JPH0228408Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> The present invention relates to an electromagnetic flowmeter transmitter (hereinafter abbreviated as a transmitter when necessary), and is particularly useful when the distance between the surfaces of the transmitter is shortened. This has been improved to eliminate the problems that arise.

<Prior Art> There is a so-called weighting function as an index that indicates the proportion of voltage that is contributed to the signal detection electrode when a unit voltage is applied to an arbitrary point inside the conduit of the transmitter. This weighting function has a maximum value at the cross section of the conduit that includes the signal detection electrode, and tends to decrease sharply as it moves away from this in the axial direction of the conduit. The length in the axial direction of the tube that hardly contributes to the signal detection electrode is approximately 0.75D upstream and downstream from the conduit cross section including the signal detection electrode, where D is the inner diameter of the conduit. Therefore, the length of the conventional transmitter in the tube axis direction, that is, the distance between the surfaces, is about 1.5D.

However, in recent years, electromagnetic flowmeters have tended to be made smaller in pursuit of economic efficiency and weight reduction, and at the same time, high accuracy is also required. In order to achieve miniaturization, it is necessary to make the distance L between the surfaces of the transmitter shorter than the inner diameter D. FIG. 1 shows the distribution of electric lines of force within a conduit when the distance between the surfaces of a conventional transmitter is simply shortened. In FIG. 1, magnetic field generating means such as excitation coils are omitted.
Reference numeral 1 denotes a transmitter conduit, the inner surface of which is lined with a lining 2. 3a and 3b are signal detection electrodes that detect signal voltages generated by flowing fluid. 4a and 4b are pipes into which the transmitter 5 is inserted, and each is grounded at G.
When a magnetic field is applied to the fluid to be measured 6 and the fluid to be measured flows in the direction of arrow F, a signal voltage corresponding to the flow rate is generated at the detection electrodes 3a and 3b and detected by a converter (not shown). In this case, the electric lines of force generated in the fluid to be measured 6 are a group of electric lines of force 7, 7a ₁ , 7a ₂ . . . 7a _o , 7 that go directly from the detection electrode 3a to the detection electrode 3b.
b ₁ , 7b ₂ . _. . _{7b o} and 8a _{1 ,} . be.
When the inter-plane distance L of the transmitter 5 is longer than the inner diameter D, the electric force line groups 8a ₁ ,...8a ₄ , 8b ₁ , 8b ₄ do not exist, and the electric force line groups 7, 7a ₁ , 7a ₂ ...7a _o , 7
b ₁ , 7b ₂ ... only 7b _o . However, the distance L between the surfaces
becomes shorter than the inner diameter D, the mating pipes 4a, 4
Groups _of electric lines _of force 8a _{1 ,} . As the inter-plane distance L becomes shorter than the inner diameter D, the number of electric lines of force increases. Electric field lines group 8
a ₁ ,...8a ₄ , 8b ₁ , 8b ₄ are signal detection electrodes 3a, 3
Since it flows into and out of b, fluctuations in this will cause a span error. Specifically, if the materials of the mating pipes 4a and 4b are different or the conductivity of the inner surface of the mating pipes changes, the electric force line groups 8a ₁ , ... 8a ₄ , 8b ₁ , 8b ₄
The short-circuit condition changes, causing span fluctuations. This short-circuit effect is such that the lower the conductivity of the fluid 6 to be measured, the more lines of electric force short-circuit to the inner surfaces of the conductive pipes 4a and 4b, which greatly reduces the signal voltage and increases errors.

<Purpose of the invention> In view of the above-mentioned prior art, the present invention aims to eliminate span errors caused by changes in the type of mating piping and changes in the conductivity of the fluid to be measured, which occur with downsizing.

