JPH07253346A - Electromagnetic flow meter - Google Patents

Abstract

PURPOSE:To save power and reduce cost by eliminating the need for an excitation circuit. CONSTITUTION:In the title meter for measuring the flow rate of a fluid 1 to be measured by applying magnetic field to the fluid 1 to be measured with a conductivity for flowing in a measurement pipe 2 so that the magnetic field crosses the flow direction and by taking out electromagnetic force induced in the fluid 1 to be measured with a pair of electrodes for detecting the electromagnetic force, at least a pair of liquid-junction type electrodes 21 and 22 with a conductive internal liquid are used as electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a magnetic field to a fluid to be measured having conductivity which flows in a measuring tube so as to be orthogonal to the flow direction of the fluid to generate a pair of electromotive forces induced in the fluid to be measured. The present invention relates to an electromagnetic flow meter that measures the flow rate of a fluid to be measured by taking it out and detecting it with an electrode, and particularly to an electromagnetic flow meter that does not require an excitation circuit to achieve power saving and cost reduction.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic flow meter has been widely used as one of the measuring instruments for measuring the flow rate of a fluid to be measured. In this electromagnetic flowmeter, when a magnetic field is applied so as to be orthogonal to the flow direction of the fluid to be measured that has conductivity inside the measuring tube, the magnitude of the electromotive force induced in the fluid to be measured is the flow velocity of the fluid to be measured. The Faraday's law of electromagnetic induction, which is proportional to, is used to measure the flow rate of the fluid to be measured.

In this case, the induction direction of the electromotive force follows the "Fleming's right-hand rule". Then, the induced electromotive force E is expressed by equation (1). E = K ・ B ・ D ・ V (1) where K: constant, B: magnetic flux density, D: inner diameter of tube, V:
Average flow velocity.

Therefore, if the induced electromotive force E can be measured, the average flow velocity V of the fluid to be measured can be obtained, and the flow rate Q of the fluid to be measured flowing in the measuring pipe can be obtained by the equation (2). Q = (π / 4) D ² V (2) FIG. 5 is a schematic diagram showing an example of the principle configuration of the detector of the conventional electromagnetic flowmeter of this type, and FIG. 6 is an electrical diagram of the electromagnetic flowmeter including the converter. It is a circuit diagram which shows an example of a physical system configuration.

In FIG. 5, a measuring tube 2 through which a fluid to be measured 1 is passed is provided with a lining 3 of an insulating material on its inner wall.
A pair of metal electrodes 4 and 5 for extracting the induced electromotive force
Airtightly attached at opposite positions on the tube wall on lines perpendicular to the flow and magnetic fields respectively. Further, the magnetic field generator is arranged so as to surround the measuring tube 2, and the exciting coil 6,
7 and cores 8 and 9.

Next, in the electromagnetic flow rate of such a configuration,
In the excitation circuit 11 in the converter 10, an alternating excitation current (sine wave or square wave) is passed through the excitation coils 6 and 7 to generate an alternating magnetic field. The electromotive force E induced in the fluid to be measured 1 is taken out by the pair of metal electrodes 4 and 5, signal-amplified by the amplifier 12 in the converter 10, and further signal-converted by the output circuit 13 to finally obtain the flow rate signal. Is output as.

By the way, in such an electromagnetic flow meter, since the metal electrodes 4 and 5 are used as the electrodes for taking out the induced electromotive force, when a DC magnetic field is used, the interface between the metal and the fluid to be measured 1 is used. Since a polarization phenomenon occurs at the contact point, the contact potential between the fluid to be measured 1 and the metal electrodes 4 and 5 fluctuates, and electrical noise is generated. As described above, an AC magnetic field that is not affected by the polarization phenomenon is used. ing.

Therefore, an alternating current excitation circuit is required, and power for excitation is also required, and there is a limit to the power saving of the instrument. On the other hand, in order to reduce the power consumption of the instrument, a DC magnetic field method using a permanent magnet that does not require electric power for excitation is ideal, but it should be realized by the conventional electromagnetic flowmeter using metal electrodes 4 and 5. It is difficult.

[0009]

As described above, in the conventional electromagnetic flowmeter, since the AC exciting circuit is required, not only is there a limit to the power saving of the meter, but also the cost is high. There was a problem. It is an object of the present invention to provide an electromagnetic flow meter that does not require an excitation circuit and can save power and reduce cost.

