JP2018189403A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic flowmeter having higher measurement accuracy than ever before.SOLUTION: In an electromagnetic flowmeter 10, a detection electrode 50 comprises a porous electrode 51 composed of a porous conductor and a solid electrode 55 conductively connected to the porous electrode 51. Water infiltrates into the porus electrode 51, which is a part of the detection electrode 50, thereby making it possible to secure a large contact area between the detection electrode 50 and water. While the porous electrode 51 is embedded into a flow channel housing 20, the solid electrode 55 is housed in an electrode housing hole 35 formed in the flow channel housing 20. A porous-side coupling part 53 of each porous electrode 51 and a solid-side coupling part 56 of each solid electrode 55 are fitted into each other in the electrode housing hole 35, and conductively connected.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an electromagnetic flow meter that measures the flow rate of water.

  In recent years, electromagnetic flow meters have been widely used in place of impeller flow meters (for example, Patent Document 1).

Japanese Patent Laid-Open No. 5-99715 (FIG. 1)

  However, in order to further spread the electromagnetic flow meter, improvement in measurement accuracy is required.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electromagnetic flowmeter with higher measurement accuracy than before.

  The invention of claim 1 made to achieve the above object comprises a resin flow channel housing having a measurement flow channel through which water flows in a state of receiving a magnetic field, and a porous conductor. A pair of porous electrodes embedded in a housing and facing each other in a direction crossing the magnetic field; and a pair of electrodes facing each other that are provided in the pair of porous electrodes and are exposed in the measurement channel and face each other A pair of electrode receiving holes communicating from the outer surface of the flow path housing to the pair of porous electrodes, a pair of solid electrodes received in the pair of electrode receiving holes, A porous-side connecting portion and a solid-side connecting portion which are formed on a real electrode and each of the porous electrodes and are connected to each other and are electrically connected; and the pair of solid electrodes and the pair of porous electrodes A pair of detections for detecting a potential difference between two points in the measurement channel It is an electromagnetic flowmeter provided with an electrode and the sealing member which seals the clearance gap between each said solid electrode and each said electrode accommodation hole.

  The invention according to claim 2 is the electromagnetic flow meter according to claim 1, further comprising an O-ring as the seal member sandwiched between an outer surface of the solid electrode and an inner surface of the electrode housing hole.

  According to a third aspect of the present invention, in each of the porous electrodes, a part or the whole of one side surface forms the electrode facing surface, and a part other than the other side surface other than the electrode facing surface constitutes the flow path housing. The electromagnetic flowmeter according to claim 1, comprising: a head portion covered with a resin to be covered; and a cylindrical or rod-like porous side connecting portion protruding from the part of the other side surface of the head portion. .

  According to a fourth aspect of the present invention, the porous side connecting portion has a cylindrical shape, and an end portion on the head portion side is covered with a resin constituting the flow path housing, and the solid electrode has a circular cross section. The electromagnetic flowmeter according to claim 3, wherein the electromagnetic flowmeter is formed in a rod shape and a tip end portion of the solid side connection portion is fitted into the porous side connection portion.

  The invention according to claim 5 is characterized in that the O-ring as the sealing member sandwiched between the outer surface of the intermediate portion in the axial direction of the solid electrode and the inner surface of the electrode receiving hole, and the O-ring It is an electromagnetic flowmeter of Claim 4 provided with the O-ring positioning part pinched and positioned between the said porous side connection parts in the axial direction of a real electrode.

  The invention according to claim 6 is the electromagnetic flowmeter according to any one of claims 1 to 5, wherein the pair of electrode facing surfaces are flush with an inner surface of the measurement flow path.

  The invention according to claim 7 is the electromagnetic flow rate according to claim 6, wherein the porous electrode has a shape constricted toward the electrode facing surface, and only the electrode facing surface is exposed to the measurement flow path. It is a total.

  According to an eighth aspect of the present invention, the cross-sectional shape of the portion where the pair of porous electrodes is located in the measurement channel is a quadrangle, and the pair of electrode facing surfaces are a quadrangle. The electromagnetic flow meter according to any one of claims 1 to 7.

  The invention according to claim 9 is the electromagnetic flowmeter according to any one of claims 1 to 8, wherein the porous electrode is made of graphite.

