JPS6242012A - Electrode for electromagnetic flow meter - Google Patents

Abstract

PURPOSE:To increase an electrode diameter with a small quantity of using metal and to prevent the performance reduction at the time of using a flow meter by providing in extending the connecting part at one edge of a cap formed by a high melting point conductive metallic cover at the outer circumferential surface of the spindle for the electrode and the fluid side surface to be measured. CONSTITUTION:An electrode 3 consists of a cap 6 to cover and form a spindle 5 for the cylindrical electrode formed by the burned ceramic, an outer circumferential surface 5a of the spindle 5 and a measured fluid side surface 5b with the high melting point conductive metal, and a connecting part 7 is extended at one edge of the cap 6. Thus, even when the metal used is small in quantity, the electrode diameter can be enlarged, and the adverse effect to the performance can be eliminated at the time of using the electromagnetic flow meter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrode for an electromagnetic flowmeter suitable for use in an electromagnetic flowmeter equipped with a ceramic tube.

[Conventional technology]

Conventionally, electrodes for this type of electromagnetic flowmeter have been made of metal or conductive ceramic.

[Problems to be Solved by the Invention] However, the former, that is, the metal electrode, must satisfy the conditions that it has durability against the firing temperature of ceramic and that its coefficient of thermal expansion is close to that of ceramic. However, there is a problem in that usable metals are limited to expensive metals such as platinum.

Therefore, it is possible to reduce the outer diameter of the electrode, but
In this case, when viewed from the side of the converter for the electromagnetic flowmeter, the input impedance becomes high, which is disadvantageous in that it adversely affects its performance.

On the other hand, the latter electrode, that is, a conductive ceramic electrode, has a performance problem similar to the case described above because its conductivity is inferior to that of ordinary metal, although it varies somewhat depending on the composition.

[Means for solving problems]

The electromagnetic flowmeter electrode according to the present invention is a bottomed cylindrical electrode formed by coating two ceramic electrode rods and the outer circumferential surface of the core rod and the side surface of the fluid to be measured with a high melting point conductive metal. A connecting portion for connecting a lead wire is provided at one end of the cap.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electrode for an electromagnetic flowmeter that can reduce costs and does not adversely affect the performance of the meter when it is used.

[For production]

The present invention consists of a ceramic electrode core rod and a bottomed cylindrical cap formed by coating the outer peripheral surface of the core rod and the side surface of the fluid to be measured with a high melting point conductive metal. Even if less metal is used, the electrode diameter can be increased.

〔Example〕

1 and 2 are a sectional view and a perspective view showing an electrode for an electromagnetic flowmeter according to the present invention. In the figure, the reference numeral 1 indicates a measurement tube for an electromagnetic flowmeter, in which a tube member 2 through which a fluid to be measured flows and a pair of electrodes 3 (one of which detects the electromotive force generated at each point of the fluid to be measured). (only shown),
It is held under pressure by two connecting pipes (not shown). The tube member 2 is made of unfired or semi-fired ceramic, and has two electrode mounting holes 4 (only one shown) opening in and out of the tube in the center in the axial direction. The electrode 3 includes a cylindrical electrode core 5 made of fired ceramic, and an outer peripheral surface 5a of the electrode core 5 and a side surface 5b of the fluid to be measured made of a high melting point conductive metal with a thickness of about 0.5 m. and a bottomed cylindrical cap 6 formed by covering the electrode with a cap 6, and are attached to the electrode attachment hole 4 so as to face each other. A cylindrical connecting portion 7 that is exposed to the outside extends from one end of the cap 6 of the electrode 3 . Two small holes 8 are bored in this connecting portion 7, and a signal lead wire 9 is inserted through both of these small holes 8, and the tip end thereof is soldered. Here, as the high-melting point conductive metal, a metal such as platinum or a platinum-iridium alloy, which has a melting point higher than the ceramic firing temperature at the time of manufacturing the measuring tube, is used.

In the electromagnetic flowmeter electrode configured in this way, a ceramic electrode core 5 and an outer circumferential surface 5a of this core 5 are used.
and a bottomed cylindrical cap 6 formed by coating the side surface 5b of the fluid to be measured with a high melting point conductive metal, so the electrode diameter can be increased even if less metal is used.

Next, a method of manufacturing the measuring tube 1 having the above-described configuration will be explained.

First, the electrode 3 is formed by coating the electrode core rod 5 made of fired ceramic with a high melting point conductive metal. Next, the tube member 2 and the electrode 3 are integrated by fitting this electrode 3 into an electrode attachment hole 4 formed in the tube member 2 made of unfired or semi-fired ceramic. Thereafter, this is fired at a firing temperature of 1300 to 1400°C.

Measuring tube 1 for an electromagnetic flowmeter equipped with electrodes 3 in this way
can be manufactured reliably.

According to such a measuring tube manufacturing method, since the electrode 3 having the electrode core 5 made of ceramic and the tube member 2 made of unfired or semi-fired ceramic are integrated and fired, the electrode 3 is attached to the tube member 2. The thermal expansion coefficient of the electrode 3 and the thermal expansion coefficient of the tube member 2 can be fixed reliably against the electrode 3 and that of the tube member 2. Since they are approximately the same, the sealing performance will not deteriorate even if there is a temperature change.

In manufacturing the measuring tube 1 according to this embodiment, an example is shown in which a fired ceramic material is used for the electrode core 5, but in the present invention, a material with a relatively small shrinkage margin is selected as the electrode core 5. A semi-fired ceramic material may also be used. That is, in short, when the tube member 2 and the electrode core rod 5 are formed of the same composition material, the electrode core rod 5 whose semi-baking temperature is higher than that of the tube member 2 is combined. Just use it.

In addition, in the method for manufacturing the measuring tube 1 in this embodiment, a small hole 8 is bored in the connecting portion 7 when forming the electrode 3, but this hole machining may be performed before or after firing the measuring tube 1. is possible.

Furthermore, in this embodiment, the case where the connecting portion 7 is cylindrical is shown, but the present invention is not limited to this.
Alternatively, the connecting portion 10 may have a rectangular shape as shown in FIGS. 30 and 4, and in this case, a mounting hole I2 for connecting the signal lead wire 11 is provided approximately in the center of the connecting portion 10.
is drilled.

Furthermore, the shape of the electrode core rod 5 in the present invention is not limited to the above-described embodiments, and may be, for example, tapered, and the shape can be modified as appropriate.

〔Effect of the invention〕

As explained above, according to the present invention, a bottomed cylindrical member is formed by coating a ceramic electrode core rod, the outer circumferential surface of the two rods, and the side surface of the fluid to be measured with a high melting point conductive metal. Since the connecting portion for connecting the lead wire is extended from one end of the cap, the electrode diameter can be increased even if less metal is used. Therefore, the cost can be reduced, and the performance of the electromagnetic flowmeter is not adversely affected when used, unlike conventional electromagnetic flowmeters.

[Brief explanation of drawings]

1 and 2 are a sectional view and a perspective view showing an electrode for an electromagnetic flowmeter according to the present invention, and FIGS. 3 and 4 are a sectional view and a perspective view showing another embodiment. 3...electrode, 5...electrode core rod, 5a...
Outer circumferential surface, 5b... Side surface of the fluid to be measured, 6... Cap, 7... Connection section, 9... - Signal lead wire.

Claims (1)

[Claims] It consists of a ceramic electrode core and a bottomed cylindrical cap formed by coating the outer circumferential surface of the core and the side surface of the fluid to be measured with a high melting point conductive metal.A lead is attached to one end of the cap. An electrode for an electromagnetic flowmeter characterized by an extended connection part for connecting a line.