JPH032815Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an eddy current type current meter that measures the flow velocity of a conductive fluid to be measured based on eddy currents generated in the fluid to be measured.

FIG. 1 is a configuration explanatory diagram showing an example of a detection unit DET constituting the detection section of this type of device, in which CB is a coil bobbin, W _EX is an excitation coil wound around the coil bobbin CB, W _D1 , W _D2 is the excitation coil
This is a detection coil wound around a coil bobbin CB so as to sandwich W _EX .

The detection unit DET configured in this way is
Insert the coil bobbin CB into a guide tube (not shown) placed in the fluid so that the center axis of the coil bobbin CB matches the flow direction F of the conductive fluid to be measured.
When an alternating current signal is applied to W _EX , eddy currents are generated in this fluid. Note that depending on the fluid to be measured, the probe may be inserted directly into the fluid to be measured without being inserted into the guide tube. This eddy current is caused by the excitation coil W _EX
It can be roughly divided into two types: one is due to the magnetic flux φ caused by the magnetic flux φ, and the other is due to the electromotive force corresponding to the vector product of the magnetic flux φ and the flow velocity of the fluid. When the fluid moves at a certain flow velocity, the new magnetic flux generated by the latter eddy current mutually interferes with the main magnetic flux φ created by the exciting coil W _EX , and the magnetic flux distribution near the exciting coil W _EX occurs. is distorted from the shape shown by the second solid line φ to the shape shown by the dotted line φ'. Here, the amount Δφ by which the magnetic flux distribution is distorted corresponds to the flow velocity of the fluid to be measured. Signals e ₁ and e ₂ corresponding to the magnetic flux interlinked with the detection coils W _D1 and W _D2 are generated, and the amount of distortion in the magnetic flux distribution can be determined by calculating the difference between the two signals e ₁ and e ₂ . Δφ, that is, the flow velocity of the fluid to be measured can be determined.

By the way, conventionally, when connecting such a detection unit to an external circuit, a twisted wire TW is used for each coil, as shown in Fig. 3, and these twisted wires are connected in a flexible manner without being fixed to each other. The flexible tube FT is inserted into the guide tube WL, and the flexible tube FT is inserted into the guide tube WL.

However, with such a configuration, although the twisted wires can reduce electromagnetic induction noise to some extent, the positional relationship between the twisted wires may cause expansion or contraction of the constituent members due to temperature changes in the fluid to be measured, or the fluid flow of the fluid to be measured. It cannot be completely eliminated because it changes due to changes over time in the pressing force on the guide tube WL due to vibration.

The present invention solves these conventional drawbacks, and uses a core wire whose outer periphery is coated with a magnetic material as a lead wire to each coil of the detection section.
It is characterized by preventing electromagnetic induction noise from occurring in the lead wire.

Hereinafter, it will be explained in detail using the drawings.

FIG. 4 is a configuration explanatory diagram showing one embodiment of the present invention, and the same parts as in FIG. 3 are given the same reference numerals.

In FIG. 4, L is a pair of core wires, MS is a covering made of a magnetic material, ST is an outer sheath, and INS is an insulator. That is, in this embodiment, a pair of core wires L
The outer periphery of the sensor is coated with a coating MS made of a magnetic material (for example, iron, nickel, etc.) and is used as a lead wire to each coil of the detection section. In this embodiment, when storing a pair of core wires L in the covering MS, an insulating mineral is placed around the core wires L in order to prevent the positional relationship between the core wires L from changing. (for example, MnO ₂ , ZnO ₂ , Al ₂ O ₃ ). Further, a plurality of sheathing bodies MS in which the core wires L are housed in this manner are inserted into an outer sheathing ST made of stainless steel, for example, together with the same insulating mineral as described above, and the positional relationship between the sheathing bodies MS is changed. This prevents changes due to expansion or contraction of the constituent members due to changes in the temperature of the fluid to be measured, or changes over time in the pressing force against the guide tube WL due to fluid vibrations of the fluid to be measured.

According to such a configuration, since the outer periphery of the core wire L is covered with the covering MS made of a magnetic material, it is possible to extremely reduce the generation of electromagnetic induction noise in the lead wire as in the conventional case. Furthermore, even if electromagnetic induction noise were to occur, the positional relationships between the core wires L and between the coverings MS would not change significantly as in the past, and the change in electromagnetic induction noise would be sufficiently small. Residual electromagnetic induction noise can be removed by electrical circuit processing, resulting in high resolution.

In the above embodiment, a pair of core wires are housed in a cover made of a magnetic material, but one core wire or three or more core wires may be housed depending on the application.

Furthermore, in order to fix the positional relationship between the coverings, brazing, adhesive, fixing member, etc. may be used between the coverings.

In addition, if there is a risk that the covering may oxidize, an inert gas may be filled inside the covering and the outer covering.

As explained above, according to the present invention, it is possible to realize an eddy current current meter that generates less electromagnetic induction noise and has high measurement resolution, and is suitable for measuring the flow velocity and flow rate of conductive fluids to be measured such as liquid sodium. suitable.

[Brief explanation of the drawing]

Fig. 1 is a configuration explanatory diagram showing an example of the detection unit DET that constitutes the detection section of this type of device, Fig. 2 is an explanatory diagram of the operation of Fig. 1, and Fig. 3 shows an example of the conventional lead wire structure. FIG. 4 is an explanatory diagram showing an example of a lead wire structure according to the present invention. L...Core wire, MS...Coating (magnetic material), ST...
...Sheath, INS...Insulating mineral.

Claims (1)

[Scope of utility model registration request] Using a detection section that includes an excitation coil to which an alternating current signal is applied along the flow direction of the conductive fluid to be measured and at least two detection coils arranged near the excitation coil, any two detection coils can be used. In an eddy current current meter configured to determine the flow velocity of the fluid to be measured based on the difference between the output signals of An eddy current type current meter characterized by using.