JP2001241981A - Electromagnetic flow meter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the performance of flow rate measurement by reliably measuring the flow velocity of a fluid to be measured having a low conductivity or a minute flow. The measuring section has an inner wall section that is flattened and the inside of which is arranged on a measuring tube 11 through which a fluid to be measured flows and a flattened surface of the measuring tube 11 with a short interval.
1, a coil 12 for applying a magnetic field in a direction substantially perpendicular to the tube axis direction, and a flat surface of the measuring tube 11 with a long interval therebetween, which is opposed to the coil 12 for generating a magnetic field. It includes a pair of electromagnetics 13 for extracting electric power, and a yoke 14 that is arranged so as to surround the measuring tube 11, the coil 12, and the electrode 13, and that forms a 12-core coil and a return path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromotive force generated by flowing a fluid to be measured inside a measuring tube, applying a magnetic field to the fluid to be measured by a coil, and moving the fluid to be measured in the magnetic field. The present invention relates to an electromagnetic flowmeter that takes out a pair of electrodes and detects the flow velocity of a fluid to be measured from the electromotive force, and particularly relates to an electromagnetic flowmeter that can greatly improve the performance of flow velocity measurement.

[0002]

2. Description of the Related Art Conventionally, as one of the electromagnetic flowmeters for detecting the flow velocity of a fluid to be measured, a fluid to be measured is caused to flow inside a measuring tube, and a magnetic field is applied to the fluid to be measured by a coil. Electromagnetic flowmeters are used in which an electromotive force generated by movement of a fluid to be measured is extracted by a pair of electrodes, and the flow rate of the fluid to be measured is detected from the electromotive force.

FIG. 6 is a sectional view showing an example of the configuration of a measuring section of a conventional electromagnetic flowmeter of this type.

In FIG. 6, an electromagnetic flowmeter has a cylindrical measuring pipe 61 through which a fluid to be measured flows, and is arranged on both sides of the measuring pipe 61 so as to be curved along the measuring pipe 61 so as to measure the fluid to be measured. A pair of coils 62 for providing a magnetic field in a direction substantially perpendicular to the tube axis direction of the tube 61, and an electromotive force generated by the fluid to be measured moving in the magnetic field, disposed opposite to both surfaces in a direction substantially perpendicular to the coil 62. A pair of electromagnetic 6 to take out
3 and a yoke 64 that is arranged so as to surround the measurement tube 61, the coil 62, and the electrode 63, and forms a core of the coil 62 and a return magnetic path.

FIG. 7 is a conceptual diagram showing Faraday's electromagnetic induction law, which is the principle of measuring the flow velocity of such a conventional electromagnetic flowmeter.

In FIG. 7, when a conductor passes through a magnetic field, the magnetic flux density 71 of the magnetic field, the moving speed 72 of the conductor that crosses the magnetic flux almost vertically, and the width 73 of the conductor make the magnetic flux and the moving direction substantially perpendicular. The electromotive force 74 is generated in a different direction.

The electromotive force is e (V), the magnetic flux density is B (T),
Assuming that the width of the conductor is D (cm) and the moving speed is v (cm / s), the following holds: e = B · D · v × 10 ⁻⁴ .

That is, in the electromagnetic flow meter, the fluid to be measured flows inside the measuring tube 61 and the magnetic field generated by the coil 62 is
The yoke 64 is applied in a direction substantially perpendicular to the flow of the fluid to be measured, and the electromotive force generated in a direction substantially perpendicular to the flow of the fluid to be measured and the magnetic field is taken out by the pair of electrodes 63.

[0009]

However, such a conventional electromagnetic flowmeter has the following problems.

That is, since a fluid to be measured having a low conductivity has a large flow noise, it is difficult to detect an electromotive force. In particular, when the flow velocity of the fluid to be measured increases, the flow noise also increases, and the flow velocity cannot be measured.

On the other hand, the fluid to be measured having high conductivity has small flow noise, but it is difficult to measure the flow velocity of a minute flow. Further, the electromagnetic flowmeter requires large energy for applying a magnetic field, and thus consumes a large amount of power.

Further, it is necessary to bend and assemble the components in accordance with the shape of the cylindrical measuring tube 61, and as a result, the productivity of the electromagnetic flowmeter is reduced.

A first object of the present invention is to provide an electromagnetic flowmeter which can reliably measure a flow rate of a fluid to be measured having a low electric conductivity or a minute flow, improve the performance of the flow measurement, and consume less power. To provide.