[0010]

In order to achieve the above object, first, in the invention according to claim 1, the fluid to be measured having conductivity which flows in the measuring pipe is orthogonal to the flow direction thereof. An electromagnetic flowmeter for measuring the flow rate of a fluid to be measured by applying a magnetic field and taking out and detecting electromotive force induced in the fluid to be measured with a pair of electrodes, wherein the electrode has an internal liquid having conductivity. It is composed of at least a pair of liquid junction electrodes.

According to a second aspect of the invention, in the electromagnetic flowmeter of the first aspect of the invention, the pressure of the fluid to be measured and the internal fluid of the fluid to be measured are provided between the fluid to be measured and the internal fluid of the liquid junction electrode. It is equipped with a pressure receiving part that balances the pressure.

Here, particularly as the liquid junction type electrode, a conductive internal liquid is pressurized under atmospheric pressure or more into an electrode container made of an insulating material, and a porous material is provided at the tip of the electrode container. The liquid junction type electrode body, which is equipped with a ceramic liquid junction and is airtightly attached to the electrode container by immersing the metal electrode in the internal liquid, is measured with a sealant to maintain airtightness. The pipe is attached so that the liquid junction is in contact with the fluid to be measured. As the magnetic field, a DC magnetic field is applied by using a pair of permanent magnets arranged so as to sandwich the measuring tube.

[0013]

Therefore, in the electromagnetic flowmeter of the present invention, at least a pair of liquid-junction electrodes having a conductive internal liquid are used as electrodes for extracting the induced electromotive force, and the metal electrode itself is used as the fluid to be measured. The metal electrode is always in contact with the internal liquid under a certain condition by making the conductive internal liquid come into contact with the fluid to be measured through the liquid junction without contacting it directly and the metal electrode is always in contact with the internal liquid. Since it has electrical continuity with the fluid to be measured through this internal liquid, and the contact potential does not change depending on the type and state of the fluid to be measured, a direct-current magnetic field method, that is, a permanent magnet is used. It becomes possible to realize a power type electromagnetic flow meter.

As a result, it is possible to save power and reduce costs by eliminating the need for an exciting circuit. Further, in the electromagnetic flowmeter of the invention according to claim 2, by providing a pressure receiving portion for balancing the pressure of the fluid to be measured and the pressure of the internal fluid between the fluid to be measured and the internal liquid of the liquid junction electrode. When the pressure of the fluid to be measured is high, it is possible to prevent the internal liquid from flowing out of the liquid junction and to prevent the fluid to be measured from entering.

[0015]

First, the concept of the present invention will be described. Unlike a reference electrode used for pH measurement by the glass electrode method, a conductive internal liquid such as a KCl (potassium chloride) solution does not directly contact the fluid to be measured with the metal electrode itself. Contact the fluid to be measured through the contact part, and
The electrode made of metal such as Cl (silver chloride) is always in contact with the conductive internal liquid such as KCl. By doing so, the metal electrode is always in contact with the internal liquid under a certain condition, has electrical continuity with the fluid to be measured through this liquid, and the contact potential is different depending on the type and state of the fluid to be measured. Since it does not change, it is possible to realize a DC magnetic field type, that is, a power saving type electromagnetic flow meter using a permanent magnet.

An embodiment of the present invention based on the above concept will be described below in detail with reference to the drawings.
FIG. 1 is a schematic view showing a configuration example of a detector of a permanent magnet type electromagnetic flowmeter using a liquid junction electrode according to the present invention, FIG. 2 is a sectional view showing a detailed configuration example of a liquid junction electrode, FIG. FIG. 3 is a circuit diagram showing an electrical system configuration example of a permanent magnet type electromagnetic flowmeter including a converter according to the present invention. 1 to 3, the same parts as those in FIGS. 5 and 6 are designated by the same reference numerals.

In FIG. 1, the fluid to be measured 1 having conductivity.
A pair of permanent magnets 2 so that a direct-current magnetic field is formed so as to be orthogonal to the flow direction in the measuring tube 2 (the lining 3 is installed on the inner wall as in the conventional case) in which
The measurement tubes 2 are arranged so that the measurement tubes 2 are sandwiched while supporting the magnets 3 and 24 by the magnetic body 25 serving as the feedback magnetic path.

Further, a pair of liquid-junction type electrodes 21 and 22 are airtightly attached at opposite positions on the tube wall on the direction lines perpendicular to the flow direction and the magnetic field. On the other hand, as shown in FIG. 2, the liquid junction electrodes 21 and 22 are provided in an electrode container 26 made of an insulating material such as glass or plastic.
Internal liquid with conductivity such as KCl (potassium chloride) solution 2
8 is put under pressure from the internal liquid replenishment / pressurizing port 31 at a pressure higher than atmospheric pressure. A liquid junction 27 made of porous ceramic or the like is provided at the tip of the electrode container 26, and a metal electrode 29 made of AgCl (silver chloride) or the like is used as the internal liquid 28. Electrode container 26 in a dipped form
It is attached airtightly.

