JP2894011B2 - Electromagnetic flow meter detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance detection type in which a flow signal induced in a fluid to be measured is detected by a signal generated at a detection electrode arranged at a predetermined interval without directly contacting the fluid to be measured. More particularly, the present invention relates to an electromagnetic flowmeter detector improved so as to reduce the output impedance of the detector by minimizing the distance between the fluid to be measured and the detection electrode.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram including a conventional electromagnetic flow meter detector disclosed in Japanese Utility Model Application Laid-Open No. 56-137024, "Capacity detecting type electromagnetic flow meter". The outline of the electromagnetic flow meter detector will be described below.

[0003] On a pipe 11 formed of an insulating lining material through which a fluid to be measured flows, electrode plates 12 and 13 having a predetermined area around the axis thereof are arranged to face each other. Although not shown here, an exciting coil is also provided, and an electromotive force is generated in the measured fluid in accordance with the magnetic field generated by the exciting coil and the flow rate of the measured fluid flowing inside the pipe 11. ing. This electromotive force is extracted to the outside via capacitances C ₁ and C ₂ formed between the electrode plates 12 and 13 and the fluid to be measured.

[0004] The capacitances C _1, C _2, since generally is a very small value, the signal source Inpi - dancing is very high, high input Inpi vicinity of the electrode from the need to facilitate this for signal processing - Dance And the output signals of these amplifiers 14 and 15 are fed back to shields 16 and 17 on the input side of a shielded line for extracting signals, thereby reducing the influence of stray capacitance. .

In order to mount the electrode plates 12 and 13, concave portions are formed around a part of the outer peripheral surface of the pipe 11, and the electrode plates 12 and 13 are respectively arranged on the bottom surface of each concave portion and adhered. The outsides of these electrode plates 12 and 13 are covered with insulating covers 18 and 19. On the outer surface of the pipe 11 including these covers 18 and 19, a shield 2 is provided.
1, 22 are arranged, which are respectively shields 16,
17 and a signal line is guarded.

Here, when the pipe 11 is slightly deformed due to pressure fluctuation and temperature change of the fluid to be measured, the electrode plates 12, 1
3 is peeled off, thereby changing the capacitances C ₁ and C ₂ formed with the fluid to be measured, so that correct measurement cannot be performed. Therefore, as shown in FIG.
3, small holes 24, 25 are formed in a distributed manner, and the lining materials on both sides of the electrode plates 12, 13 are connected to each other through the small holes 24, 25.

FIG. 5 shows a detailed configuration of the electrode plate 13. Electrode plate 13 and pipes 11 on both sides and cover
In the case where the adhesive 19 is bonded, the adhesive is positioned in the hole 25 so as to be bonded to each other. When the electrode plate 13 and the cover 19 are integrally embedded in the pipe 11 as a mold, the lining material passes between the holes 25 and is integrally formed with the lining materials on both sides thereof, so that they are firmly connected to each other. Be linked.

[0008]

SUMMARY OF THE INVENTION However, the above
Fix the electrode plates 12 and 13 in the pipe 11
In such a structure, the distance between the electrode plates 12 and 13 and the fluid to be measured is
There is a limit to reducing the
Electrostatic capacitance C formed between electrode plates 12 and 13 ₁, C
_TwoSignal processing becomes difficult, and signal processing becomes difficult.
An electrode having a different thermal expansion coefficient from the pipe 11
Noise caused by displacement due to the use of plates 12 and 13
There is a problem that it is easy to make the cause.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electromagnetic flowmeter detector of a capacitance detection type, wherein an inner surface on the side through which a fluid to be measured passes is formed in a porous shape. A pipe composed of the lining material, a detection electrode surface thinly fixed to a part of this inner surface by metallization, and a part of the lining material penetrating part of the lining material to form an outer surface integrally with the lining material A flow signal is taken out from the conductive part provided with a conductive part provided and an insulating coating material that thinly covers the entire surface including the inner surface of the liner and the detection electrode surface. is there.

[0010]

[Operation] The pipe is made of a porous lining material on the inner surface on the side through which the fluid to be measured passes.
The detection electrode surface is thinly fixed to a part of the inner surface by metallizing. Further, a conductive portion is formed to penetrate a part of the lining material and to the outer surface integrally with the lining material. The entirety of the lining material including the inner surface and the detection electrode surface is electrically insulated. It is covered thinly with ting material.

Therefore, the detection electrode surface and the pipe are integrally formed, and the capacitance formed between the fluid to be measured and the detection electrode surface can be reduced, thereby simplifying the signal processing. Further, since the detection electrode surface formed by metallization can be made extremely thin, the amount of displacement due to temperature expansion can be reduced, and the fluctuation of temperature, pressure, and the like becomes strong.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the configuration of one embodiment of the present invention.

