JPH0226031Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an electromagnetic flowmeter, and particularly to a so-called liningless electromagnetic flowmeter in which a lining is not provided inside a conductive conduit.

<Prior Art> FIG. 1 shows the configuration of a conventional electromagnetic flowmeter that is the basis of the improvement of the present invention. In the figure, 1 is a conductive conduit through which a fluid to be measured flows. A measuring electrode 2a for detecting a signal voltage generated in the fluid is connected to an insulating ring 3a in the conductive conduit 1.
has been fixed through. There are also a measuring electrode 2b and an insulating ring 3b on the back side of the paper, but since they have the same configuration, the description on the b side is omitted. In the following description, illustration of the b side will be omitted and only the reference numeral will be used. The tube axis direction at the center of the conductive conduit 1 is the z-axis, and the direction connecting the measurement electrodes 2a and 2b is the x-axis.
Let the axis orthogonal to each of the axis and the z-axis be the y-axis. A magnetic field is applied in a direction parallel to the y-axis. 4a and 4b are tube potential electrodes that detect the potential of the conductive conduit 1 near the measurement electrodes 2a and 2b. 5a, 5b are the voltages of these measurement electrodes 2a, 2b and tube potential electrodes 4a, 4.
This is an amplifier which supplies current from its output ends 6a, 6b to power supply electrodes 7a, 7b fixed to the conductive conduit 1 so that the voltage difference therebetween becomes zero. 8 is a ground electrode, and power supply electrodes 7a, 7
The current flowing into b flows into the conductive conduit 1 and flows out from the ground electrode 8 while forming a potential distribution in this portion. This potential distribution exhibits approximately the same potential distribution as the potential distribution in the fluid to be measured near the conductive conduit 1, and achieves the so-called liningless purpose. The power supply electrodes 7a, 7b are arranged parallel to the z-axis, slightly apart from the measurement electrodes 2a, 2b in the circumferential direction of the conductive pipe 1, and are fixed to the conductive pipe 1. Due to the structure of the power supply electrodes 7a and 7b, the current flowing out from the power supply electrodes flows along the pipe wall of the conductive conduit 1 approximately parallel to the y-axis, resulting in a two-dimensional potential including the x-y axis. form a distribution. Further, when this potential distribution is viewed in a cross section including the y-z axis, it is a trapezoidal potential distribution.

FIG. 2 is a diagram showing a second conventional example.
In the following description, components having the same functions as those in FIG. 1 will be denoted by the same reference numerals, and the description will be omitted as necessary. The difference in FIG. 2 from FIG. 1 is that the power supply electrodes 9a, 9b
The point is that the shape is annular with the measurement electrodes 2a and 3a at the center. Therefore, the feeding electrode 9
The current flowing from a, 9b to the ground electrode 8 flows in the radial direction of the ring, and then becomes radial. Therefore, a potential distribution corresponding to this is formed in the conductive conduit 1.

By the way, in order to accurately achieve the purpose of no lining, it is necessary to create a conductive pipe with the same potential distribution as that which occurs in the fluid to be measured when the conductive pipe 1 is lined with an insulating material on its inner surface. The conductive conduit 1 must be formed in such a manner that no current flows between the conductive conduit 1 and the fluid to be measured. However, in the conventional embodiment shown in FIG. 1, the potential distribution is such that the potential simply drops in the conductive conduit from the power supply electrode to the ground electrode, and the potential distribution is simply trapezoidal in the z-axis direction. It merely forms a distribution.
In the conventional embodiment shown in FIG. 2 as well, a radial potential distribution is simply formed from the annular power supply electrode toward the ground electrode. Therefore, the first
Neither in the illustrated embodiment nor in the embodiment shown in FIG. 2 is an accurate potential distribution formed in the conductive conduit.
For this reason, there is a drawback that errors occur when the conductivity of the fluid to be measured changes.

<Purpose of the invention> In view of the above-mentioned prior art, the present invention aims to improve the shape of the power supply electrode and obtain a highly accurate electromagnetic flowmeter that is not affected by the conductivity of the fluid to be measured.

