the medium and the magnetic field. This induced voltage is measured by a pair of electrodes on opposite sides of the measuring section as a difference between the output signals of these electrodes. When the magnetic field is stable, this differential electrode signal from the measuring electrodes is proportional to the flow velocity of the medium to be measured averaged over the cross section of the pipe.
However, such an electromagnetic flowmeter is, in principle, a black box. If there is no differential electrode signal, it is assumed that there is no flow. That is, there is no way to monitor operational failures which may lead to no differential electrode signal, for example, when there is a short circuit of the electrodes, or when no current is flowing through the coils in the magnetic circuit.
Currently, flowmeter functions are verified by checking electrode impedance and magnetic circuit inductance (or time constant) .
The object of the present invention is to provide an improved electromagnetic flowmeter and method of operation thereof. The above object is achieved by the features of the present invention as set forth in claims 1 and 8.
It is known that the differential electrode signal is proportional to the flow velocity only if the magnetic field is stable. Therefore, for a given pulse of the magnetic field accurate flow measurements would be possible only for a time period when the magnetic field is stable. The underlying idea of the present invention is that, by measuring the differential electrode signal in the period when the magnetic field is stabilizing, it is possible to monitor the health of the flowmeter. During this period, the differential electrode signal is dominated by the rate of change of the magnetic field. Hence a measurement of the differential electrode signal during this period would make it possible to verify if the coil current is resulting in the magnetic field, which again is resulting in the differential electrode signal.
Accordingly, in a further embodiment of the present invention, the flowmeter comprises a flow measurement module adapted for determining flow rate of said fluid based on measurement of said differential electrode signal during a second period within the duration of said pulse, said second period corresponding to a time interval within said pulse after said magnetic field has stabilized. The differential electrode signal is proportional to the flow rate during the second period, and hence it is possible to accurately measure the fluid flow rate during this period.
In one embodiment, the condition monitoring module is adapted to determine an operational condition as abnormal when said differential electrode signal measured during said first period is lesser than a reference value. It is shown herein that under normal operating conditions, i.e., when there is current in the magnetic coils and the electrodes are not short circuited, the differential electrode signal would shows a high peak value at the beginning of the pulse. The absence or reduction of this value (with respect to a reference value) can therefore be used to indicate an abnormal operational condition.
In a further embodiment, the condition monitoring module is further adapted for measurement of individual potentials of each of said electrodes with respect to ground within the duration of said first period, and determining an operational condition of said flowmeter based upon a comparison of the measured individual potentials of said electrodes with respect to ground. This can be used to check balance of electrode to ground impedance through the fluid medium
(electrode surface contamination) .
In a preferred further embodiment, to provide an enhanced signal for checking balance of electrode to ground impedance, each electrode of said pair of electrodes is provided with an electrode cable made with a loop of equal area and identical turn direction and positioned such that said magnetic field passes through said loops of said electrode cables.
In a preferred embodiment, to provide information on the operating status of said flowmeter, the flowmeter further comprises means for displaying the determined operational condition of said flowmeter.
In one embodiment, the flowmeter comprises a microprocessor adapted to execute said condition monitoring module and said flow measurement module. The microprocessor can be advantageously programmed to process the differential electrode signal during the first and second periods distinctly. The durations of the first and second periods can be preprogrammed into the microprocessor.
The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:
FIG 1 is a schematic diagram of an electromagnetic flowmeter having a condition monitoring module according to one embodiment of the present invention,
FIG 2 is a graphical representation of the variation of the measured differential electrode signal during one pulse of the magnetic field,
FIG 3 is a schematic diagram of an electromagnetic flowmeter arrangement according to a further embodiment of the present invention for monitoring electrode to ground impedance through the fluid medium, and
FIGS 4A and 4B are graphical representations of the variation of the individual electrode potentials of the measuring electrodes with respect to ground during one pulse of the magnetic field.
