JPH11325991A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electromagnetic flowmeter capable of making the same signal processing and same arithmetic operation with a single power source whether a fluid to be measured flows forward or reverse. SOLUTION: A flow judging means 10 for judging whether a fluid to be measured flows in a pipe line 1 forward or reverse and exciting means 11 for switching the direction of an exciting current flowing in exciting coils 9a, 9b according to the judging result of the judging means 10 showing the forward or reverse flow are provided. When the potential of one electrode 2a of a pair of electrodes 2a, 2b shows either the forward or reverse flow, it is made also higher than the potential from the other electrode 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a magnetic field to a fluid to be measured in a pipe by an excitation coil, detecting a flow signal generated by the Faraday's law of electromagnetic induction with an electrode, processing the signal, and performing signal processing. It relates to an electromagnetic flowmeter for measuring.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional electromagnetic flowmeter usually has a pair of electrodes 52 provided in a pipe 51 and a pipe 5 provided with a pair of electrodes 52.
An exciting current is applied from the exciting circuit 54 to the outer exciting coil 53 to apply a magnetic field to the fluid to be measured in the conduit 51. It is detected by the electrode 52 and output to the amplifier circuit 55. In the amplifying circuit 55, the difference between the two flow signals is (e1-e).
2), and is amplified, so that when the fluid to be measured flows forward (e
Assuming that the output of the amplifier circuit 55 is positive in 1> e2), the output of the amplifier circuit 55 is negative in reverse flow (e1 <e2).

Therefore, when the fluid to be measured is a positive flow, the positive output is converted into a digital signal by the A / D converter 56 and the arithmetic circuit 5
7, and in the case of backflow, the negative output is A / D
The digital conversion is performed by the converter 56 and the arithmetic processing is performed by the arithmetic circuit 57. The calculation result is output from the output circuit 58.

[0004]

As described above, in the conventional electromagnetic flowmeter, when the fluid to be measured can be measured in the forward flow and the reverse flow, the flow signal obtained from the electrode 52 is amplified by the amplification circuit 5.
The output value amplified in step 5 requires a wide range of signal processing and arithmetic processing from positive to negative. With negative signal processing, it is necessary to prepare both positive and negative power supplies. For example, when a battery is used as a power source, a negative battery, which is hardly used in a normal installation, must be secured with the same capacity as the positive battery, so that the number of batteries cannot be reduced.

An object of the present invention is to provide an electromagnetic flowmeter capable of performing the same signal processing and the same arithmetic processing with a single power supply, regardless of whether the fluid to be measured is flowing forward or backward. To provide.

[0006]

The invention according to claim 1 is
An excitation current having a non-excitation period is applied to the excitation coils 9a and 9b, and a magnetic field due to the excitation current is applied to the fluid to be measured flowing in the pipeline 1. In an electromagnetic flow meter that detects the flow rate through 2b and processes the signal by the signal processing means 5 to measure the flow rate
Forward / reverse determining means 10 for determining whether the fluid to be measured flowing in the pipeline 1 is a forward flow or a backward flow;
Exciting means 11 for switching the direction of the exciting current flowing through the exciting coils 9a and 9b depending on whether the determination result of 0 is a positive flow or a reverse flow.

[0007] As described above, the excitation coil 9 differs depending on whether the fluid to be measured flowing in the pipe 1 is a normal flow or a reverse flow.
When the direction of the exciting current flowing through the electrodes a and 9b is switched, a magnetic field corresponding to the direction of the flow is applied to the fluid to be measured, so that one electrode 2a of the pair of electrodes 2a and 2b
Is always higher than the potential of the other electrode 2b, so that the fluid to be measured is either a normal flow or a reverse flow,
The same signal processing and the same arithmetic processing are required.

According to a second aspect of the present invention, based on the first aspect of the present invention, the forward / reverse determining means 10 includes a pair of electrodes 2a and 2a.
It is characterized in that it is determined from the change of the flow signal detected via the line b whether the flow is the normal flow or the reverse flow.

In such a case, the direction of the exciting current flowing through the exciting coils 9a and 9b can be determined without separately providing flow direction detecting means for detecting the forward flow and the reverse flow of the fluid to be measured. Can be automatically switched by a feedback system.

