JPS63145933A - Electric measurement - Google Patents

Abstract

PURPOSE:To measure quantity to be measured by means of a simple construction, by arranging primary windings near shape-changed parts of a magnetic fluid in a container to detect changes in the shape of the magnetic fluid in the container depending on changes in an electromotive force induced in secondary windings. CONSTITUTION:A magnetic fluid 2 is put into a U-shaped communicating tube 1 and primary windings P and P' are arranged near a reference fluid face of both the rises thereof while secondary windings S and S' at the end of the communicating tube 1 side by side along the axis lines of the primary windings P and P'. AC current flows through the primary windings P and P' and a differential potential is detected between an induced electromotive force generated in the secondary winding S and that generated in the secondary winding S' both by a magnetic flux generated. This enables electrical measurement of pressure as quantity to be measured by means of a handy construction.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to measurement target quantities, particularly inclination, acceleration, rotational speed,
Related to electrical measurement methods such as differential pressure, pressure, liquid level, flow rate, etc.

[Conventional technology]

Communication pipes, such as 0-shaped pipes, have been widely used since ancient times as basic measuring instruments for differential pressure, pressure, liquid level, flow rate, and the like.

Conventionally, in order to convert the difference in the height of the fluid surface between the two legs into an electrical signal, a float is floated on the fluid surface, and the displacement of the float is transmitted to the outside of the tube via a rank and pinion mechanism and a magnetic coupling device. There is a method of converting the rotational displacement into an electrical signal using some suitable rotational displacement-electrical signal converter, or floating a float made of iron on the fluid surface and converting the displacement to the outside of the pipe by electromagnetic induction. Electrical detection methods have been adopted.

Due to horizontal acceleration, the surface of the fluid in the container is expressed by the following equation (1
), but it has not been easy to convert this slope into an electrical signal.

It is well known that the fluid in a cylindrical container becomes a paraboloid of rotation according to equations (2) and (3) below due to rotation around the vertical axis of the container. However, converting it into an electrical signal has not been easy in the past. For this purpose, it was previously necessary to manually read the height of the rise of the paraboloid of revolution. When measuring differential pressure using a differential pressure measurement cell using a diaphragm, it is necessary to manually measure the height of the rise of the paraboloid of revolution. Methods that have been adopted include converting it into a change in electrical resistance using a gauge, and converting it into a change in differential capacitance between a (movable) electrode attached to a measuring diaphragm and a fixed electrode facing it. The electrical signals obtained by these methods are minute, and it would be advantageous if larger electrical signals could be obtained directly.

The development of applications for magnetic fluids has focused on bearing seals, metal flotation sorting, vibration dampers, etc., and the development of measurement methods that take advantage of the ability of magnetic fluids to change shape freely has only just begun. It is a stage.

[Problem that the invention seeks to solve]

The object of the present invention is to provide an electrical measuring method for inclination, acceleration, rotational speed, differential pressure, pressure, liquid level, flow rate, etc., which has a simple structure and circuit, has a large output voltage, and can be used in the future. The object of the present invention is to make it possible to realize a measuring device that is easy to process and has excellent economical efficiency.

[Means for solving problems]

According to the present invention, the purpose of this is to detect the shape change of the magnetic fluid in the container due to the quantity to be measured from the primary winding, which is arranged near the shape changing part of the magnetic fluid and is excited by alternating current. By detecting changes in the electromotive force induced in the secondary winding placed near the winding,
This is achieved by measuring the quantity to be measured.

Preferred embodiments of the invention are set out in claims 2 to 19.

〔Effect of the invention〕

According to the electrical measuring method of the present invention, a measuring device having features such as a simple structure and circuit, a large output voltage (therefore, subsequent processing is easy, and is excellent in economical efficiency) can be obtained. can get.

〔Example〕

The invention will be explained in more detail below by means of embodiments shown in the drawings. Corresponding elements are provided with the same reference symbols throughout the drawings.