Embodiments of the present invention discussed below provide an electromagnetic flowmeter having means for self condition monitoring to provide increased reliability for flow measurement. Such a flowmeter is discussed referring to FIG 1. Herein, an electromagnetic flowmeter 10 includes a measurement tube 12 extending along an axis 40. The measurement tube 12 defines a passage for flow of a fluid media 14 whose flow rate is to be measured. The fluid 14 to be measured is electrically conductive, at least to a slight extent. Measuring electrodes 16 and 18 are arranged on opposite sides of the measurement tube 12. A non-conducting liner 38 may be disposed along the inner surface of the measurement tube 12 to prevent the electrodes 16 and 18 from being short circuited. A magnetic circuit is provided comprising coils 44 and 46 that are excitable by a pulsed alternating current signal 49 from a current source 48. The pulsed current signal 49 is generated to have a substantially constant value during one pulse of the current signal 49, approaching a square waveform. The excitation of the coils 44 and 46 results in a pulsed magnetic field 42 of alternating polarity that is oriented perpendicularly to the direction of flow of the fluid 14. On account of this magnetic field 42, charge carriers in the fluid media 14 migrate to the measuring electrodes 16 and 18 of opposite polarity thus
building up a potential difference across the electrodes 16 and 18. Flow measurement means 24, such as a differential amplifier, amplifies this potential difference (i.e. the difference in the output signals 22 and 20 from the measuring electrodes 16 and 18 respectively) and provides a differential electrode signal 26.
The differential electrode signal 26 is proportional to the flow velocity of the fluid 14 (averaged over the cross- sectional area of the measurement tube 12) when the magnetic field 42 has stabilized (i.e., becomes constant). However, when the magnetic field 42 is in the process of stabilizing, the differential electrode signal 26 is a function of both the fluid velocity and the rate of change of magnetic flux dΦ/dt.
The above is illustrated referring to FIG 2, which depicts a curve 50 showing a typical variation of the differential electrode signal E0(V), represented along the axis 52 with time t(ms) represented along the axis 54. The curve 50 is herein discussed within the duration Pi of one pulse of the magnetic field.
As can be seen, at the beginning of the pulse, the magnetic flux increases rapidly (i.e. dΦ/dt is very high at the start of the pulse) , due to which the differential electrode signal has a very steep spike from a negative value to a positive peak value ED(peak) at the beginning of the pulse. The rate of change of magnetic flux dΦ/dt subsequently decreases till the time the magnetic field stabilizes. Till the time the magnetic field stabilizes (i.e. till dΦ/dt becomes zero), the differential electrode signal is a function of both, the rate of change of flux dΦ/dt and the flow velocity of the fluid, the rate of change of magnetic flux being the more dominant factor. The period before the magnetic flux has stabilized is indicated by ti. During this period, differential electrode signal gradually decreases with time till the curve 50 becomes asymptotic with the time axis 54. Thereafter, in the
period t2, differential electrode signal is proportional to the flow velocity of the fluid, till the onset of the next pulse of the magnetic field which is of opposite polarity. The present invention proposes to utilize the first period ti for condition monitoring of the flowmeter. The second period t2 may be utilized for flow measurement.
By measuring the differential electrode signal during the first period ti when the magnetic field is stabilizing, it is possible to monitor the health of the flowmeter. For example, if individual potentials of each of said electrodes (16, 18) with respect to ground or the differential electrode signal is measured to be zero in the first period ti, it indicates an operational failure, arising, for example, when no current flows through the magnetic coils, or measuring electrodes are partially or fully short circuited, which may take place if the liner is destroyed or, if there is a deposit of a conductive layer on the liner. This makes it possible for appropriate remedial action or repair work. In general, an abnormal operational condition may be indicated whenever individual potentials of each of said electrodes (16, 18) with respect to ground or the differential electrode signal measured in the first period ti is lesser than a predetermined reference value. For example, under normal operating conditions, i.e., when there is current in the magnetic coils and the electrodes are not short circuited, the differential electrode signal would show a high peak value ED(peak) at the beginning of the pulse. The absence or any reduction in this peak value can therefore be used to indicate an abnormal operational condition.