  A tenth aspect of the invention is the electromagnetic flowmeter according to the ninth aspect, wherein the graphite is hydrophilized.

  One of the factors affecting the measurement accuracy of the electromagnetic flow meter is an electrochemical double layer capacity that is a capacitance between the sensing electrode and water. If the contact area between the sensing electrode and water is small, the electrochemical double layer capacity is small and the impedance between the pair of sensing electrodes is large. Therefore, it is difficult for current due to electromagnetic induction to flow between the pair of sensing electrodes, and noise. It becomes easy to be affected. On the other hand, in the electromagnetic flowmeter of the present invention, a pair of detection electrodes is composed of a pair of porous electrodes made of a porous conductor, and a pair of solid electrodes that are conductively connected to the porous electrodes. It consists of electrodes. Then, water penetrates into the porous electrode which is a part of the detection electrode, and a large contact area between the detection electrode and water can be secured. Thereby, the electrochemical double layer capacity is increased, the influence of noise is suppressed, and the measurement accuracy of the flow rate is improved. The pair of porous electrodes are embedded in the flow path housing, while the pair of solid electrodes are accommodated in a pair of electrode accommodation holes formed in the flow path housing. And the porous side connection part of each porous electrode and the solid side connection part of each solid electrode are mutually connected in the electrode accommodation hole, and are conductively connected. With such a configuration, a pair of porous electrodes can be easily fixed to the channel housing by insert molding of the channel housing, and a pair of solid electrodes to the pair of electrode housing holes And the assembly of the porous electrode and the solid electrode can be easily performed. In addition, since the gap between the solid electrode and each electrode housing hole is sealed with a sealing member, even when water penetrates through the porous electrode, it is easy to prevent water from leaking out of the flow path housing. Can do.

  The seal member may be configured by solidifying a filling-type sealant, may be a packing, or may be an O-ring. The packing and the O-ring may be sandwiched in the fitting direction of the solid electrode with respect to the electrode housing hole. Further, when the O-ring is sandwiched between the outer surface of the solid electrode and the inner surface of the electrode housing hole as in the configuration of claim 2, the solid electrode is fitted into the electrode housing hole. Sealing can be performed by operation.

  As in the configuration of claim 3, the porous electrode has a structure in which a cylindrical or rod-like porous side connecting portion protrudes from a part of the side surface of the head portion, and the electrode facing surface of the head portion and the porous side connecting portion are By covering the portion other than the protruding portion with the resin constituting the flow path housing, the portion of the porous electrode exposed to the electrode housing hole side can be reduced, and the sealing process by the sealing member can be easily performed. .

  If the porous side connecting portion is formed in a cylindrical shape and the end portion on the head portion side is covered with the resin constituting the flow path housing as in the configuration of claim 4, the insert molding die is porous. The flow path housing can be easily formed by holding the tip of the side connecting portion.

  According to the structure of Claim 5, an O-ring is positioned by the porous side connection part, and a seal | sticker is stabilized.

  According to the configuration of the sixth aspect, since the pair of electrode facing surfaces are flush with the inner surface of the measurement channel, the turbulent flow in the measurement channel is suppressed and the measurement accuracy is improved.

  According to the configuration of the seventh aspect, since the porous electrode has a shape constricted toward the electrode facing surface, while maintaining the balance of the size of the electrode facing surface with respect to the measurement channel, The contact area with water can be increased.

  According to the configuration of the eighth aspect, since the electrode facing surface of the porous electrode is made square with respect to the measuring channel having a quadrangular cross-sectional shape, the electrode facing surface can be widened and the measurement accuracy can be increased.

  The porous electrode may be one obtained by drilling a plurality of holes in a metal, or may be sintered metal or graphite (the invention of claim 9). In addition, when a porous electrode is comprised with a graphite, it is preferable to perform a hydrophilization process (invention of Claim 10).