The liquid junction electrodes 21 and 22 are
Is attached to the measuring tube 2 in such a manner as to maintain airtightness with a sealing material 30 such as a rubber O-ring so that the liquid junction 27 contacts the fluid to be measured 1.

On the other hand, as shown in FIG. 3, the portion including the converter generates a DC magnetic field by the pair of permanent magnets 23 and 24. Then, the electromotive force E induced in the fluid to be measured 1
Is taken out by a pair of metal electrodes 29, a DC amplifier 37 in a converter 36 amplifies the signal, and the output circuit 1
The signal is converted in 3 and finally output as a flow rate signal.

Next, the operation of the electromagnetic flowmeter of the present embodiment constructed as above will be described. The electromotive force E (as in the formula (1)) induced in proportion to the flow velocity V, the magnetic flux density B, and the tube inner diameter D of the fluid to be measured 1 is taken out through the liquid-junction electrodes 21 and 22, and the converter 36 The signal is amplified by the DC amplifier 37, converted into a signal by the output circuit 13, and finally output as a flow rate signal.

In this case, in the liquid junction electrodes 21 and 22, a conductive internal liquid 28 such as a KCl solution flows into the fluid to be measured 1 through the liquid junction 27 in very small amounts. The electrical continuity between the fluid to be measured 1 and the metal electrode 29 is maintained via the internal liquid 28, and the electromotive force induced in the fluid to be measured 1 is the metal electrode 29. Can be taken from.

Since the internal liquid 28 is always in contact with the metal electrode 29 and does not come into direct contact with the fluid to be measured 1, the contact potential at the interface of the metal electrode 29 fluctuates. Without it, the electromotive force E can be measured.

Therefore, it is possible to construct an electromagnetic flow meter using a DC magnetic field, and by using the permanent magnets 23 and 24, it is possible to realize a power saving type electromagnetic flow meter.
As described above, in the present embodiment, the magnetic field is applied to the fluid to be measured 1 having conductivity which flows in the measuring tube 2 so as to be orthogonal to the flow direction, and the electromotive force induced in the fluid to be measured 1 is measured. In an electromagnetic flowmeter for measuring the flow rate of the fluid to be measured 1 by taking out and detecting the fluid with a pair of electrodes, as the electrode, an internal fluid 28 having conductivity is replenished in an electrode container 26 made of an insulating material. In a form in which a liquid junction 27 made of a porous ceramic is provided at the tip of the electrode container 26 and a metal electrode 29 is dipped in the internal liquid 28 by applying pressure from the pressurizing port 31 at a pressure higher than atmospheric pressure. A liquid junction type electrode body, which is airtightly attached to the electrode container 26, is attached to the sealing material 3
The liquid junction 27 is attached to the measuring tube 2 so that the airtightness is maintained by 0.
Liquid-junction type electrode 2 attached so that it contacts the fluid to be measured 1.
1 and 22, a direct current magnetic field is applied as the magnetic field by using a pair of permanent magnets 23 and 24 arranged so as to sandwich the measuring tube 2.

Therefore, as an electrode for taking out the induced electromotive force, the liquid junction type electrode 21 having the conductive internal liquid 28,
Since 22 is used, the fluid 2 to be measured is a metal electrode 2
Internal liquid 2 which has conductivity without direct contact with itself 9
8 contacts the fluid to be measured 1 through the liquid junction 27, the metal electrode 29 always contacts the internal liquid 28, and the metal electrode 29 always contacts the internal liquid 28 under a certain condition. Since it has electrical continuity with the fluid to be measured 1 through 28 and the contact potential does not change depending on the type and state of the fluid to be measured 1, a DC magnetic field method, that is, an electromagnetic flow rate using the permanent magnets 23, 24. Therefore, it is possible to realize an inexpensive converter 36 that is power-saving and does not require an exciting circuit.

As described above, it becomes possible to save power and reduce cost by eliminating the need for an exciting circuit. The present invention is not limited to the above embodiment, but can be implemented in the same manner as described below.

(A) The liquid-junction type electrode applied to the present invention is not limited to the one shown in FIG. That is, as the liquid junction electrode, for example, as shown in the cross-sectional view of FIG. 4, the pressure of the fluid to be measured 1 and the pressure of the internal fluid 28 between the fluid to be measured 1 and the internal liquid 28 of the liquid junction electrodes 21 and 22. Pressure receiving part 3 composed of bellows etc. to balance with
8 may be provided to balance the pressure. Note that, in FIG. 4, the same parts as those in FIG. 2 are denoted by the same reference numerals.