Referring back to FIG 1, the proposed flowmeter 10 includes a condition monitoring module 30, executed, for example, by a microprocessor 28, for determining an operational condition of the flowmeter 10 by measuring the differential electrode signal 26 for a first period in the duration of a pulse of the magnetic field 42 when the magnetic field 42 is stabilizing, as discussed referring to FIG 2. Based upon the
measured differential electrode signal during this first period, the operational status of the flowmeter, or any abnormality thereof, can be notified to the user via display means 36. As an example, the display means 36 may simply include an LED with an ON/OFF function to indicate whether or not the flowmeter is functioning normally. Determination of flow rate of the fluid is carried out by a flow measurement module 32 executed by the microprocessor 28 by measurement of the differential electrode signal 26 during the second period of the pulse. The flow measurement module 32 calibrates the differential electrode signal 26 measured during the second period to units of flow velocity or flow rate, and provides an output to output circuitry 34. The condition monitoring module and the flow measurement module may be implemented by preprogramming durations of the first and second periods in the pulse into the microprocessor 28. The first period would correspond to a time interval within a pulse before the magnetic field has stabilized. The second period would correspond to a time interval within the pulse after the magnetic field has stabilized.
The functionality of the condition monitoring module may be extended to check balance of electrode to ground impedance through the fluid media. This can be achieved by measuring each individual electrode potential with respect to ground during the first period ti of the pulse, when the magnetic field is stabilizing, and comparing these measured individual electrode potentials with respect to ground.
FIG 3 shows an exemplary arrangement for carrying out the same. Herein, the measuring electrodes 16 and 18 arranged on opposite sides of the measurement tube 12 are provided with electrode cables that are made with respective loops 156 and 158. These loops 156 and 158 have equal area and identical turn directions, and are positioned such that the magnetic field 42 passes through the loops 156 and 158. The arrangement described herein advantageously provides an enhanced signal for measurement of electrode potential with
respect to ground that may be used for determining the operational condition by comparison to a reference value.
FIG 4A shows the variation of the potential of the electrode 16 with respect to the ground (represented by curve 70) in the duration Pi of a pulse of the magnetic field, wherein the axis 72 represents the potential Ei6(V) of the electrode 16 with respect to ground and the axis 74 represents time t(ms) . As in case of the differential electrode signal, the electrode potential of the electrode 16 with respect to ground has a very steep spike from a negative value to a positive peak value E16(peak) at the beginning of the pulse. During the period tx, the rate of change of magnetic flux dΦ/dt subsequently decreases till the time the magnetic field stabilizes. In the period t2 after the magnetic field has stabilized, the potential of the electrode 16 with respect to ground reaches a steady value.
Given that the loops 156 and 158 are of equal area and have identical turn directions, under normal operating conditions, a similar variation can be observed with respect to the potential of the electrode 18 with respect to ground during the pulse Pi, as depicted by the curve 80 in FIG 4B, wherein the axis 82 represents the potential Ei8(V) of the electrode 18 with respect to ground and the axis 84 represents time t(ms). Under normal operating conditions, the individual electrode potentials Ei6 and Ei8 should be substantially equal, although not exactly equal in value. As can be understood, the potentials Ei6 and Ei8 cannot be fully identical as the effect of the varying field in the fluid will add to one of the signals 22 and 22 and be subtracted from the other. However, advantageously, in this embodiment, this difference is negligible as the potential induced in the loops 156 and 158 are much larger compared to this differential potential caused by variation of magnetic field in the fluid. Hence, under a normal operating condition, the peak value Ei8(peak) should also be substantially equal to the peak value Ei6(peak), with a small margin of tolerance.
Accordingly, the condition monitoring module 30 can be adapted to determine an abnormal operational condition (such as, a possible short circuit in one of the electrodes or an electrode surface contamination) in case of any inequality in the measured individual electrode potentials (i.e, the signals 20 and 22 measured individually) during the first period tx, beyond an accepted tolerance limit.