The perspective view of the electromagnetic flowmeter which concerns on 1st Embodiment of this invention. Back cross section of meter body Perspective view of flow path housing Front sectional view around the measurement part of the flow path housing Plan sectional view of the sensing electrode and its peripheral parts Plan sectional view of the sensing electrode and its peripheral parts according to the second embodiment

[First Embodiment]
Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. The electromagnetic flow meter 10 of the present embodiment shown in FIG. 1 is used as, for example, a water meter, and is a meter in which a plurality of parts are assembled in an intermediate portion of a resin flow channel housing 20 extending in the horizontal direction. It has a main body 10 </ b> H, and the meter main body 10 </ b> H is housed in a rectangular parallelepiped case 13. And the flow path housing 20 is connected to the middle of a water pipe, and tap water flows in the measurement flow path 20R which penetrates the flow path housing 20 in a longitudinal direction from one end to the other end. In addition, the direction through which tap water flows is shown by the arrow A in FIG.1, FIG3 and FIG.4.

  As shown in FIG. 4, the measurement flow path 20 </ b> R has the measurement unit 20 </ b> K most narrowed at a position that is gradually narrowed from both ends toward the center and slightly shifted to the downstream side from the center. As shown in FIG. 2, the measuring unit 20K has a horizontally-long rectangular cross-section with four corners, and extends over a predetermined length as shown in FIG. Further, both end portions of the measurement flow path 20R have a circular cross section, and the cross-sectional shape gradually changes from a circular shape to a rectangular shape from both end portions toward the measurement portion 20K.

  As shown in FIG. 3, an orthogonal sleeve 25 that is orthogonal to the axial direction of the flow path housing 20 is provided at the center of the flow path housing 20 in the longitudinal direction. As shown in FIG. 4, the measurement unit 20K described above is located in the orthogonal sleeve 25, and a pair of electrode support projections projecting laterally from both side surfaces of the flow path housing 20 on both sides of the measurement unit 20K. Portions 31, 31 and a pair of fixed protrusions 32, 32 are provided. The electrode support protrusion 31 and the fixed protrusion 32 are adjacent to each other and integrated as shown in FIG.

  Further, as shown in FIG. 2, component housing spaces 30 and 30 are formed in the flow path housing 20 above and below the measurement unit 20K. Further, as shown in FIG. 4, the coil 26 is accommodated in a state where the winding axis thereof is directed in the vertical direction on the side opposite to the fixed protrusion 32 of the one electrode support protrusion 31. Yes. Then, a pair of yokes 27 (only one yoke 27 is shown in FIG. 4) joined to both ends of an iron core (not shown) of the coil 26 extend to the component housing spaces 30, 30. The flat end portions 27A and 27A of the 27 and 27 are disposed so as to face each other with the measurement portion 20K of the measurement flow path 20R interposed therebetween as shown in FIG.

  Now, as shown in FIG. 4, a pair of porous electrodes 51 and 51 are embedded on both sides of the measurement unit 20K in the flow path housing 20 on the extension lines of the electrode support protrusions 31 and 31 described above. A pair of electrode receiving holes 35, 35 extending from the front end surface of each electrode support protrusion 31 to the porous electrode 51 are formed.

  The porous electrode 51 is made of a hydrophilic conductor (for example, graphite) that has been subjected to a hydrophilic treatment, and includes a head portion 52 and a porous-side connecting portion 53 as shown in FIG. The head portion 52 has a rectangular parallelepiped shape, and one side surface thereof is an electrode facing surface 51A arranged flush with the inner surface of the measurement channel 20R. Although not illustrated, when the electrode facing surface 51A is viewed from the facing direction of the porous electrodes 51, 51, a rectangular shape that is long in the axial direction of the measurement flow path 20R is formed, and is positioned at the center in the vertical direction of the measurement unit 20K.

  The porous side connecting portion 53 has a cylindrical shape, for example, and protrudes from the center of the side surface of the head portion 52 opposite to the electrode facing surface 51A. In addition, an outer surface proximal end portion of the porous side connecting portion 53 is provided with a curved surface 53R having an R chamfer.

  The electrode housing hole 35 has a concentric cross section larger than the outer diameter of the porous side connecting portion 53. The distal end side of the porous side connecting portion 53 from the middle position in the axial direction protrudes from the center of the back surface of the electrode housing hole 35. This structure can be easily formed by holding the tip end portion of the porous side connecting portion 53 in a molding die (not shown) for insert-molding the flow path housing 20.

