JPS59198319A - Electromagnetic flow meter - Google Patents

Abstract

PURPOSE:To effect cost-down by reducing exciting current and number of turns of coils, by arranging permanent magnets or exciting coils emitting vertically to the magnetic field of exciting coils magnetic fluxes oriented to the inside of pipe respectively in the neighborhood of a pair of electrodes located on the pipe wall. CONSTITUTION:Permanent magnets 11 emitting magnetic fluxes 12 vertically to magnetic field 3 of exciting coils 4 towards inside of a measuring pipe 2 are installed in the neighborhood of a pair of electrodes 6 on the outer side of the measuring pipe 2. As the magnetic fluxes of exciting coils 4 pass on the inside instead of outside of the measuring pipe 2 rejecting magnetic fluxes 12 emitted from the permanent magnets 11, the magnetic density inside the pipe is increased by the magnetic coils 4. Consequently, reduction of exciting current and number of turns of coil enables reduction of costs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electromagnetic flowmeter that electrically measures the flow rate of a fluid flowing within a measuring tube.

[Prior art]

In general, an electromagnetic flowmeter converts the flow rate of a conductive fluid flowing in a measuring tube into an electrical signal using Faraday's electromagnetic induction phenomenon to measure the flow rate.
It is configured as shown in the figure. That is, a measuring tube 2 lined with an insulating lining 1 is connected with seven flange joints between the pipes through which the fluid to be measured flows, and on the outside of the measuring tube 2 there are holes perpendicular to the flow direction of the fluid to be measured inside the tube. A pair of excitation coils 4 forming a magnetic field 3 are connected to a core 5 and a mounting base (not shown).
are installed facing each other. Further, a tube wall 2aKki of the measurement tube 2, and a pair of electrodes 6 are provided so as to face each other via a magnetic field 3 at right angles to the flow direction of the fluid to be measured in the measurement tube 2.

However, in conventional electromagnetic flowmeters, as the diameter of the measuring tube increases, the leakage rate of magnetic flux increases, as shown in Figure 2, so in order to obtain the desired magnetic flux, it is necessary to increase the excitation current. Alternatively, the number of turns of the excitation coil (40) must be increased, which is disadvantageous in that the cost increases.

[Summary of the invention]

The present invention was developed in view of the above circumstances, and has an extremely simple structure in which permanent magnets or excitation coils are disposed near both electrodes, respectively, to emit magnetic flux toward the inside of the tube at right angles to the magnetic field direction of the excitation coil. Furthermore, the present invention provides an electromagnetic flowmeter that focuses magnetic flux into a pipe and reduces costs by reducing the excitation current and the number of turns of the coil. Hereinafter, the configuration and the like will be explained in detail with reference to embodiments shown in the drawings.

〔Example〕

FIG. 3 shows an embodiment of an electromagnetic flowmeter according to the present invention. In the following figures, the same members as in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed explanations will be omitted.

Permanent magnets designated by reference numeral 11 emit a magnetic flux 12 toward the inside of the tube at right angles to the direction of the magnetic field 3 of the excitation coil 4, and are arranged near the electrodes 6 on the outside of the measurement tube 2, respectively. As a result, the magnetic field 3 created by the excitation coil 4
In other words, the magnetic flux 3a is focused inside the tube to increase the magnetic flux density inside the tube.

Therefore, when the excitation coil 4 is excited, a magnetic field having a magnetic flux 3a crossing the fluid to be measured flowing in the measuring tube 2 and perpendicular to the flow direction thereof is formed. Then, an electromotive force proportional to the average flow velocity is generated in the electrode 6, and after this is guided to the amplifier via a lead wire and a terminal board (not shown), a signal is issued, thereby controlling the amount of current at which the flow rate is measured. is sometimes carried out.

In the electromagnetic flowmeter configured in this way, the excitation coil 4 repels the magnetic flux 12 emitted by the permanent magnet 11 and passes through the inside of the measuring tube 2 without passing through the outside. The magnetic flux density increases, and the magnetic flux 3a of the exciting coil 4 can be used effectively.

In this embodiment, the excitation method is based on a direct current magnetic field, but the present invention is not limited to this. However, as shown in FIG. 4, an alternative magnetic field may be used. do not have. However, in this case, instead of the permanent magnet 11, a magnetic flux 1 is placed near the electrode 6 at right angles to the magnetic field direction of the exciting coil 4.
The same effect as in the embodiment can be obtained by disposing an excitation coil 14 that outputs a current of play.

〔Effect of the invention〕

As explained above, according to the present invention, permanent magnets or excitation coils that emit magnetic flux toward the inside of the tube at right angles to the magnetic field direction of the excitation coil are arranged near both electrodes, so that the magnetic flux density inside the tube is reduced during use. This makes it possible to use magnetic flux extremely effectively. Therefore, in order to obtain the same electromotive force, the number of turns of the excitation coil can be reduced and the excitation current can be made weaker compared to the prior art, and manufacturing costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing a conventional electromagnetic flowmeter, Fig. 2 is a cross-sectional view for explaining the state of magnetic flux, and Fig. 3 is a cross-sectional view for explaining the state of magnetic flux in the electromagnetic flowmeter according to the present invention. 4 are sectional views showing other embodiments. 2... Measuring tube, 2366... Tube wall, 3... Magnetic field, 4... Excitation coil, 6... Electrode, 11-...
・Permanent magnet, 14... Excitation coil. −

Claims (1)

[Claims] A pair of excitation coils are provided outside the measurement tube and form a magnetic field perpendicular to the flow direction of the fluid to be measured in the tube, and a pair of electrodes are provided on the tube wall so as to face each other across the magnetic field. An electromagnetic flowmeter characterized in that a permanent magnet or an excitation coil is disposed near both of the electrodes, each of which emits a magnetic flux toward the inside of the tube at right angles to the direction of the magnetic field of the excitation coil.