[0014] A second object of the present invention is to provide an electromagnetic flowmeter capable of improving productivity.

[0015]

In order to achieve the first object, an electromagnetic flowmeter according to the present invention has a measurement section in which a cross section of an inner wall of a measurement section is flattened and a fluid to be measured flows inside the measurement section. A tube, a coil arranged on the flattened surface of the measuring tube and having a reduced interval, and applying a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measuring tube; And a pair of electrodes that take out the electromotive force generated by the movement of the fluid to be measured in the magnetic field, and a measurement tube, a coil, and a core and return magnet that surround the electrodes. And a yoke forming a path.

Therefore, in the electromagnetic flowmeter according to the first aspect of the present invention, the Faraday's law of electromagnetic induction e = BD
From v × 10 ⁻⁴ , the magnetic flux density and the moving speed do not change and the width of the fluid to be measured is increased, so that the electromotive force is increased. As a result, the fluid to be measured having a low electrical conductivity has a large electromotive force, so that the fluid is hardly affected by flow noise, and the flow velocity of the fluid to be measured can be measured with good performance. Also, by flattening the cross section of the inner wall of the measuring part of the measuring tube, the distance for applying the magnetic field is shortened, so when measuring the flow velocity of the fluid to be measured having high conductivity, the magnetic field is applied by reducing the magnetic flux density. Energy can be reduced and power consumption can be reduced.

In the electromagnetic flowmeter according to the second aspect of the present invention, the inner wall section of the measuring section is made elliptical, and the space between the measuring pipe and the measuring pipe through which the fluid to be measured flows is made shorter. And a coil that applies a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measurement tube, and a coil that is disposed opposite to the elliptical surface of the measurement tube that has a long interval, and It comprises a pair of electrodes for extracting an electromotive force generated by the movement of the measurement fluid, a measurement tube, a coil, and a yoke which is arranged so as to surround the electrode and forms a coil core and a return path.

Therefore, in the electromagnetic flow meter according to the second aspect of the present invention, the Faraday's law of electromagnetic induction e = BD
From v × 10 ^-4 , the magnetic flux density and the moving speed do not change and the width of the fluid to be measured is increased, so that the electromotive force is increased. As a result, the fluid to be measured having a low electrical conductivity has a large electromotive force, so that the fluid is hardly affected by flow noise, and the flow velocity of the fluid to be measured can be measured with good performance. Also, by making the cross section of the inner wall of the measuring section of the measuring tube elliptical, the distance over which the magnetic field is applied becomes shorter.When measuring the flow velocity of the fluid to be measured having high conductivity, the magnetic field is reduced by reducing the magnetic flux density. The applied energy can be reduced, and the power consumption can be reduced. Furthermore, by making the inner wall cross section of the measuring portion of the measuring tube elliptical, the measuring tube can be made resistant to pressure.

Further, in the electromagnetic flowmeter according to the invention, the inner wall cross section of the measuring section is made rectangular, and the inside of the measuring pipe through which the fluid to be measured flows is made rectangular, and the surface of the measuring pipe is made rectangular and the interval is shortened. And a coil for applying a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measurement tube, and a coil arranged to face the rectangular and long-spaced surface of the measurement tube. It comprises a pair of electrodes for extracting an electromotive force generated by the movement, a measurement tube, a coil, and a yoke arranged so as to surround the electrode and forming a coil core and a return path.

Therefore, in the electromagnetic flowmeter according to the third aspect of the present invention, the Faraday's law of electromagnetic induction e = BD
From v × 10 ^-4 , the magnetic flux density and the moving speed do not change and the width of the fluid to be measured is increased, so that the electromotive force is increased. As a result, the fluid to be measured having a low electrical conductivity has a large electromotive force, so that the fluid is hardly affected by flow noise, and the flow velocity of the fluid to be measured can be measured with good performance. In addition, by making the inner wall cross section of the measurement part of the measurement tube rectangular, the distance for applying the magnetic field is shortened. Therefore, when measuring the flow velocity of the fluid to be measured having high conductivity, the magnetic field is applied by reducing the magnetic flux density. Energy can be reduced and power consumption can be reduced. Further, by making the inner wall cross section of the measuring portion of the measuring tube rectangular, it is possible to easily make the measuring tube.

According to a fourth aspect of the present invention, there is provided the electromagnetic flow meter according to any one of the first to third aspects, wherein the inner wall of the measuring section of the measuring pipe is cut off. The area is smaller than the entrance.