  A solid electrode 55 is accommodated in each electrode accommodation hole 35. The solid electrode 55 is made of, for example, stainless steel, and has a rod shape as a whole. Further, the solid electrode 55 is formed with an intermediate large-diameter portion 57 by expanding the intermediate portion in a stepped shape, and the tip side of the intermediate large-diameter portion 57 forms a solid-side connecting portion 56, but the opposite. The side is a wire connection part 58. Moreover, the front-end | tip part of the solid side connection part 56 has comprised the taper shape. And the solid side connection part 56 is fitted by the fitting hole 53A in the above-mentioned porous side connection part 53, and the solid electrode 55 and the porous electrode 51 are conductively connected. Further, the detection electrode 50 is constituted by the conductively connected porous electrode 51 and the solid electrode 55, and as shown in FIG. 4, a pair of detection electrodes 50, 50 are arranged on both sides of the measurement flow path 20R. ing.

  The solid side connecting portion 56 shown in FIG. 5 is slightly shorter than the porous side connecting portion 53, and the front end surface of the intermediate large diameter portion 57 abuts on the front end surface 53 T of the porous side connecting portion 53. ing. An O-ring 36 as a seal member is sandwiched between the intermediate large diameter portion 57 and the inner surface of the electrode housing hole 35.

  The O-ring 36 and the solid electrode 55 are prevented from coming off by the electrode fixing member 40. The electrode fixing member 40 is superimposed on the tip surfaces of the electrode support protrusion 31 and the fixed protrusion 32, and is fitted with the fitting protrusion 41 fitted into the electrode housing hole 35, and the mounting hole 32 </ b> A formed in the fixed protrusion 32. And a screw insertion hole 42 that overlaps with the screw insertion hole 42. Then, a screw (not shown) passed through the screw insertion hole 42 is screwed into the mounting hole 32 </ b> A, and the electrode fixing member 40 is fixed to the flow path housing 20. Moreover, the electrode insertion hole 43 penetrates the center part of the fitting protrusion 41, and the tip side of the fitting protrusion 41 is expanded in a stepped shape from the middle part of the electrode insertion hole 43. Then, the solid electrode 55 is inserted into the electrode insertion hole 43, and the base end surface of the intermediate large diameter portion 57 abuts on the step surface 43 </ b> D of the electrode insertion hole 43, thereby causing the solid electrode 55 to enter the electrode accommodation hole 35. It has been retained. Further, the O-ring 36 abuts against the tip end surface 41T of the fitting protrusion 41 and is prevented from coming off into the electrode receiving hole 35, and at the back of the electrode receiving hole 35 by the tip end surface 53T of the porous side connecting portion 53. The movement to is regulated. The front end surface 41T of the fitting protrusion 41 corresponds to an O-ring positioning portion.

  Further, the wire connecting portion 58 of the solid electrode 55 extends through the electrode fixing member 40 to the outside of the electrode housing hole 35. As shown in FIG. 2, an electric wire 90 is connected to the distal end portion of the electric wire connecting portion 58, extends above the flow path housing 20, and is connected to the control board 60 in the control unit 10U. Further, an electric wire (not shown) of the coil 26 is connected to the control board 60 in the same manner.

  This completes the description of the configuration of the electromagnetic flow meter 10 of the present embodiment. Next, the effect of the electromagnetic flow meter 10 will be described. The electromagnetic flow meter 10 is connected to the middle of the water pipe and operates to measure the flow rate of water flowing through the water pipe. For this purpose, the control board 60 applies an alternating current to the coil 26 and applies an alternating magnetic field to the measurement unit 20K of the measurement flow path 20R from the side. When water flows through the measurement unit 20K in this state, a potential difference corresponding to the flow rate of water is generated between the electrode facing surfaces 51A and 51A of the pair of detection electrodes 50 and 50 by electromagnetic induction. The control board 60 calculates the flow rate of water per unit time based on the potential difference and the cross-sectional area of the measuring unit 20K, and calculates the integrated flow rate by integrating the flow rate. The calculation results are displayed on the monitor 61 above the control board 60.

