JPS597931B2 - electromagnetic flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a pair of opposing electrodes that directly sandwich at least a portion of a conductive fluid, and a magnetic circuit that generates a magnetic flux that intersects both a straight line and a flow passing through both electrodes. The present invention relates to an electromagnetic flowmeter that calculates flow velocity based on the voltage generated between both electrodes due to the magnetic flux of the magnetic circuit and the flow of fluid.

The purpose of this electromagnetic flowmeter is to satisfy the conditions that there is no significant zero point fluctuation due to the electrochemical action of the electrodes, and that the zero point can be easily checked even while the fluid is flowing, while also minimizing power consumption. , the excitation current applied to the excitation coil is intermittent, instantaneous, and alternately in opposite directions, and the magnetic circuit maintains a residual magnetic flux and fluid flow between the two electrodes while the excitation current does not flow. The applicant previously filed a patent application for an electromagnetic flowmeter that calculates the flow velocity based on the voltage generated between the two.

By the way, in this case, the effect that the change in the resistance value of the excitation wire ring due to the change in the environmental temperature has on the magnitude of the residual magnetic flux is as follows.
It can be made extremely small by connecting a temperature compensation resistor with a smaller resistance temperature coefficient and a larger resistance value in series with the excitation wire ring, but if the constituent material of the magnetic circuit is not selected appropriately, the excitation current cannot be kept constant. Even when equipped with a means for changing the temperature, the residual magnetic flux fluctuates due to changes in the environmental temperature, resulting in an error in the measured flow velocity.

In view of this, it is an object of the present invention to realize an intermittent reversal instantaneous excitation electromagnetic flowmeter that does not have the above-mentioned drawbacks. This electromagnetic flowmeter is characterized in that it is configured by connecting in series a yoke made of a high permeability material with a high residual magnetic flux and a magnet body made of a permanent magnet material.

FIG. 1 shows a cross section perpendicular to the flow of a conductive 5 fluid for one embodiment of the invention. The fluid conduit 1 is
It is non-magnetic and non-conductive over a considerable range in the longitudinal direction near this cross section. There is a pair of electrodes 2a, 2b exposed inside the conduit 1 and facing each other so as to directly sandwich at least a portion of the fluid flow. Each electrode 2a, 2b is connected via a conductor portion that penetrates the wall of the conduit 1 in a watertight manner to a flow rate calculation device 3 that calculates the flow rate based on the voltage between the electrodes 2a, 2b. A yoke 5a with magnetic poles 4a and 4b sandwiching the pipe 1
! 55b is made of a high magnetic permeability material with high magnetic permeability and low residual magnetic flux, such as electromagnetic soft iron or silicon steel plate, and the electrodes 4a,
The magnetic flux generated between the magnetic poles 2a and 2b intersects both the straight line passing through the magnetic poles 2a and 2b and the fluid flow.

The yokes 5a and 5b have a magnet body 6 at the end opposite to the magnetic poles 4a and 4b made of a permanent magnet material such as cast Alnico 1, which does not have a very large holding force but has a rapid rise D of magnetic flux and is quick to saturate. They are sandwiched together to form one magnetic circuit 4 as a whole.
An excitation wire ring 7 for exciting the magnetic circuit 4 is wound around the outer periphery of the magnet body 6, and the wire diameter is made thick and the total resistance value is made small.

An excitation device 8 is connected to the excitation wire ring 7, which supplies excitation current intermittently, instantaneously each time, and alternately in opposite directions. The relationship with the magnetic flux generated when the permanent magnet material constituting the magnet body 6 is placed in a magnetic field that changes back and forth with a sufficient strength width is the second
It is assumed that the change occurs as shown in the solid line diagram in the figure.

Next, in the magnetic circuit 4 of the embodiment shown in FIG.
Since the magnetic permeability of 5b is 8,000 to 12,000 times higher than that of the gap between the magnetic poles 4a and 4b, the magnetomotive force generated in this gap by the current of the excitation wire ring 7 is generated between the end faces of the magnet body 6. It is practically equivalent to

Therefore, the relationship between the magnetic flux of the magnet 6 and the magnetic field caused by it is such that the versiance (Pg) between the magnetic poles 4a and 4b is, for example, Pm=Pg><1m/Sm (where 1m, Sm is the length of the magnet 6). Using the relational expression (S, cross-sectional area), the magnetic body 6
It is determined by the value converted to the Persiassian coefficient (Pm). Since the perceance between the magnetic poles 4a and 4b is determined geometrically, the relationship between the magnetic flux of the magnet body 6 and the magnetic field caused by it is constant, and can be represented by the slope line P--P in FIG. When the change in the magnetic field H generated in the magnet body 6 by the current flowing through the excitation wire ring 7 by the excitation device 8 remains within the range (+h to -hl) in FIG. 2, the magnetic field H and the magnet body 6 change. The relationship with the magnetic flux changes along the diagram Q-q shown by the horizontal line in Figure 2, but beyond that range (+H
-Hl), the change is made along the broken line R-P-k-pi.