According to a third aspect of the present invention, based on the first aspect of the present invention, the flow rate signal is detected stably by improving the concentration and directivity of the magnetic flux with respect to the axis of the pipeline 1.
It is characterized in that a pair of exciting coils 9a and 9b are arranged to face each other outside the pipeline 1, and an exciting current is supplied to these exciting coils 9a and 9b by the exciting means 11 at the same time.

According to a fourth aspect of the present invention, in order to reduce current consumption as compared with the third aspect of the invention, the exciting means 11 allows the exciting current to flow independently of only one of the pair of exciting coils 9a and 9b. It is characterized by being able to do.

According to a fifth aspect of the present invention, based on the first aspect of the present invention, the exciting coil 9a is provided only on one side outside the conduit 1 in order to reduce costs, facilitate processing, and reduce size. It is characterized by.

The invention according to claim 6 has the disadvantage that the magnetic flux concentration and directivity are poor if the excitation coil 9a is installed only on one side outside the pipeline 1 as in the invention of claim 5. In order to compensate for this and detect a stable flow signal, a magnetic circuit is formed outside the pipe 1 between the core 12a of one excitation coil 9a and the opposite side with the pipe 1 interposed therebetween. And a magnetic circuit 13 for circulating a magnetic flux passing through the pipe 1.

The invention according to claim 7 is characterized in that one of the pair of electrodes 2a and 2b is made equal to the ground potential of the signal processing means 5 in order to improve the accuracy of signal processing. The present invention can be applied to the inventions of (6) to (6).

[0015]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration common to all of the embodiments described later of the present invention. In FIG. 1, a pair of electrodes 2 a and 2 b are arranged in a conduit 1 so as to face each other on a line orthogonal to the axis of the conduit 1. The flow rate signals detected by these electrodes 2a and 2b
After signal processing, that is, amplification and digital conversion by the signal processing means 5 and the A / D converter 4, calculation is performed by the calculation means 6, and the calculation result is output from the output means 7. The signal processing means 5, the arithmetic means 6, and the output means 7 operate on a single power supply 8.

FIG. 2 shows a first embodiment of the present invention. In this electromagnetic flow meter, a pair of exciting coils 9 a and 9 b are opposed to the outside of the pipe 1 with the axis of the pipe 1 interposed therebetween. In addition to the means shown in FIG. 1, a forward / reverse determining means 10 and an exciting means 11 are provided.

Core 12a of a pair of exciting coils 9a and 9b
12b is opposed on a line orthogonal to a line connecting the pair of electrodes 2a and 2b, and the two exciting coils 9a and 9b
Generates a magnetic field in a direction orthogonal to a line connecting the pair of electrodes 2a and 2b.

The forward / reverse determining means 10 includes a pair of electrodes 2a and 2
b, it is determined whether the flow of the fluid to be measured in the pipeline 1 is a normal flow or a reverse flow from the change in the flow rate signal processed by the signal processing means 5 and the result of the determination is calculated. The means 6 and the exciting means 11 are notified.

The exciting means 11 is provided with an exciting coil 9a, 9 when the determination result of the forward / reverse determining means 10 is a forward flow or a reverse flow.
The direction of the exciting current flowing through b is switched.

In the electromagnetic flow meter shown in FIG.
A case where the fluid to be measured flows in the inside from the front to the back of the paper is defined as a normal flow, and a case where the fluid to be measured flows from the back of the paper to the front in the reverse direction is a reverse flow. Now, in the case of a positive flow, the excitation coil 9a
Assuming that an exciting current having a non-excitation period is simultaneously supplied to the fluid to be measured from the core 12a to the core 12b in the direction of the core 12a, the electrode 2a is applied to the electrode 2a according to Faraday's law of electromagnetic induction. A flow signal voltage proportional to the flow rate of the fluid to be measured is generated at 2b. In this case, the potential of the electrode 2a is higher than the potential of the electrode 2b.

When the flow of the fluid to be measured in the pipe line 1 changes from a forward flow to a backward flow, and this is determined by the forward / reverse determining means 10, the exciting means 11 connects the exciting coils 9a and 9b to the exciting coils 9a and 9b. The flowing current is switched in the direction opposite to that in the normal flow. Therefore, in this case, a magnetic field in which a magnetic flux flows from the core 12b to the core 12a is applied to the fluid to be measured, and the flow rate between the electrodes 2a and 2b is proportional to the flow rate of the fluid to be measured according to Faraday's law of electromagnetic induction. A signal voltage is generated. Also in this case, the potential of the electrode 2a is higher than the potential of the electrode 2b.