  By the way, as one of the elements that affect the measurement accuracy of the electromagnetic flow meter 10, there is an electrochemical double layer capacity that is a capacitance between the detection electrode 50 and water. Specifically, when the contact area between the detection electrode 50 and water is small, the electrochemical double layer capacity is reduced and the impedance between the pair of detection electrodes 50, 50 is increased, and thus the pair of detection electrodes 50, 50. In the meantime, the current due to electromagnetic induction becomes difficult to flow, and is easily affected by noise. On the other hand, in the electromagnetic flow meter 10 of the present embodiment, as described above, the pair of detection electrodes 50 and 50 are a pair of porous electrodes 51 and 51 formed of a porous conductor, and these porous electrodes are porous. It consists of a pair of solid electrodes 55, 55 that are conductively connected to the quality electrodes 51, 51. Then, water penetrates into the porous electrode 51 which is a part of the detection electrode 50, and a large contact area between the detection electrode 50 and water can be secured. Thereby, the electrochemical double layer capacity is increased, the influence of noise is suppressed, and the measurement accuracy of the flow rate is improved.

  The pair of porous electrodes 51, 51 are embedded in the flow path housing 20, while the pair of solid electrodes 55, 55 are paired with a pair of electrode receiving holes 35, formed in the flow path housing 20. 35. In addition, the porous-side connecting portion 53 of each porous electrode 51 and the solid-side connecting portion 56 of each solid electrode 55 are fitted and connected to each other in the electrode housing hole 35.

  With such a configuration, the pair of porous electrodes 51, 51 can be easily fixed to the flow path housing 20 by insert molding of the flow path housing 20, and the pair of electrode housing holes 35, 35 The pair of solid electrodes 55 and 55 can be easily assembled to each other, and the porous electrodes 51 and 51 and the solid electrodes 55 and 55 can be easily assembled.

  Further, the porous electrode 51 has a structure in which the cylindrical porous side connecting portion 53 protrudes from the head portion 52, and the head portion 52 other than the portion where the electrode facing surface 51A and the porous side connecting portion 53 protrude is provided. Since it is covered with the resin constituting the flow path housing 20, the portion of the porous electrode 51 exposed to the electrode housing hole 35 side can be reduced, and the water that permeates the porous electrode 51 can be removed from the solid electrode. It can be easily dammed by the O-ring 36 between the electrode 55 and each electrode receiving hole 35.

  In addition, since the electrode facing surface 51A of the porous electrode 51 is flush with the inner surface of the measurement flow path 20R, turbulent flow in the measurement flow path 20R can be suppressed, and the measurement accuracy is improved in this respect as well. Furthermore, since the electrode facing surface 51A of the porous electrode 51 is rectangular with respect to the measurement channel 20R having a square cross-sectional shape, the electrode facing surface 51A can be widened, and also in this respect, the measurement accuracy is improved. To do.

[Second Embodiment]
This embodiment is shown in FIG. 6, and the structure of the detection electrode 50V is different from that of the first embodiment. The porous electrode 51V constituting a part of the detection electrode 50V of the present embodiment has, for example, a structure in which a frustoconical protrusion 82 protrudes from one side surface of a rectangular parallelepiped body 81. The tip surface of the frustoconical protrusion 82 is the electrode facing surface 51A and is arranged flush with the inner surface of the measurement channel 20R. A circular recess 84 is formed in the center of the main body 81 on the opposite side of the truncated cone-shaped protrusion 82, and a porous side connecting portion 83 that is a circular hole is formed in the center of the bottom of the circular recess 84. ing. Further, the electrode housing hole 35V has a small diameter portion 35A having one end side continuous to the circular recess 84, and the other end side is enlarged in a stepped shape to form a large diameter portion 35B. This structure can be easily formed by fitting the tip of the support protrusion of a molding die (not shown) for insert-molding the flow path housing 20V into the circular recess 84 of the porous electrode 51V.

  Further, the solid electrode 55V has a circular cross section, and includes a solid side connecting portion 70, an intermediate small diameter portion 71, an intermediate large diameter portion 72, a flange portion 73, and a connection protrusion 74 in order from the distal end side. Then, in a state where the O-ring 36 is fitted to the base end portion of the solid side connecting portion 70, the solid side connecting portion 70 is inserted into the electrode housing hole 35 </ b> V from the solid side connecting portion 70 side. And the front end side of the solid side connection part 70 is fitted to the porous side connection part 83 of the porous electrode 51V, and the intermediate small diameter part 71 of the solid electrode 55V is fitted to the small diameter part 35A of the electrode housing hole 35V. And the intermediate | middle large diameter part 72 of the solid electrode 55V is fitted by the large diameter part 35B of the electrode accommodation hole 35V. Further, a screw passed through a through hole (not shown) of the flange portion 73 is tightened into a mounting hole (not shown) of the flow path housing 20V, and the solid electrode 55V is fixed to the flow path housing 20V. Furthermore, an electric wire (not shown) is soldered or brazed to the connection protrusion 74.