Reference numeral 30 denotes a cylindrical pipe having a thickness of t ₁ made of, for example, insulating ceramics.
A pair of cylindrical conductive portions 31 and 32 penetrating the pipe 30 are provided on both side surfaces facing the axis of the pipe 30.
Are formed. These conductive portions 31 and 32 have a configuration in which, for example, platinum powder is mixed with ceramics to impart conductivity, and are formed integrally with a ceramics pipe 30 while maintaining airtightness. .

The entire inner surface of the pipe 30 is formed in a porous shape. Of these, the lengths are L ₁ and L ₂ in the circumferential direction around the conductive parts 31 and 32, and the width of the pipe 30 in the axial direction is A large area having the size of W ₁ and W ₂ (not shown) is subjected to, for example, platinum metallization and baked to form conductive detection electrode surfaces 33 and 34 having a small thickness. In this way, these detection electrode surfaces 33 and 34 are electrically connected to the conductive portions 31 and 32, respectively.

The entire inner surface of the pipe 30 including the detection electrode surfaces 33 and 34 is made of an insulating thin film (for example, PFA (ethylene perfluoroalkyl vinyl ether copolymer resin)). Sa: coating material 35 of t ₂ )
Covered with. Since the coating material 35 has a porous inner surface of the pipe 30, the coating material 35 enters into these many holes, and the coating material 35 is formed on the inner surface of the pipe 30. Locked firmly.

[0016] At this time, co - if Teingu material 35 selected and the dielectric constant of the large PVdF Toka T _i O ₂ as the capacitance C ₃ between the sensing electrode surface 33 and the fluid to be measured,
C ₄ can be reduced. Reference numerals 36 and 37 denote lead foils for detecting signal voltages. The lead foils are connected to the conductive portions 31 and 32 at the outer ends of these lead foils 36 and 37, respectively. Metalized pipe 30
Has been raised to the upper end. Lead foil 36, 3 at upper end
Reference numeral 7 is connected to the core wires of the shield signal lines 38 and 39, respectively.

Reference numerals 40 and 41 denote guard electrodes for guards. These guard electrodes 40 and 41 correspond to detection electrode surfaces 33 and 41, respectively.
34, the lead foils 36, 37, etc.
Further, they are connected to shield portions of the shield signal lines 38 and 39. As a result, the potential is set to the same as that of the core wires of the shield signal lines 38 and 39, and the influence of the stray capacitance existing between the detection electrode surfaces 33 and 34 and the lead foils 36 and 37 is removed.

In the above description, ceramics is used as the pipe 30. However, plastics may be used instead.

[0019]

As described above, according to the present invention, the inner surface of the pipe is formed in a porous shape, and a thin detecting electrode surface is formed in the central portion by metallizing. In addition to strengthening the adhesive force, it is unlikely to cause noise even if there is a change in temperature or pressure.In addition, the inside surface of the pipe including the detection electrode surface is covered with a thin insulating coating material, so that the measured The capacitance formed between the fluid and the detection electrode surface can be increased, so that the impedance between them can be greatly reduced and the signal can be easily detected. Furthermore, even if the coating material is worn and the detection electrode surface comes in contact with the liquid, the flow measurement can be continued as it is as a liquid contact type detection electrode.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the configuration of one embodiment of the present invention.

FIG. 2 is a plan view of the embodiment shown in FIG. 1 as viewed from above.

FIG. 3 is a longitudinal sectional view showing a conventional capacity detection type electromagnetic flow meter.

4 is a cross-sectional view showing a configuration near a pipe of the electromagnetic flow meter shown in FIG.

5 is a perspective view showing the configuration of the electrode plate shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Pipe 12,13 Electrode plate 14,15 Amplifier 16,17 Shield 18,19 Cover 21,22 Shield 30 Pipe 31,32 Conducting part 33,34 Detection electrode surface 35 Lining material 36,37 lead Foil 40, 41 Guard electrode

Claims (1)

(57) [Claims] 1. A pipe made of a lining material having a porous inner surface on the side through which a fluid to be measured passes, and a part of the inner surface in a capacitance detection type electromagnetic flow meter detector. A detection electrode surface which is thinly fixed by metallization, a conductive portion which penetrates a part of the lining material and is formed up to the outer surface integrally with the lining material, an inner surface of these lining materials and the detection electrode surface. And an insulating coating material for covering the entire surface of the electromagnetic flowmeter thinly, and extracting a flow signal from the conductive portion.