A magnetic fluid has a lower magnetic permeability than an iron core, but has the characteristic of being free to change shape. A small magnetic permeability reduces the sensitivity of detecting mechanical quantities as explained below, but according to the applicant's experiments, the sensitivity when using a magnetic fluid is at least as high as the sensitivity when using an iron core. It is 17% and does not cause any trouble in subsequent processing. Note that magnetic fluid does not produce hysteresis, and eddy currents
According to the applicant's experiments, this also has the characteristic that it does not pose a problem.

Some of the embodiments described below differ fundamentally from previously known differential transformers in that the magnetic fluid corresponding to the core extends beyond one end of the winding. Figure 1 shows the tip position of the magnetic fluid and the induced induction of the secondary winding when the secondary windings are arranged in the axial direction on both sides of the primary winding (hereinafter referred to as a three-stage type). It is a graph showing the relationship between power and electric power. V, indicates the induced electromotive force in the left secondary winding in Figure 1, vs' indicates the induced electromotive force in the right secondary winding in Figure 1, and Vs() is the difference between VS and VS'. It shows the difference voltage, and Vs (+) shows the sum voltage of V, y, and J. Figure 2 also shows the tip position of the magnetic fluid and the induced effect of the secondary winding when the secondary winding is arranged radially overlapping the primary winding (hereinafter referred to as a two-stage type). It is a graph showing the relationship between power and electric power. vs is second
In the figure, the induced electromotive force of the left secondary winding is shown, and v and l are the second
The figure shows the induced electromotive force in the secondary winding on the right, and Vs() is V
, and vs'. From Figure 1 for the 3-stage type, it is clear that when using the difference between the induced electromotive forces of two secondary windings, the range is monotonous, compared to when using the induced electromotive force of one secondary winding. is slightly narrower, but linearity is improved and the base is smaller (larger maximum/minimum ratio)
It can be seen that this is advantageous in some respects. In addition, when using the sum of the induced electromotive forces of two secondary windings, the monotonous range becomes wider and the linearity is also lower than when using the induced electromotive force of one secondary winding. Although this is improved, the base component is large, which is the same as when using the induced electromotive force of one secondary winding. 2 yen for 3 tiers! When compared with the JT type, it can be seen that the three-stage type has a wider range of linearity, but the slope of the characteristic curve is gentler, that is, the sensitivity is lower. (In addition,
As can be seen from Figure 10 below, the rate at which the magnetic flux generated by the primary winding effectively interlinks with the secondary winding is approximately 1/3 in the three-stage type compared to the two-stage type. In terms of sensitivity when the excitation ampere turns of the primary winding are the same, it can be said that the two-stage type is far superior to the three-stage type. ) Next, as a first embodiment of the present invention, a communication pipe, for example 0
A case will be described in which the difference in fluid levels between the two legs of the tube is detected. In this case, it is advantageous for the cross-sectional areas of the tubes in the detection areas of both legs to be substantially equal.

In other words, in this case, the decrease in the fluid level in one leg is equal to the increase in the fluid level in the other leg, so it is possible to detect only the fluid level in either leg, or it is possible to detect the fluid level in both legs. In the case of detection, it is sufficient to provide similarly designed detection means on both legs.

In a preferred embodiment of the invention, detection is performed on both legs, as shown in FIG. A magnetic fluid 2 is contained in a U-shaped communication tube 1, and one primary winding P, P' is arranged in the vicinity of a reference fluid level on both legs of the magnetic fluid 2. Secondary windings s and s' are arranged on the end side of the communication pipe l, axially aligned with the primary windings P and P'. Primary winding P,
The difference VS (-) between the induced electromotive force generated in the secondary winding S and the induced electromotive force generated in the secondary winding S' by the magnetic flux generated by flowing an alternating current through P' is detected. The reason for performing detection in both legs is, firstly, that a linear relationship is obtained between the displacement of the fluid surface and the induced electromotive force in the secondary winding, as shown in FIG. Second, even if the reference fluid level changes due to the influence of outside air temperature, it can be made almost unaffected. According to actual measurements by the applicant, the magnetic fluid has a magnetic flux of about Q, 065%/d e g
For example, if the length of the magnetic fluid is lQcm and the outside temperature changes by 50°C, the reference fluid level changes by 3.25 mm. As shown in the experimental results in Figure 5, by performing detection with both legs, it was confirmed that there is a range in which the measurement results are hardly affected even if there is a change of this degree in the reference fluid level. . this is,
This is possible by utilizing a range in which the relationship between the fluid level and the induced electromotive force in each leg is linear.