  According to the electromagnetic flow meter 10V of this embodiment, in addition to the effects of the electromagnetic flow meter 10 of the first embodiment, the porous electrode 51V has a shape constricted toward the electrode facing surface 51A. While maintaining the balance of the size of the electrode facing surface 51A with respect to the measurement flow path 20R, the volume of the entire porous electrode 51V embedded in the flow path housing 20V is increased to increase the contact area between the porous electrode 51V and water. Can be bigger.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) The porous electrode 51 of the first embodiment is graphite, but it may be a metal having a plurality of holes drilled or a sintered metal.

  (2) Although the electromagnetic flow meter 10 of the first embodiment includes the O-ring 36 as a seal member, the seal member may be constituted by a filling-type sealant, and packing is used as the seal member. May be used.

  (3) In the first embodiment, the porous electrode 50 may be cylindrical or polygonal. Further, the tip of the porous electrode 50 may protrude inside the measurement channel 20.

10,10V Electromagnetic flow meter 20,20V Channel housing 35,35V Electrode receiving hole 36 0 ring (seal member)
50, 50V detection electrode 51 porous electrode 51A electrode facing surface 52 head portion 53, 83 porous side connection portion 55, 55V solid electrode 55V solid electrode 56, 70 solid side connection portion

Claims (10)

A resin-made channel housing having a measurement channel through which water flows under a magnetic field;
A pair of porous electrodes that are made of a porous conductor and are embedded in the flow path housing and face each other in a direction crossing the magnetic field;
A pair of electrode facing surfaces that are provided on the pair of porous electrodes and are exposed in the measurement channel and face each other;
A pair of electrode receiving holes communicating from the outer surface of the flow path housing to the pair of porous electrodes;
A pair of solid electrodes housed in the pair of electrode housing holes;
A porous-side coupling portion and a solid-side coupling portion that are formed on each solid electrode and each of the porous electrodes, are fitted to each other, and are conductively connected;
A pair of detection electrodes configured by the pair of solid electrodes and the pair of porous electrodes to detect a potential difference between two points in the measurement channel;
An electromagnetic flowmeter comprising: each solid electrode and a seal member that seals a gap between each electrode accommodation hole.   The electromagnetic flow meter according to claim 1, further comprising an O-ring as the seal member sandwiched between an outer surface of the solid electrode and an inner surface of the electrode housing hole.   Each of the porous electrodes is a head in which a part or the whole of one side surface forms the electrode facing surface, and a part other than the other side surface other than the electrode facing surface is covered with a resin constituting the flow path housing. The electromagnetic flow meter according to claim 1, comprising: a portion and a cylindrical or rod-shaped porous side connecting portion protruding from the part of the other side surface of the head portion. The porous side connecting portion has a cylindrical shape, and an end portion on the head portion side is covered with a resin constituting the flow path housing,
The electromagnetic flowmeter according to claim 3, wherein the solid electrode has a bar shape with a circular cross section, and a front end portion of the solid electrode forms the solid side connection portion fitted into the porous side connection portion. An O-ring as the seal member sandwiched between the outer side surface of the intermediate portion in the axial direction of the solid electrode and the inner side surface of the electrode housing hole;
The electromagnetic flowmeter according to claim 4, further comprising an O-ring positioning unit that positions the O-ring between the porous-side connecting portion in the axial direction of the solid electrode.   The electromagnetic flow meter according to any one of claims 1 to 5, wherein the pair of electrode facing surfaces are flush with an inner surface of the measurement channel.   The electromagnetic flowmeter according to claim 6, wherein the porous electrode has a shape constricted toward the electrode facing surface, and only the electrode facing surface is exposed to the measurement channel.   8. The cross-sectional shape of a portion where the pair of porous electrodes is located in the measurement channel is a quadrangle, and the pair of electrode facing surfaces is a quadrangle. The electromagnetic flowmeter according to claim.   The electromagnetic flow meter according to claim 1, wherein the porous electrode is made of graphite.   The electromagnetic flowmeter according to claim 9, wherein the graphite is subjected to a hydrophilic treatment.

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