Liquid pressure balanced type liquid junction type electrode 2
By using 1 and 22 as electrodes for extracting the induced electromotive force, when the pressure of the fluid 1 to be measured is high, the internal liquid 2
8 does not flow out of the liquid junction 27, and conversely the fluid to be measured 1
Can be prevented from entering.

(B) In the above embodiment, the case where the electromotive force induced in the fluid to be measured 1 is taken out by the pair of electrodes has been described, but the invention is not limited to this. The electrodes may be taken out by more than one pair of electrodes, and in this case, the measurement accuracy of the flow rate of the fluid 1 to be measured can be increased accordingly.

(C) In the above embodiment, the case where the DC magnetic field is applied using the pair of permanent magnets 23 and 24 arranged so as to sandwich the measuring tube 2 has been described, but the present invention is not limited to this. Alternatively, a pair of exciting coils may be arranged so as to sandwich 2, and a DC magnetic field may be applied by energizing this exciting coil from a DC exciting circuit.

[0031]

As described above, according to the present invention, a magnetic field is applied to a fluid to be measured having conductivity which flows in a measuring tube so as to be orthogonal to the flow direction of the fluid to be induced in the fluid to be measured. In an electromagnetic flowmeter that measures the flow rate of a fluid to be measured by extracting and detecting the electromotive force generated by a pair of electrodes, at least a pair of liquid junction electrodes having a conductive internal liquid are used as the electrodes, and further Depending on the above, a pressure receiving part for balancing the pressure of the fluid to be measured and the pressure of the internal fluid is attached between the fluid to be measured and the internal fluid of the liquid junction type electrode, so an excitation circuit is not required and it is saved. It is possible to provide an electromagnetic flow meter capable of reducing power consumption and cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a detector of a permanent magnet type electromagnetic flowmeter using a liquid junction electrode according to the present invention.

FIG. 2 is a cross-sectional view showing a detailed configuration example of a liquid junction electrode in the example.

FIG. 3 is a circuit diagram showing an electrical system configuration example of a permanent magnet type electromagnetic flow meter according to the present invention including a converter.

FIG. 4 is a cross-sectional view showing another configuration example of the liquid junction electrode according to the present invention.

FIG. 5 is a schematic diagram showing a principle configuration example of a detector of a conventional electromagnetic flow meter.

FIG. 6 is a circuit diagram showing a configuration example of an electric system of a conventional electromagnetic flowmeter including a converter.

[Explanation of symbols]

1 ... Fluid to be measured, 2 ... Measuring tube, 3 ... Lining, 13 ...
Output circuit 21,22 ... Liquid junction type electrode, 23, 24 ... Permanent magnet, 25 ... Magnetic body, 26 ... Electrode container, 27 ... Liquid junction part,
28 ... Internal liquid, 29 ... Metal electrode, 30 ... Sealant,
31 ... Internal liquid supply / pressurizing port, 36 ... Converter, 37 ... DC amplifier.

Claims (4)

[Claims] 1. A magnetic field is applied to a conductive fluid to be measured flowing in a measuring tube so as to be orthogonal to the flow direction, and electromotive force induced in the fluid to be measured is taken out and detected by a pair of electrodes. In the electromagnetic flowmeter for measuring the flow rate of the fluid to be measured, at least a pair of liquid-junction electrodes having a conductive internal liquid are used as the electrodes. 2. The electromagnetic flowmeter according to claim 1, wherein a pressure-receiving portion that balances the measured fluid pressure and the internal liquid pressure between the measured fluid and the internal liquid of the liquid junction electrode. An electromagnetic flowmeter characterized by being provided with. 3. The liquid junction electrode comprises a conductive internal liquid which is pressurized at a pressure of atmospheric pressure or higher into an electrode container made of an insulating material, and a porous ceramic is provided at a tip portion of the electrode container. And a liquid junction type electrode body configured by air-tightly attaching a metal electrode to the electrode container in a form of immersing the metal electrode in the internal liquid, and maintaining the air-tightness by a sealing material. The electromagnetic flowmeter according to claim 1 or 2, wherein the liquid junction is attached to the measurement tube so as to come into contact with the fluid to be measured. 4. The direct current magnetic field is applied as the magnetic field using a pair of permanent magnets arranged so as to sandwich the measurement tube. Electromagnetic flow meter.