Therefore, in the electromagnetic flowmeter according to the present invention, the inner wall cross-sectional area of the measuring section of the measuring tube is made smaller than the entrance and exit, so that Faraday's law of electromagnetic induction e = BD From v × 10 ⁻⁴ , the magnetic flux density does not change, the width of the fluid to be measured is the same or larger, and the moving speed is increased, so that the electromotive force is further increased. As a result, the electromotive force of the fluid to be measured having a low conductivity is further increased, so that the fluid is less affected by the flow noise, and the flow velocity of the fluid to be measured can be measured with higher performance. In addition, by setting the cross-sectional area of the inner wall of the measuring section of the measuring tube to be smaller than that of the entrance and exit, the distance over which the magnetic field is applied is further shortened. , The energy for applying the magnetic field can be further reduced, and the power consumption can be further reduced.

On the other hand, in order to achieve the second object,
An electromagnetic flowmeter according to the invention according to claim 5, wherein the cross section of the outer wall of the measuring section is quadrangular, and the inside is arranged on both the measuring pipe through which the fluid to be measured flows and the plane crossing the measuring pipe. A coil that provides a magnetic field in a direction substantially perpendicular to the tube axis direction and a coil that is disposed opposite to both surfaces in a direction substantially perpendicular to the coil of the measurement tube. A pair of electrodes to be taken out, a measurement tube, a coil, and arranged to surround the electrodes,
And a yoke forming a return magnetic path.

Therefore, in the electromagnetic flow meter according to the present invention, since the cross-section of the outer wall of the measuring section of the measuring tube is made rectangular, the components of the electromagnetic flow meter are attached to a flat surface, so that the curved portion is curved. Processing becomes unnecessary, and the adhesion to the measurement tube can be improved. Also, the components of the electromagnetic flowmeter can be easily packed. This reduces the number of processing steps when producing electromagnetic flow meters,
Since the assembling accuracy is improved and the transportation efficiency is improved, productivity can be improved.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view showing an example of the configuration of a measuring section of an electromagnetic flowmeter according to the present embodiment.

As shown in FIG. 1, the electromagnetic flow meter according to the present embodiment has a measurement section 11 in which the inner wall of the measuring section is flattened to have a cross-sectional area substantially equal to that of the entrance and exit.
A pair of coils 12 arranged on a flattened surface of the measuring tube 11 at a reduced interval to apply a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measuring tube 11;
A pair of electromagnetic 13 for taking out an electromotive force generated by movement of a fluid to be measured in a magnetic field, a measurement tube 11, and a coil 1
2, and a yoke 14 which is arranged to surround the electrode 13 and forms a core of the coil 12 and a return path.

Next, in the electromagnetic flowmeter of the present embodiment configured as described above, the inner wall of the measuring section of the measuring tube 11 is made flat to have the same cross-sectional area as the entrance and exit, so that the Faraday electromagnetic Guidance law e = BDV x 1
Since the magnetic flux density B and the moving speed v do not change from 0 ^-4 and the width D of the fluid to be measured increases, the electromotive force e increases.

As a result, the fluid to be measured having a low conductivity has a large electromotive force, so that the fluid is hardly affected by flow noise, and the flow velocity of the fluid to be measured can be measured with good performance. Further, since the inner wall cross section of the measuring portion of the measuring tube 11 is flattened to have substantially the same cross sectional area as the entrance and exit, the distance for applying a magnetic field is shortened. By reducing the density B, the energy for applying a magnetic field can be reduced, and the power consumption can be reduced.

As described above, in the electromagnetic flowmeter according to the present embodiment, the inner wall of the measuring section of the measuring tube 11 is made flat so as to have substantially the same cross-sectional area as the entrance and exit, so that the width of the fluid to be measured is Since D becomes large and the distance over which the magnetic field is applied becomes short, the flow rate measurement performance of the fluid to be measured having a low conductivity or a small flow can be reliably measured to improve the performance of the flow rate measurement, and the power consumption is reduced. It becomes possible.

(Second Embodiment) FIG. 2 is a sectional view showing an example of the configuration of a measuring section of an electromagnetic flowmeter according to the present embodiment.

As shown in FIG. 2, the electromagnetic flow meter according to the present embodiment has an elliptical inner wall cross section having substantially the same cross-sectional area as the entrance and exit, and a measurement pipe 21 through which the fluid to be measured flows.
A pair of coils 22 arranged on an elliptical surface of the measurement tube 21 having a reduced interval and applying a magnetic field to the fluid to be measured in a direction substantially orthogonal to the tube axis direction of the measurement tube 21;
It is arranged opposite to the elliptical shape of 1 and the surface where the interval is long,
A pair of electromagnetic waves 23 for extracting an electromotive force generated by the movement of the fluid to be measured in the magnetic field, and a pair of electromagnetic waves 23 are arranged so as to surround the measurement tube 21, the coil 22, and the electrode 23, and form a core and a return path of the coil 22. And the yoke 24 which is formed.