In the embodiment shown in FIG. 3, one secondary winding is disposed on each leg, but one secondary winding is disposed on each leg axially on both sides of the primary winding. It is also possible to detect the difference between the induced electromotive force difference between the secondary windings on both sides in one leg and the induced electromotive force difference between the secondary windings on both sides in the other leg. Alternatively, it is also possible to detect the difference between the sum of the induced emfs of both secondary windings in one leg and the sum of the induced emfs of both secondary windings in the other leg.

The difference in fluid level between the two legs of the communicating tube is caused firstly by the difference in pressure applied to the two legs (FIG. 6(a)). Second, if the pressure in one leg is kept constant, it is caused by the pressure applied to the other leg (Figure 6(b)). Thirdly, if the pressure of one leg is maintained at the reference pressure and the other leg is connected near the bottom of the container containing the fluid whose liquid level is to be measured, the Figure 6(C)). Fourthly, if the pressure difference on both sides of the throttle mechanism is applied to both legs, it will occur in relation to the flow rate of the fluid passing through the throttle mechanism (Figure 6(d)).Fifth, the communicating pipe is inclined. if,
This occurs depending on the angle of inclination (Fig. 6(e)). Sixth, if the communication pipe is subjected to acceleration in the horizontal direction, as shown in Fig. 6 (
As shown in f), a difference occurs in the fluid levels between the two legs according to equation (1) below.

Connecting the opening of the communication tube on the side opposite to the magnetic fluid with a connecting tube as shown in FIG. 7 is advantageous in that effects such as evaporation of the magnetic fluid can be avoided.

In this case, by providing the throttle mechanism 3 in the connecting pipe, the dynamic characteristics can be made into desired characteristics.

FIG. 8 shows an example in which the inclination of the fluid surface of the magnetic fluid 2 in one container 5 is measured.

Here, the inclination of the fluid surface of the magnetic fluid may be due to the inclination of the container, or may be due to the acceleration of the container in the horizontal direction (leftward in FIG. 8).
(1) Here, a may be generated according to horizontal acceleration, and g may be generated according to gravitational acceleration. A primary winding P is arranged near the reference fluid level. Secondary windings S and S' are arranged radially overlapping the primary winding P and adjacent to each other in the axial direction. The difference between the induced electromotive force of the secondary winding S and the induced electromotive force of the secondary winding S' is detected. FIG. 9 shows actual measurement results of the relationship between the inclination angle of the fluid surface of the magnetic fluid and the induced electromotive force of the secondary winding. The reason why the secondary winding is arranged radially overlapping the primary winding is to keep the primary winding far enough away from the secondary winding that the magnetic fluid is contained in the primary winding. When placed downward, the rate at which the magnetic flux from the primary winding interlinks with the secondary winding is shown in Figure 10 (the horizontal axis is the distance d between the axial centers of the two windings and the mutually equal axial direction of the two windings). This is a significant decrease as shown in the ratio to length D). Having the magnetic fluid always in the primary winding is advantageous in terms of linearity between the position of the fluid surface and the induced electromotive force when the fluid surface of the magnetic fluid is perpendicular to its axis. However, in this case, it is difficult to achieve this, so the secondary winding is connected to the primary winding so that as much magnetic flux from the primary winding as possible interlinks with the secondary winding. They were placed one on top of the other in the radial direction.