<Configuration of the invention> The configuration of the present invention to achieve this objective is to form a potential distribution between a measurement electrode for detecting a signal voltage generated inside a conductive conduit through which a fluid to be measured flows, and the conductive conduit. an electromagnetic flowmeter, the electromagnetic flowmeter having a power supply electrode, and supplying current to the power supply electrode so that the difference between the voltage detected by the measurement electrode and the voltage of the conductive conduit near the measurement electrode becomes zero. The power supply electrode is characterized in that the shape of the power supply electrode is an ellipse that is flattened in a direction perpendicular to the tube axis of the conductive conduit.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 3 shows the potential distribution generated in the fluid in a cross section including the x-y axis when the fluid flows when the conductive conduit 1 is provided with an insulating lining. -1, -2, - written around the pipe line
The numerical values 5, +1, +2, and +5 indicate the ratio of potential distribution of each equipotential surface generated in the fluid and its polarity. Figure 4 shows x-z under the same conditions as Figure 3.
It shows the potential distribution generated in the fluid in the cross section of the pipe including the shaft. A flat elliptical equipotential surface is formed in the x-axis direction with the measurement electrode 2a or 2b as the center. FIG. 5 is a spatial perspective view of FIGS. 3 and 4. As can be seen from this figure, the line of intersection between the equipotential surface and the pipe line tends to move away from the yz plane when z is large.

Based on the above findings, the present invention attempts to precisely achieve the purpose of eliminating lining by shaping the power supply electrode along the above-mentioned intersection line and disposing it near the measurement electrode. Figure 6 is the first diagram related to the present invention.
FIG. As shown in the figure, the shapes of the power supply electrodes 10a and 10b are as follows:
The conductive conduit 1 is divided into upper and lower parts with 2b as the center, and is arranged along the shape of the intersection line in the vicinity of the measurement electrodes 2a and 2b in FIG. Specifically, its shape is an ellipse that is flat in the y-axis direction. The upper and lower divided power supply electrodes 10a and 10b are connected to each other by lead wires 11a and 11b in order to maintain the same potential. Since the power supply electrode has a shape along the equipotential surface, the same potential distribution is formed in the fluid as that which occurs in the fluid when the inner surface of the conductive pipe 1 is insulated, resulting in a highly accurate liningless electromagnetic flowmeter. is obtained.

FIG. 7 shows a second embodiment of the invention. The difference from the embodiment shown in FIG. 6 is that the power supply electrodes 12a, 12b
The shape is the same as that of an ellipse that is flattened in the y-axis direction, but the difference is that it is not divided into two parts but is formed as one piece and fixed to the conductive conduit 1.
With such a configuration, it is possible to get closer to the equipotential surface around the conductive conduit in the fluid.

FIG. 8 shows a third embodiment of the invention. The configuration of the embodiment shown in this figure is a case where a plurality (two) of flat elliptical power supply electrodes are provided in the conductive conduit in the y-axis direction. The voltages at the output terminals 6a, 6b of the amplifiers are directly fed to the inner feed electrodes 13a, 13b, and the voltages at the output ends 6a, 6b of the amplifiers are fed to the outer feed electrodes 14a, 14b.
The output voltage of the conductive pipe 1 is appropriately divided by the resistors R ₁ and R ₂ and then supplied to form a more accurate potential distribution. Even if there are a plurality of power supply electrodes, the output voltage of the amplifier may be appropriately divided into a plurality of electrodes and then supplied.

<Effects of the invention> As specifically explained above in conjunction with the embodiments, according to the present invention, it is possible to form a potential distribution in the conductive pipe line that matches the potential distribution occurring in the fluid, so that the electrical conductivity of the fluid increases. , the flow rate can be accurately measured without being affected by contact resistance between the fluid and the conductive pipe.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of a conventional electromagnetic flowmeter, Fig. 2 is a block diagram showing another embodiment of a conventional electromagnetic flowmeter, and Fig. 3 is a block diagram showing an x-y plane that occurs in a fluid. Figure 4 shows the potential distribution of x generated in the fluid.
-A diagram showing the potential distribution in the z plane, FIG. 5 is a perspective view showing the potential distribution generated in the fluid, FIG. 6 is a configuration diagram showing the first embodiment of the electromagnetic flowmeter of the present invention, and FIG. 7 8 is a block diagram showing a second embodiment of the present invention, and FIG. 8 is a block diagram showing a third embodiment of the present invention. 1... Conductive conduit, 2a, 2b... Measurement electrode,
4a, 4b...tube potential electrode, 5a, 5b...amplifier, 7a, 7b...power supply electrode, 8...ground electrode,
9a, 9b, 10a, 10b, 12a, 12b,
13a, 13b, 14a, 14b...power supply electrodes.

Claims (1)

[Scope of utility model registration request] A measurement electrode for detecting a signal voltage generated inside a conductive conduit through which a fluid to be measured flows, and a power supply electrode for forming a potential distribution in the conductive conduit, and the voltage detected by the measurement electrode and In an electromagnetic flowmeter in which a current is supplied to the power supply electrode so that the difference between the voltage of the conductive conduit near the measurement electrode and the voltage of the conductive conduit becomes zero, the shape of the power supply electrode is adjusted to the tube axis of the conductive conduit. An electromagnetic flowmeter characterized by having an elliptical shape that is flattened in the direction perpendicular to the direction.