Next, in the electromagnetic flow meter according to the present embodiment configured as described above, the inner wall of the measuring section of the measuring tube 21 is made elliptical to have substantially the same cross-sectional area as the entrance and exit, so that the Faraday Electromagnetic induction law e = BDVx
From 10 ^-4 , the magnetic flux density B and the moving speed v do not change, and the width D of the fluid to be measured increases, so that the electromotive force e increases.

Thus, the fluid to be measured having a low conductivity has a large electromotive force, so that the fluid is hardly affected by flow noise, and the flow velocity of the fluid to be measured can be measured with good performance. Further, since the inner wall cross section of the measuring section of the measuring tube 21 is made elliptical and has substantially the same cross sectional area as the entrance and exit, the distance for applying a magnetic field is shortened. Therefore, when measuring the flow velocity of the fluid to be measured having high conductivity, By reducing the magnetic flux density B, the energy for applying a magnetic field can be reduced, and power consumption can be reduced.

Further, by making the inner wall cross section of the measuring portion of the measuring tube 21 elliptical, the measuring tube 21 can be made resistant to pressure.

As described above, in the electromagnetic flow meter according to the present embodiment, the inner wall of the measuring section of the measuring tube 21 is made elliptical so as to have substantially the same cross-sectional area as the entrance and exit. Since the width D increases and the distance over which the magnetic field is applied decreases, the flow rate measurement performance can be improved by reliably measuring the flow rate of the fluid to be measured having a low conductivity or a minute flow, and the power consumption can be reduced. And the pressure of the measuring tube 21 can be increased.

(Third Embodiment) FIG. 3 is a sectional view showing an example of a configuration of a measuring section of an electromagnetic flowmeter according to the present embodiment.

As shown in FIG. 3, the electromagnetic flow meter according to the present embodiment has a rectangular cross section of the inner wall of the measuring section, which has substantially the same cross sectional area as the entrance and exit, and a measuring pipe 31 inside which the fluid to be measured flows.
A pair of coils 32 arranged on a rectangular surface of the measuring tube 31 with a short interval and applying a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measuring tube 31;
It is arranged opposite to the surface where the interval has become longer by making one rectangle,
A pair of electromagnetic waves 33 for extracting an electromotive force generated by the movement of the fluid to be measured in the magnetic field, and a pair of electromagnetic waves 33 are arranged so as to surround the measurement tube 31, the coil 32, and the electrode 33, and form a core and a return path of the coil 32. And the yoke 34 to be used.

Next, in the electromagnetic flowmeter according to the present embodiment configured as described above, the inner wall of the measuring section of the measuring tube 31 is made rectangular and has substantially the same cross-sectional area as the entrance and exit, so that the Faraday electromagnetic Guidance law e = BDVx
From 10 ^-4 , the magnetic flux density B and the moving speed v do not change, and the width D of the fluid to be measured increases, so that the electromotive force e increases.

As a result, the fluid to be measured having a low conductivity has a large electromotive force, so that the fluid is hardly affected by flow noise, and the flow velocity of the fluid to be measured can be measured with good performance. In addition, since the inner wall of the measuring section of the measuring tube 31 has a rectangular cross-section and has substantially the same cross-sectional area as the entrance and exit, the distance over which the magnetic field is applied becomes shorter. By reducing the density B, the energy for applying a magnetic field can be reduced, and the power consumption can be reduced.

As described above, in the electromagnetic flowmeter of the present embodiment, the inner wall of the measuring section of the measuring tube 31 has a rectangular cross-section and has substantially the same cross-sectional area as the entrance and exit, so that the width of the fluid to be measured is Since D becomes large and the distance over which the magnetic field is applied becomes short, the flow rate measurement performance of the fluid to be measured having a low conductivity or a small flow can be reliably measured to improve the performance of the flow rate measurement, and the power consumption is reduced. This makes it possible to make the measuring tube 31 easier.

(Fourth Embodiment) FIG. 4 is a sectional view showing an example of the configuration of a measuring section of an electromagnetic flowmeter according to the present embodiment.