When detecting the inclination of the fluid level in a container, it must be taken into account that the position of the reference (non-inclined) fluid level changes depending on the outside temperature and the like. FIG. 11 shows the results of actually measuring the relationship between the position of the reference fluid level and the induced electromotive force using the inclination angle as a parameter. As you can see from this diagram,
There are regions where the induced electromotive force changes monotonically (almost linearly or at least slightly non-linearly) depending on the position of the reference fluid level, and there are also areas where the induced electromotive force does not change much depending on the position of the reference fluid level. It has been confirmed that it exists. If the change in the reference fluid level is due to a change in the outside temperature and is compensated for by a compensation circuit that combines a manganin wire resistance and a copper wire resistance, for example, it is advantageous to use the former region; If such compensation is not performed, it is advantageous to use the latter region where the change is small.

Figure 12 shows the characteristics of Figure 9 as horizontal acceleration a using equation (1).
(ratio to gravitational acceleration g) and induced electromotive force. In this figure, it can be seen that when the horizontal acceleration is small, the sensitivity is low. It is easy to linearize nonlinearity using, for example, a broken line function circuit. However, if it is desired to measure low accelerations with high sensitivity, it is also possible to use a method using a communicating tube as shown in FIG. 6<r>.

In the structure example shown in FIG. 9, in order to make the structure compact, the length of the cylindrical container 5 is selected to be equal to the length of the primary winding P, and when the fluid surface is inclined at approximately 51 degrees, , until the top and bottom of the fluid touch the top and bottom of the container 5. As an alternative construction, it is also possible to use a container that is sufficiently longer than the length of the primary winding P.

FIG. 13 shows an embodiment for measuring the rotational speed about a vertical axis. It is known that when a cylinder rotates around its axis, the fluid enclosed within the cylinder becomes a paraboloid of revolution as shown in Figure 14 and equation (2) or equation (3). .

h= (ycrn/60) 2/g (
2) H-(n ・2yrr/60) ・(hc/2
g) l72 Here, h is the distance from the static fluid level to the highest and lowest fluid levels (Fig. 14 (a)), r is the radius of the cylinder, n is the rotational speed (rpm), g is the gravitational acceleration,
hc is h when the highest fluid level is just in contact with the top surface of the container
(Figure 14 (b)'), H is the distance from the highest fluid level to the lowest fluid level after the highest fluid level touches the top surface of the container (Figure 14 (C)). In a cylinder, when the rotation speed exceeds a certain number, the bottom of the concave reaches the bottom of the cylinder, so in that case, the volume of the magnetic fluid that would be concave if it did not reach the bottom of the cylinder is inside the paraboloid of rotation. Calculated by approximating that attached to . FIG. 15 illustrates the results of this calculation. The placement of the secondary winding radially outwardly with respect to the primary winding in FIG. 13 is for the same reason as previously discussed in connection with FIG. As in the case of Figures 8 and 9,
The difference between the induced electromotive force of the secondary winding S and the induced electromotive force of the secondary winding S' is detected. FIG. 16 shows the characteristics when the winding positions are varied. In this figure, the position of the winding is
It is indicated by the distance of the center of the primary winding upward from the horizontal fluid level when the rotational speed is O. As can be seen from FIG. 16(a), above a certain number of rotations, there is a range in which the change in characteristics due to the position of the reference fluid level is small. By arranging the winding at such a position, the influence of changes in the reference fluid level due to changes in outside air temperature can be minimized. Further, depending on the selection of the position of the winding, as shown in FIG. 16(b), a characteristic in which the induced electromotive force changes stepwise after a certain number of revolutions is obtained can be obtained. Such characteristics are useful as rotational speed switches or centrifugal force switches.

FIG. 17 shows an outline of an apparatus for measuring pressure differences and the like using a diaphragm type measurement cell filled with magnetic fluid. A cell 9 is formed by a floating diaphragm 8 in a body 7 having pressure receiving diaphragms 6,6' on both sides.
is retained.