Summarizing, the present invention provides an electromagnetic flowmeter and a method of operation thereof. The proposed flowmeter comprises a measurement tube defining a passage for carrying a fluid whose flow is to be measured. A magnetic circuit is provided having a pair of coils excitable by a pulsed alternating current signal to generate a pulsed magnetic field oriented perpendicularly to a direction of flow of said fluid. A pair of electrodes is positioned on opposite sides of said measurement tube. The proposed flowmeter further comprises a condition monitoring module adapted for determining an operational condition of the flowmeter based upon measurement of individual potentials of each of said electrodes with respect to ground or upon measurement of a differential electrode signal obtained from a difference between output signals of said electrodes. This measurement is carried out during a first period within the duration of one pulse of said magnetic field, said first period corresponding to a time interval within said pulse before said magnetic field has stabilized.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined by the below-mentioned patent claims.
Claims
1. An electromagnetic flowmeter (10), comprising: a measurement tube (12) defining a passage for carrying a fluid (14) whose flow is to be measured,
- a magnetic circuit comprising a pair of coils (44, 46) excitable by a pulsed alternating current signal (49), to generate a pulsed magnetic field (42) oriented perpendicularly to a direction of flow of said fluid (14) ,
- a pair of electrodes (16, 18) positioned on opposite sides of said measurement tube (12), and a condition monitoring module (30) adapted for determining an operational condition of said flowmeter (10) based upon measurement of individual potentials of each of said electrodes (16, 18) with respect to ground or upon measurement of a differential electrode signal (26) obtained from a difference between output signals (22, 20) of said electrodes (16, 18), said measurement being carried out during a first period (ti) within the duration
(Pi) of one pulse of said magnetic field (42), said first period (ti) corresponding to a time interval within said pulse before said magnetic field (42) has stabilized.
2. The flowmeter (10) according to claim 1, further comprising a flow measurement module (32) adapted for determining flow rate of said fluid (14) based on measurement of said differential electrode signal (26) during a second period (t2) within the duration (Pi) of said pulse, said second period (t2) corresponding to a time interval within said duration (Pi) of the pulse after said magnetic field (42) has stabilized.
3. The flowmeter (10) according to any of the preceding claims, wherein said condition monitoring module (30) is adapted to determine an operational condition as abnormal when said individual potentials of each of said electrodes (16, 18) with respect to ground or said differential electrode signal measured (26) during said first period (ti) is lesser than a reference value.
4. The flowmeter (10) according to any of the preceding claims, wherein said condition monitoring module (30) is further adapted for measurement of individual potentials of each of said electrodes (16, 18) with respect to ground within the duration of said first period (ti) , and determining an operational condition of said flowmeter (10) based upon a comparison to each other of the measured individual potentials of said electrodes (16, 18) with respect to ground during said first period (ti) .
5. The flowmeter (10) according to any of the preceding claims, wherein each electrode (16, 18) of said pair of electrodes (16, 18) is provided with an electrode cable made with a loop (156, 158) of equal area and identical turn direction and positioned such that said magnetic field (42) passes through said loops (156, 158) of said electrode cables.
6. The flowmeter (10) according to any of the preceding claims, further comprising means (36) for displaying the determined operational condition of said flowmeter
(10) .
7. The flowmeter (10) according to any of claims 2 to 6, comprising a microprocessor (28) adapted to execute said condition monitoring module (30) and said flow measurement module (32).
8. A method for operating an electromagnetic flowmeter (10), comprising:
- generating a pulsed magnetic field (42) by exciting a pair of coils (44, 46) by a pulsed alternating current signal (49), said magnetic field (42) being oriented perpendicularly to a direction of flow of a fluid (14) through a measuring tube (12),
- obtaining a differential electrode signal (26) based on a difference between output signals (22, 20) of a pair of electrodes (16, 18) arranged on opposite sides of said measuring tube (12), and determining an operational condition of said flowmeter (10) based upon measurement of individual potentials of each of said electrodes (16, 18) with respect to ground or upon measurement of said differential electrode signal (26) during a first period (ti) within the duration of one pulse (Pi) of said magnetic field (42), said first period (ti) corresponding to a time interval within said duration (Pi) of the pulse before said magnetic field (42) has stabilized.