As shown in FIG. 4, the electromagnetic flow meter according to the present embodiment has a flat cross section of the inner wall of the measuring section to have a smaller cross sectional area than the entrance and exit, and the inside of the measuring pipe 41 through which the fluid to be measured flows.
A pair of coils 42 arranged on the flattened surface of the measuring tube 41 and having a reduced interval to apply a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measuring tube 41;
A pair of electromagnetic 43 for taking out an electromotive force generated by the movement of the fluid to be measured in the magnetic field, a measuring tube 41, and a coil 4.
2, and a yoke 44 that is arranged so as to surround the electrode 43 and forms a core of the coil 42 and a return path.

Next, in the electromagnetic flow meter according to the present embodiment configured as described above, the inner wall of the measuring portion of the measuring tube 41 is made flat to have a smaller cross-sectional area than the entrance, so that the Faraday electromagnetic Guidance law e = BDVx
From 10 ^-4 , the magnetic flux density B does not change and the width D of the fluid to be measured is
Are the same or larger, and the moving speed v becomes faster, so that the electromotive force e is further increased as compared with the first embodiment.

As a result, the fluid to be measured having a low conductivity has a larger electromotive force, so that the fluid is less affected by flow noise, and the flow velocity of the fluid to be measured can be measured with higher performance. Further, since the cross-sectional area of the inner wall of the measuring portion of the measuring tube 41 is smaller than that of the entrance and exit, the distance for applying a magnetic field is further shortened. By reducing the density, the energy for applying the magnetic field can be further reduced, and the power consumption can be further reduced as compared with the first embodiment.

As described above, in the electromagnetic flowmeter according to the present embodiment, the inner wall of the measuring section of the measuring tube 41 is made flat to have a smaller sectional area than the entrance and exit, so that the movement of the fluid to be measured is performed. Since the speed is increased, the flow rate measurement performance of the fluid to be measured having a low conductivity or a minute flow can be more reliably measured as compared with the first embodiment, and the performance of the flow rate measurement can be further improved. At the same time, power consumption can be further reduced.

(Modification) In the electromagnetic flowmeter of the present embodiment, the inner wall section of the measuring section of the measuring tube is different from the electromagnetic flowmeter of the first embodiment in which the inner wall section of the measuring section of the measuring pipe is flattened. Is described as having a smaller cross-sectional area than the entrance and exit. However, the present invention is not limited to this. In the electromagnetic flow meter according to the second or third embodiment in which the inner wall cross section of the measuring portion of the measuring tube is made elliptical or rectangular. Even when the cross section of the inner wall of the measuring section of the measuring tube is smaller than the entrance and exit, the same operation and effect as in the case of the present embodiment can be obtained.

(Fifth Embodiment) FIG. 5 is a sectional view showing an example of the configuration of a measuring section of an electromagnetic flowmeter according to the present embodiment.

As shown in FIG. 5, the electromagnetic flow meter according to the present embodiment has a rectangular section on the outer wall of the measuring section, and has a measuring pipe 51 inside which the fluid to be measured flows and a plane crossing the measuring pipe 51. A pair of coils 52 arranged to apply a magnetic field to the fluid to be measured in a direction substantially perpendicular to the tube axis direction of the measurement tube 51;
A pair of electrodes 53 disposed opposite to both planes in a direction substantially orthogonal to the coil 52 of the measurement tube 51 to extract an electromotive force generated by the movement of the fluid to be measured in the magnetic field;
It is arranged so as to surround the measurement tube 51, the coil 52, and the electrode 53, and includes a core of the coil 52 and a yoke 54 forming a return path.

Next, in the electromagnetic flow meter according to the present embodiment configured as described above, since the cross section of the outer wall of the measuring section of the measuring tube 51 is rectangular, the components of the electromagnetic flow meter can be arranged with respect to a plane. Since it is attached, bending work is not required, and the adhesion to the measurement tube 51 can be improved.

Further, the components of the electromagnetic flowmeter can be easily packed.

This reduces the number of processing steps when producing the electromagnetic flow meter, improves the assembly accuracy, and improves the transport efficiency, so that the productivity can be improved.

As described above, in the electromagnetic flow meter according to the present embodiment, since the outer wall section of the measuring section of the measuring tube 51 is made rectangular, the components of the electromagnetic flow meter are mounted on a flat surface. Therefore, the bending process is not required, the adhesion to the measuring tube can be improved, and the components of the electromagnetic flowmeter can be easily packed.
Thereby, when manufacturing the electromagnetic flow meter, the number of processing steps is reduced, assembling accuracy is improved, and transportation efficiency is improved, so that productivity can be improved.