The cell 9 includes an electrically insulating body 10 having a hollow part and a hole connecting the hollow part to both side surfaces;
A measuring diaphragm 11 stretched in the center of the measuring diaphragm 11, a thin film primary winding 12 attached to the measuring diaphragm 11,
A thin film-like secondary winding 13.13' attached to both inner surfaces of the electrically insulating body 10, facing the primary winding 12.
and has. The space on both sides of the measuring diaphragm 11 surrounded by the pressure-receiving diaphragm 6 , 6 ′, the body 7 , the floating diaphragm 8 and the cell 9 is filled with magnetic fluid 2 . Depending on the pressure difference, the pressure-receiving diaphragm 6.6' deflects and thus also changes the shape of the magnetic fluid. From a thin-film primary winding 12 fixed to the measuring diaphragm 11, which deflects as the magnetic fluid changes shape, to a thin-film secondary winding 13, 13' fixed to the electrically insulating body 10. By detecting changes in the electromotive force induced in the diaphragms 6, 6', it is possible to measure the difference in pressure applied to the pressure receiving diaphragms 6,6' on both sides. FIG. 18 is an example in which one side is set to atmospheric pressure and the relationship between the pressure applied to the other side and the induced electromotive force is actually measured. It goes without saying that this pressure difference measuring method can also be applied to measuring pressure, liquid level, and flow rate, as in the case of communicating pipes.

Although the present invention has been described above with reference to some preferred embodiments, it is understood that the present invention is not limited to these embodiments, and that various embodiments are possible within the scope of the present invention. This will be obvious to businesses.

[Brief explanation of the drawing]

Figure 1 shows the distance between the tip position of the magnetic fluid and the induced electromotive force of the secondary winding when the secondary windings are arranged in the axial direction on both sides of the primary winding (three-stage type). Figure 2 is a graph showing the relationship between the tip position of the magnetic fluid and the induction of the secondary winding when the secondary winding is arranged radially overlapping the primary winding (two-stage type). A graph showing the relationship between the electromotive force and the electromotive force. FIG. 3 is a schematic diagram of an example of measuring the difference in fluid level height between both legs of a communicating tube. FIG. 4 is a graph showing the relationship between the two legs of a communicating tube. Figure 5 is a graph showing the relationship between the height difference between the fluid levels of both legs and the induced electromotive force of the secondary winding. FIG. 6 is a graph showing the relationship between position and induced electromotive force; FIG. 6 is a schematic diagram showing an application example of measuring various quantities through the measurement of the height difference between the fluid levels of the two legs of a communicating tube; FIG. The figures are a schematic diagram of a modified example of the embodiment shown in Figure 3, Figure 8 is a schematic diagram of an embodiment for measuring the inclination of the fluid surface of a magnetic fluid in one container, and Figure 9
The figure is a graph showing the relationship between the inclination angle and the induced electromotive force of the secondary winding in the embodiment shown in Figure 8, and Figure 10 is a graph showing the relationship between the magnetic flux from the primary winding and the secondary winding and the relationship between the primary and secondary windings. FIG. 11 is a graph showing the relationship between the distance between the winding and the secondary winding, FIG. 11 is a graph showing the relationship between the position of the reference fluid level and the induced electromotive force using the inclination angle as a parameter, and FIG. A graph converting the characteristics in Figure 9 into the relationship between horizontal acceleration and induced electromotive force,
Fig. 13 is a schematic diagram of an embodiment for measuring rotational speed around a vertical axis, Fig. 14 is a diagram for explaining the shape of a fluid in a rotating cylinder, and Fig. 15 is an implementation of Fig. 13. FIG. 16 is a graph showing the relationship between rotational speed and induced electromotive force when the winding position is variously changed. FIG. 17 is a graph showing the shape of the fluid in the rotating cylinder in the example. FIG. 18 is a graph showing the relationship between pressure and induced electromotive force in the embodiment of FIG. 17. DESCRIPTION OF SYMBOLS 1...Communication pipe, 2...Magnetic fluid, 3...Adjustment orifice, 5...Cylindrical container, 6.6'...Pressure receiving diaphragm, 7...Body, 8...Floating diaphragm , 9... Cell, 10... Electrically insulating body, 11
... Measuring diaphragm, 12... Primary winding, 13.
13'...Secondary winding, P, P'...Primary winding, s,
s'... Secondary winding patent applicant Akira Ishibashi - Yuji Kanzaki Mitsuo Naito t + ngii force Vm + Vs' (arVIIJ48 power V ++l (Ml u4am force v, (-1F) 11 pigeon 4 electromotive force V =, v, '[mVl ljlil electromotive force V+ +-1I9] Fig. 4 - 404nm 14 position) Patent applicant: Ishibashi Yuji, Kanzaki Yuji, Uchiyoshi Mitsuo,
i15 Fig. 6 Fig. 7 Second position cdIO] Fig. 10 "1IlIJl Oblique angle θ (d e g) Fig. 9-4-21) 2 4mm (Tobj position l NI II! ! Al2g Figure 13 (σ1.JJ(bl fcl Figure 14 m rotation number 1reml
11 turns + rpm (ml
(b) 1st gIII pressure (kgrl Fig. 18