As described above, regardless of whether the flow of the fluid to be measured in the pipe line 1 is a forward flow or a reverse flow, the flow signal voltage generated between the electrodes 2a and 2b is equal to the potential of the electrode 2a. Of the two electrodes 2a and 2b
The signal processing means 5 for performing signal processing on the flow rate signal detected in step 1 and the calculating means 6 for performing calculation do not need to process both positive and negative signals, and may have a single configuration that only requires processing of positive signals. It can be operated with a single power supply consisting only of a power supply.

FIG. 3 shows that the exciting coil 9a is provided only on one side of the conduit 1.
Is installed, and the current flowing through this one exciting coil 9a is
An embodiment is shown in which switching is performed between the forward flow and the reverse flow of the fluid to be measured in the same manner as in the example of FIG. Even in such a case, the flow signal voltage generated between the electrodes 2a and 2b is higher in the potential of the electrode 2a than the potential of the electrode 2b in either the forward flow or the reverse flow.

As shown in FIG. 3, when the exciting coil 9a is provided only on one side of the pipe 1, the structure becomes simple, but the core 12
There is a disadvantage that the magnetic flux from a diverges and the concentration and directivity of the magnetic flux are poor. In order to compensate for this, the embodiment of FIG. 4 forms a magnetic circuit outside the pipe 1 between the core 12a of the exciting coil 9a and the opposite side of the pipe 1 with the pipe 1 interposed therebetween. A magnetic circuit 13 is provided for circulating the magnetic flux passing therethrough. The magnetic circuit body 13 is installed so as to go around the pipeline 1, and the core 12 on the opposite side to the pipeline 1 is provided.
An end face a is magnetically connected to the core 12a, and a protruding portion 14 is provided on the opposite side to the core 12a with the pipe 1 interposed therebetween.

In FIG. 4, when the flow of the fluid to be measured in the pipeline 1 is a positive flow, an exciting current flows through the exciting coil 9a, and a magnetic field is generated from the core 12a in the direction of the protrusion 14. The magnetic flux traversing the pipeline 1 circulates from the protrusion 14 through the magnetic circuit 13 in the direction of the solid arrow.
In the case of FIG. 3, the magnetic flux in the conduit 1 diverges away from the core 12a. However, if the projecting portion 14 is provided on the opposite side to the core 12a, the magnetic flux converges on this.
A stable flow signal voltage can be detected as compared with the case of.

In FIG. 4, when the flow of the fluid to be measured in the conduit 1 is reverse, an exciting current flows through the exciting coil 9a in a direction opposite to that in the forward flow, and a magnetic field is generated from the protrusion 14 to the core 12a.
, The magnetic flux traversing the pipeline 1 circulates through the magnetic circuit 13 in the direction of the dotted arrow.

Therefore, in the flow signal voltage generated between the electrodes 2a and 2b, the potential of the electrode 2a is higher than the potential of the electrode 2b in either the forward flow or the reverse flow. Similarly to the case, the signal processing unit 5 and the arithmetic unit 6 do not need to process both positive and negative signals, and may have a single configuration in which only the positive signal is processed. Can be done.

FIG. 5 shows one of the pair of electrodes 2a and 2b 2b.
Is equal to the ground potential of the signal processing means 5 and the operation is performed in the same manner as in the case of FIG. In this way, the electrode 2b, which is always at a low potential, has the same potential as the reference value of the signal processing means 5, so that signal processing is facilitated and the accuracy is improved. When only one of the pair of exciting coils 9a and 9b is supplied with an exciting current independently, current consumption can be reduced.

[0030]

According to the first aspect of the present invention, the direction of the exciting current flowing through the exciting coil is switched between a case where the fluid to be measured flowing in the pipeline is a normal flow and a case where the fluid to be measured flows in the reverse direction. Since a magnetic field corresponding to the direction of the flow is applied to the fluid, the potential from one of the pair of electrodes is higher than the potential of the other electrode in either a positive or reverse flow. When the potential becomes high and the fluid to be measured flows forward or backward, the same signal processing and the same arithmetic processing can be performed, and the operation can be performed by a single power supply signal processing.