Therefore, when the excitation current of the excitation wire ring 7 disappears, the line diagram R-P-k-Y and the slope line P1? P or ν, which is the intersection with
The residual magnetic flux becomes B or -B'. If the excitation currents in both directions are made equal in magnitude, B=W. Also, the above relational expression P
m=Pg>(1m/Sm As is clear from The absolute value becomes larger.

In this way, in the electromagnetic flowmeter of the present invention, the magnetic circuit 4 is constructed by connecting in series the yokes 5a and 5b made of a high magnetic permeability material with high magnetic permeability and low residual magnetic flux, and the magnet body 6 made of a permanent magnetic material. Because of the connected structure, the influence of changes in the environmental temperature on the residual magnetic flux is substantially determined only by the magnet body 6, and in the permanent magnet material that is the material of the magnet body 6, the residual magnetic flux changes depending on the environmental temperature. Since the fluctuation caused by the change is extremely small, for example, 1 (0.06 to 0.02)'F6/°C, there is naturally almost no fluctuation in the magnetic flux in the gap between the magnetic poles 4a and 4b. The above-mentioned disadvantage that changes in environmental temperature cause errors in the measured flow rate can be eliminated.

In another embodiment, whose longitudinal section is shown in FIG. 3 and whose cross section is shown in FIG. The perseverance of the magnetic circuit 4 is increased, and the two magnet bodies 6a, 6b and 2
Excitation wire rings 7a, 7b are provided, and the yoke is connected to the electrodes 4a, 4.
b and one end of the magnet bodies 6a, 6b and the portion 5a between each
, 5b, and a portion 5 between the other ends of the magnet bodies 6a, 6b.

These parts, together with the leads of the excitation coil 7a97b and the electrodes 2a, 2b, are held in position by the stuffed toy at the same time as the conduit 1 is molded of plastic. An excitation device 8 connected to excitation wire rings 7a and 7b, a flow rate calculation device 3 connected to electrodes 2a and 2b, a processing device 9 containing a power source battery, a transmitting device, etc. are attached to the upper side of the conduit 1. . The conduit 1 has metal caps 1 on both ends.
0 is tightly screwed in in an airtight manner so as to be connected to the piping by the screw of the base 10, and has enough strength to withstand longitudinal tensile force in the installed state.

In this way, the magnet bodies 6a, 6b of the magnetic circuit 4 and the yoke 5
, 5a, 5b, the overall size can be reduced while obtaining sufficient residual magnetic flux, so the overall price can be kept low.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of one embodiment of the present invention, and Fig. 2 is a cross-sectional view of an embodiment of the present invention.
Diagrams for explaining the residual magnetism of the magnet body in the embodiment shown in the figure, A-A of embodiments different from those in FIGS. 3 and 4, respectively.
They are a longitudinal cross-sectional view and a BB transverse cross-sectional view. 2a, 2b... Electrode, 4... Magnetic circuit, 7, 7a,
7b... Excitation wire ring, 5, 5a, 5b... Yoke, 6,
6a, 6b... magnet bodies.

Claims (1)

[Claims] 1. A pair of opposing electrodes that directly sandwich at least a portion of the flow of a conductive fluid, a magnetic circuit that generates a magnetic flux that crosses both the straight line passing through the electrodes and the flow, and exciting this magnetic circuit. This is caused by the residual magnetic flux and fluid flow maintained by the magnetic circuit when the excitation current is not flowing, and the excitation current is passed through the excitation wire intermittently, instantaneously, and alternately in opposite directions. In an electromagnetic flowmeter that calculates the flow velocity based on the voltage generated between both electrodes, the magnetic circuit is composed of a yoke made of a high permeability material with high magnetic permeability and low residual magnetic flux, and a magnet body made of a permanent magnet material. An electromagnetic flowmeter characterized by being configured by connecting in series.