9. The method according to claim 8, further comprising determining flow rate of said fluid (14) based on measurement of said differential electrode signal (26) during a second period (t2) within the duration (Pi) of said pulse, said second period (t2) corresponding to a time interval within said duration (Pi) of the pulse after said magnetic field (42) has stabilized.
10. The method according to any of claims 8 and 9, comprising determining an operational condition as abnormal when said individual potentials of each of said electrodes (16, 18) with respect to ground or said differential electrode signal (26) measured during said first period (ti) is lesser than a reference value.
11. The method according to any of claims 8 to 10, further comprising:
- measuring individual potentials of each of said electrodes (16, 18) with respect to ground within the duration of said first period (ti) , and determining an operational condition of said flowmeter (10) based upon a comparison to each other of the measured individual potentials of said electrodes (16, 18) with respect to ground during said first period (ti) .
12. The method according to claim 11, further comprising:
- providing each electrode (16, 18) of said pair of electrodes (16, 18) with an electrode cable made with a loop (156, 158) of egual area and identical turn direction, and
- positioning said electrodes (16, 18) such that said magnetic field (42) passes through said loops (156, 158) of said electrode cables.
13. The method according to any of claims 8 to 12, further comprising displaying said operational condition of said flowmeter (10).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/EP2009/002936 WO2010121631A1 (en) | 2009-04-22 | 2009-04-22 | Electromagnetic flowmeter and method of operation thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/EP2009/002936 WO2010121631A1 (en) | 2009-04-22 | 2009-04-22 | Electromagnetic flowmeter and method of operation thereof |
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| Publication Number | Publication Date |
|---|---|
| WO2010121631A1 true WO2010121631A1 (en) | 2010-10-28 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/EP2009/002936 WO2010121631A1 (en) | 2009-04-22 | 2009-04-22 | Electromagnetic flowmeter and method of operation thereof |
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| Country | Link |
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| WO (1) | WO2010121631A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2618584C1 (en) * | 2016-02-26 | 2017-05-04 | Акционерное общество научно-исследовательский институт теплоэнергетического приборостроения "НИИТеплоприбор" | Electromagnetic flow converter |
| EP2972123B1 (en) * | 2013-03-14 | 2020-12-09 | Micro Motion, Inc. | Magnetic flowmeter with automatic adjustment based on sensed complex impedance |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5370000A (en) | 1991-07-04 | 1994-12-06 | Fischer & Porter Company | Magnetic flowmeter with fault detection |
| US20020145417A1 (en) * | 2001-04-10 | 2002-10-10 | Helmut Brockhaus | Magnetoinductive flowmeter and magnetoinductuve flow-measuring process |
| WO2007033697A1 (en) * | 2005-09-21 | 2007-03-29 | Siemens Aktiengesellschaft | Method for operating an electromagnetic flowmeter and electomagnetic flowmeter |
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2009
- 2009-04-22 WO PCT/EP2009/002936 patent/WO2010121631A1/en active Application Filing
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5370000A (en) | 1991-07-04 | 1994-12-06 | Fischer & Porter Company | Magnetic flowmeter with fault detection |
| US20020145417A1 (en) * | 2001-04-10 | 2002-10-10 | Helmut Brockhaus | Magnetoinductive flowmeter and magnetoinductuve flow-measuring process |
| WO2007033697A1 (en) * | 2005-09-21 | 2007-03-29 | Siemens Aktiengesellschaft | Method for operating an electromagnetic flowmeter and electomagnetic flowmeter |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2972123B1 (en) * | 2013-03-14 | 2020-12-09 | Micro Motion, Inc. | Magnetic flowmeter with automatic adjustment based on sensed complex impedance |
| RU2618584C1 (en) * | 2016-02-26 | 2017-05-04 | Акционерное общество научно-исследовательский институт теплоэнергетического приборостроения "НИИТеплоприбор" | Electromagnetic flow converter |
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