[0054]

As described above, according to the present invention, the flow rate measurement performance can be improved by reliably measuring the flow rate of a fluid to be measured having a low conductivity or a minute flow, and the power consumption can be reduced. An electromagnetic flow meter can be provided.

Further, according to the present invention, it is possible to provide an electromagnetic flowmeter capable of improving productivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a measuring unit of an electromagnetic flowmeter according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the measuring section of the electromagnetic flow meter according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the measuring section of the electromagnetic flow meter according to the present invention.

FIGS. 4A and 4B are a cross-sectional view and a vertical cross-sectional view illustrating a fourth embodiment of the measuring unit of the electromagnetic flowmeter according to the present invention.

FIG. 5 is a sectional view showing a fifth embodiment of the measuring section of the electromagnetic flow meter according to the present invention.

FIG. 6 is a cross-sectional view illustrating a configuration example of a measurement unit of a conventional electromagnetic flowmeter.

FIG. 7 is a conceptual diagram showing the measurement principle of a conventional electromagnetic flow meter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Measuring tube 12 ... Coil 13 ... Electrode 14 ... Yoke 21 ... Measuring reed 22 ... Coil 23 ... Electrode 24 ... Yoke 31 ... Measuring tube 32 ... Coil 33 ... Electrode 34 ... Yoke 41 ... Measuring tube 42 ... Coil 43 ... Electrode 44 ... Yoke 51 ... Measurement tube 52 ... Coil 53 ... Electrode 54 ... Yoke 61 ... Measurement tube 62 ... Coil 63 ... Electrode 64 ... Yoke 71 ... Magnetic east density 72 ... Movement speed 73 ... Conductor width 74 ... Electromotive force.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takuya Iijima 1 Toshiba-cho, Fuchu-shi, Tokyo F-term in the Fuchu factory of Toshiba Corporation (reference) 2F035 BA01

Claims (5)

[Claims] 1. A measuring pipe in which a cross section of an inner wall of a measuring section is flattened and a fluid to be measured flows inside the measuring pipe; A coil for applying a magnetic field in a direction substantially perpendicular to the tube axis direction, and an electromotive force generated when the fluid to be measured moves in the magnetic field, the coil being arranged to face the flattened surface of the measurement tube at a longer interval. An electromagnetic flowmeter comprising: a pair of electrodes to be taken out; and a yoke arranged to surround the measurement tube, the coil, and the electrode, and to form a core and a return path of the coil. 2. A measuring pipe having an elliptical inner wall cross section and a measuring pipe through which a fluid to be measured flows, and an elliptical surface of the measuring pipe arranged at a shorter interval to measure the fluid to be measured. A coil for applying a magnetic field in a direction substantially perpendicular to the tube axis direction of the tube; and a coil which is disposed opposite to the elliptical surface of the measurement tube having a longer interval, and which is generated when the fluid to be measured moves in the magnetic field. An electromagnetic flowmeter comprising: a pair of electrodes for extracting an electromotive force; and a yoke arranged to surround the measurement tube, the coil, and the electrode, and to form a core and a return path of the coil. . 3. The measuring section has a rectangular inner wall cross section, the inside of which is arranged on a measuring pipe through which a fluid to be measured flows, and a rectangular section of the measuring pipe, which is disposed on a surface with a short interval. A coil that applies a magnetic field in a direction substantially perpendicular to the tube axis direction; and a coil that is disposed to face a rectangular and long-spaced surface of the measurement tube, and generates an electromotive force generated when the fluid to be measured moves in the magnetic field. An electromagnetic flowmeter comprising: a pair of electrodes to be taken out; and a yoke arranged to surround the measurement tube, the coil, and the electrode, and to form a core and a return path of the coil. 4. The method according to claim 1, wherein
3. The electromagnetic flowmeter according to claim 1, wherein the cross-sectional area of the inner wall of the measuring section of the measuring tube is smaller than that of the entrance. 5. The measuring section has a rectangular outer wall cross section, and has a measuring pipe through which a fluid to be measured flows, and is disposed on both planes crossing the measuring pipe. A coil for providing a magnetic field in a direction perpendicular to the coil, and a pair of electrodes disposed opposite to both planes in a direction substantially perpendicular to the coil of the measurement tube and for extracting an electromotive force generated by movement of the fluid to be measured in the magnetic field And a yoke arranged to surround the measuring tube, the coil, and the electrode, and forming a core and a return path of the coil.