According to the second aspect of the present invention, it is determined whether the flow is a normal flow or a reverse flow based on a change in the flow signal detected through the pair of electrodes. In addition, there is an effect that the direction of the exciting current flowing through the exciting coil can be automatically switched by the feedback system without separately preparing a flow direction detecting means for detecting the normal flow and the reverse flow of the fluid to be measured. .

According to the third aspect of the present invention, a pair of exciting coils are arranged opposite to each other outside the pipeline, and an exciting current is simultaneously supplied to these exciting coils by exciting means.
In addition to the effects of the invention according to the above, there is an effect that the concentration and the directivity of the magnetic flux with respect to the axis of the pipeline are improved and a stable flow signal can be detected.

According to the fourth aspect of the present invention, since only one of the pair of exciting coils allows the exciting current to flow independently, the effect of reducing the current consumption can be obtained in addition to the effect of the first aspect of the present invention. is there.

According to the fifth aspect of the present invention, since the exciting coil is installed only on one side outside the pipeline, in addition to the effects of the first aspect of the present invention, cost reduction, ease of processing and miniaturization can be achieved. There is an effect that can be achieved.

According to the invention of claim 6, a magnetic circuit is formed outside the conduit between the core of one excitation coil and the opposite side of the conduit with the magnetic flux passing through the conduit. However, if the magnetic circuit body is provided on only one side outside the pipeline as in the invention of claim 5, there is a disadvantage that the concentration and the directivity of the magnetic flux are poor. This has the effect that a stable flow signal can be detected.

According to the seventh aspect of the present invention, one of the pair of electrodes is made equal to the ground potential of the signal processing means. In addition to the effect of the first aspect of the present invention, the signal processing is facilitated. There is an effect that accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration common to all embodiments of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention using a pair of excitation coils.

FIG. 3 is a schematic configuration diagram of a main part of an embodiment of the present invention using one excitation coil.

FIG. 4 is a schematic configuration diagram of a main part of an embodiment of the present invention using a magnetic circuit.

FIG. 5 is a schematic configuration diagram of a main part of an embodiment of the present invention in which one of a pair of electrodes is equal to a ground potential of a signal processing unit.

FIG. 6 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipeline 2a ・ 2b Electrode 3 Amplification circuit 4 A / D converter 5 Signal processing means 6 Calculation means 7 Output means 8 Single power supply 9a ・ 9b Excitation coil 10 Forward / reverse determination means 11 Excitation means 12a ・ 12b Core 13 Magnetic circuit 14 Protrusion

Claims (7)

[Claims] An exciting current having a non-excitation period is applied to an exciting coil, and a magnetic field due to the exciting current is applied to a fluid to be measured flowing in a pipeline. In an electromagnetic flowmeter that detects through an electrode and measures a flow rate by processing a signal with a signal processing unit, a forward / reverse determination unit that determines whether a fluid to be measured flowing in the pipeline is a forward flow or a backward flow. And an exciting means for switching the direction of the exciting current flowing through the exciting coil depending on whether the determination result of the forward / reverse determining means is a forward flow or a reverse flow. 2. The apparatus according to claim 1, wherein the forward / reverse determining unit determines whether the flow is normal or reverse based on a change in the flow signal detected via the pair of electrodes. Electromagnetic flowmeter. 3. The electromagnetic flowmeter according to claim 1, wherein a pair of exciting coils are arranged outside the conduit so as to face each other, and said exciting means simultaneously supplies an exciting current to these exciting coils. 4. A pair of exciting coils are arranged opposite to each other outside the pipeline, and said exciting means includes one of said pair of exciting coils.
The electromagnetic flowmeter according to claim 1, wherein the excitation current can flow independently of only the number of pieces. 5. The electromagnetic flowmeter according to claim 1, wherein the exciting coil is provided only on one side outside the pipeline. 6. A magnetic circuit is formed outside the conduit between the core of the exciting coil and the opposite side of the conduit with the conduit interposed therebetween, and a magnetic circuit body for circulating magnetic flux passing through the conduit is provided. The electromagnetic flowmeter according to claim 5, characterized in that: 7. The method according to claim 1, wherein one of the pair of electrodes is made equal to the ground potential of the signal processing means.
The electromagnetic flowmeter according to 2, 3, 4, 5, or 6.