<Structure of the invention> The structure of the invention that achieves this object includes a conduit whose inner surface is lined with an insulating material, a means for generating a magnetic field in a direction perpendicular to the axis of the conduit, and a means for generating a magnetic field between the axis of the conduit and the magnetic field. an electromagnetic flowmeter transmitter having a cross section perpendicular to the axis of the conduit including the signal detection electrode and a signal detection electrode disposed in a conduit so as to face each other in a direction perpendicular to the electromagnetic flowmeter transmitter; It is characterized in that an annular conductor is disposed on the inner wall of the lining between the end surface of the container and the inner wall of the lining.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings. Note that parts having the same functions as those in FIG. 1 are denoted by the same reference numerals, and redundant explanations will be omitted.

FIG. 2 is a sectional view of a transmitter showing one embodiment of the present invention. Only the conduit section of the transmitter and the piping section connected thereto are shown. In FIG. 2, annular conductors 9a and 9b are arranged on the inner surface of the lining 2, which is symmetrical with respect to the cross section of the conduit including the signal detection electrodes 3a and 3b. This conductor 9
a, 9b are not grounded and are insulated from the conduit. With this configuration, most of the electric lines of force generated due to the flow of the fluid to be measured are directed from the signal detection electrodes 3a to 3b in the group of electric lines of force 10a ₁ ...10
a _o , 10b ₁ ...10b _o , but some electric lines of force 1
1a ₁ and 11b ₁ enter the conductors 9a and 9b, pass through them, and then flow into the signal detection electrode 3b as electric lines of force 11a ₂ and 11b ₂ . These conductors 9a, 9b
Since this is not grounded, the current that enters here does not flow into the conduit 1 or the pipes 4a and 4b. Therefore, there is no reduction in signal voltage due to short circuit effects. In other words, in FIG. 1, where the distance between the surfaces of the conventional transmitter is simply shortened, the electric force line groups 8a ₁ , ... 8a ₄ , 8b ₁ , 8b ₄ that would have conventionally flowed into the mating pipes are changed in this embodiment. Since it is absorbed by the conductors 9a and 9b, it is not affected by the mating pipes 4a and 4b.

In the embodiment shown in Fig. 2, one conductor ring is installed between the conduit cross section including the signal detection electrode and the end face of the transmitter, but two or more conductor rings may be installed. It's okay.

Further, the conductor shown in FIG. 2 is not limited to a metal body, and may be any electrically conductive body. For example, the same effect can be obtained by mixing a conductive substance into a part of the insulating lining and making only the annular part a conductive plastic.

<Effects of the Invention> As described above in detail along with the embodiments, according to the present invention, the short circuit effect caused by the mating piping can be reduced by simply arranging a non-grounded annular conductor on the inner surface of the insulating lining. This has the effect of making it possible to obtain a transmitter between short surfaces at a low cost, which is less susceptible to radiation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional transmitter;
FIG. 2 is a sectional view showing an embodiment of the present invention. 1... Conduit, 2... Lining, 3a, 3b...
... Signal detection electrode, 4a, 4b ... Piping, 5 ... Transmitter, 7, 7a ₁ ... 7a _o , 7b ₁ ... 7b _o ... Line of electric force, 8a ₁ , ... 8a ₄ , 8b ₁ , 8b ₄ ... …Electric lines of force, 9
a, 9b...conductor, 10,10a ₁ ...10a _o , 1
0b ₁ ...10b _o ...Electric field lines, 11a ₁ , 11a ₂ , 1
1b ₁ , 11b ₂ ... Lines of electric force.

Claims (1)

[Scope of utility model registration request] a conduit whose inner surface is lined with an insulating material, and means for generating a magnetic field in a direction perpendicular to the axis of the conduit;
In an electromagnetic flowmeter transmitter having a signal detection electrode disposed in a conduit facing each other in a direction perpendicular to the axis of the conduit and the magnetic field, the signal detection electrode is perpendicular to the axis of the conduit including the signal detection electrode. An electromagnetic flowmeter transmitter, characterized in that an annular conductor is disposed on the inner wall of the lining between the cross section and the end face of the electromagnetic flowmeter transmitter.