JPH06229795A - Electromagnetic flowmeter for unfilled pipe line - Google Patents

Abstract

PURPOSE:To eliminate fluctuation in conductivity of fluid and fluctuation in sensitivity due to adherend to an electrode. CONSTITUTION:A pipe line l is made of a material having high electric resistance thus establishing electrical capacitive coupling between fluid and electrodes 2, 2. Even if the conductivity of fluid varies or a matter having conductivity different from that of the fluid adheres to the electrode, the impedance at the interface of the electrode and the fluid is balanced with the impedance of the fluid and not effected adversely thus providing a stabilized measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flow meter for measuring the flow rate of a fluid flowing down in a pipe line in a full or non-full state.

[0002]

2. Description of the Related Art The applicant has proposed an electromagnetic flow meter for non-filling water which measures the flow rate of a fluid flowing in a pipe line in a non-filling state using the principle of an electromagnetic flow meter (Japanese Patent Application No. 3-335050).

This prior art has exciting coils arranged above and below the conduit respectively, and by changing the combination of excitation of these exciting coils, a spatially different non-uniform first
And a second magnetic flux density distribution during different time periods. Then, the electromagnetic flowmeter for non-full water is based on the principle of calculating the flow rate of the pipeline based on the flow rate signals generated respectively in the first and second magnetic flux density distributions.

[0004]

SUMMARY OF THE INVENTION In the above conventional technique,
The sensitivity of the flow meter changes as the balance between the impedance of the interface between the electrode and the fluid and the impedance of the fluid changes.

For example, when the conductivity of the fluid to be measured changes, the impedance of the fluid and the impedance of the interface between the electrode and the fluid change at different rates under the influence of the change, resulting in a sensitivity change and a flow rate change. There is a problem that an error occurs in the measurement.

Further, when a substance having a conductivity different from that of the fluid to be measured adheres to the electrode, the impedance of the different surface between the electrode and the fluid changes, resulting in a change in sensitivity, which causes an error in flow rate measurement. there were.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electromagnetic flowmeter for non-full water which can solve these problems.

[0008]

In order to achieve the above object, the non-full-water electromagnetic flowmeter of the present invention has exciting coils arranged above and below the conduit, respectively. By changing the combination, the spatially different first and second magnetic flux density distributions are generated during different periods, and the flow path signals generated during the first and second density distributions An electromagnetic flowmeter for calculating a flow rate, characterized in that a material having a high electric resistance is interposed between an electrode and a fluid to be measured.

[0009]

[Function] Since the electrode is capacitively coupled, the impedance at the interface between the electrode and the fluid becomes extremely large, and the balance between the impedance at the interface and the impedance at the fluid is disrupted in the case of normal fluid conductivity changes and deposits. And these adverse effects are virtually eliminated.

[0010]

Embodiment 1 In the embodiment of FIG. 1, 1 is a pipe made of a cylindrical high-resistance material, and a pair of counter electrodes 2 on both left and right sides thereof.
2 is attached.

As the high resistance material forming the conduit 1, a material whose electric resistivity (specific resistance) is much larger than the specific resistance of the fluid to be measured or the electrodes is used. It is electrically capacitively coupled to the fluid via the resistance material.

U and L are exciting coils respectively arranged on the upper side and the lower side of the conduit 1, and are excited by the exciting power source 3 in a predetermined combination of two kinds. For example, the upper excitation coil U
Alone (A) and the vertical excitation coil U. Excitation is performed in a combination of L simultaneous (B).

A flow rate signal (output voltage of the amplifier circuit 4) E corresponding to each excitation combination (A) and (B)
_A and E _B are A / D converted and taken into the arithmetic circuit 6. Reference numeral 5 is an A / D conversion circuit.

Reference numeral 7 is a timing circuit for generating a timing signal to be sent to the exciting power source 3, the A / D conversion circuit 5 and the arithmetic circuit 6. The ratio E _B / E _{A of the} flow rate signals E _B and E _A , and the conduit line. Since there is a relationship as shown by the curve a in FIG. 2 with the water level h of the fluid flowing down, the water level h is obtained from the flow rate signals E _A and E _B.
I understand.

Specifically, in the memory 8 of FIG. 1, the ratio E _B /
_A reference table of the value of E _{A and} the value of the water level h is stored, and the water level h is obtained from this control table. The water level h on the horizontal axis in FIG.
Is graduated in proportion to the inner diameter D of the conduit.

When the sensitivity k of the electromagnetic flowmeter for non-full water is defined as k = flow rate / flow rate signal E _A , the sensitivity k is determined by the water level h, and is represented by the curve B in FIG.

The memory 8 also stores a comparison table between the water level h and the sensitivity k corresponding to FIG.
And the flow rate Q is set to Q = k · E _A and calculated by the arithmetic circuit 6.

The memory 8 also stores these arithmetic programs. The calculated flow rate Q is output from the output circuit 9 to the output terminal 10 in an appropriate form as a flow rate output.

[0019]

Since the electromagnetic flowmeter for non-full water of the present invention is constructed as described above, the fluid and the electrode are electrically capacitively coupled, and the impedance at the interface between the electrode and the fluid and the impedance of the fluid are Since the balance is not affected by the change in conductivity of the fluid or the deposit on the electrode, a stable flow rate measurement value can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a water level vs. output ratio diagram.

FIG. 3 is a water level vs. sensitivity diagram.

[Explanation of symbols]

 1 Pipeline made of material with high electric resistance 2 Electrodes U, L Excitation coil

Claims (1)

[Claims] 1. Exciting coils respectively arranged above and below the conduit are provided, and by changing the combination of excitation of these exciting coils, spatially different first and second magnetic flux density distributions of different periods can be obtained. An electromagnetic flowmeter for calculating the flow rate of a pipe line based on a flow rate signal generated during the first and second density distributions, which is generated between the electrode and the fluid to be measured. Electromagnetic flowmeter for non-filled water, characterized by the presence of high material.