Claims (1)

[Claims] 1) In a method for electrically measuring a quantity to be measured, the change in shape of a magnetic fluid in a container due to the quantity to be measured can be detected by disposing the magnetic fluid in the vicinity of a shape-changing portion of the magnetic fluid. The quantity to be measured is measured by detecting a change in electromotive force induced from a primary winding excited by alternating current to a secondary winding arranged near the primary winding. Electrical measurement method. 2) In order to measure the difference in pressure applied to the fluid surface of both legs of a communicating tube, for example, a U-shaped tube, the difference in the height of the fluid surface of the magnetic fluid in both legs of the communicating tube due to the pressure difference is calculated using the magnetic By detecting changes in electromotive force induced from a primary winding located near the fluid surface of the fluid and excited by alternating current to a secondary winding located near the primary winding, The electrical measuring method according to claim 1, characterized in that a pressure difference is measured. 3) The electrical system according to claim 2, characterized in that a primary winding and a secondary winding are arranged on both legs of the communicating pipe, and the difference in induced electromotive force of each secondary winding is detected. Measuring method. 4) The electrical measurement method according to claim 3, wherein the cross-sectional areas of the detection regions of both legs of the communicating tube are substantially equal. 5) Arranging one secondary winding on each side of the axial center of one primary winding, spaced apart from each other, and detecting the difference or sum of the induced electromotive force of these two secondary windings. An electrical measuring method according to claim 2 or 3, characterized in that: 6) arranging two secondary windings radially overlapping and axially aligned with each other with respect to one primary winding,
The electrical measuring method according to claim 2 or 3, characterized in that the difference in induced electromotive force between these two secondary windings is detected. 7) The electrical measurement method according to claim 2, characterized in that the opening of the communication tube on the opposite side to the magnetic fluid is connected by a connecting tube. 8) The electrical measurement method according to claim 7, wherein the connecting pipe is provided with a throttle mechanism. 9) The method according to any one of claims 2 to 8, characterized in that the pressure in one leg of the communicating pipe is maintained at a reference pressure, and the pressure applied to the other leg is measured. Electrical measurement method. 10) The pressure in one leg of the communication pipe is maintained at a reference pressure, and the liquid level in the container connected to the other leg is measured. The electrical measurement method according to any one of the items. 11) The electricity according to any one of claims 2 to 8, characterized in that the flow rate of fluid passing through the throttle mechanism is measured by measuring the pressure difference on both sides of the throttle mechanism. measurement method. 12) The electrical measuring method according to any one of claims 2 to 8, characterized in that an inclination angle is measured. 13) The electrical measurement method according to any one of claims 2 to 8, characterized in that acceleration in the horizontal direction is measured. 14) To measure the horizontal acceleration, the slope of the fluid surface of the magnetic fluid in the container is measured from the primary winding, which is placed near the fluid surface of the magnetic fluid and is excited by an alternating current, to the primary winding. 2. The electrical measurement method according to claim 1, wherein horizontal acceleration is measured by detecting changes in electromotive force induced in a secondary winding placed nearby. 15) To measure the rotational speed, we measure the change in the paraboloid of revolution shape of the fluid surface of the magnetic fluid in the container due to the rotational speed.
Detection based on changes in electromotive force induced from a primary winding located near the fluid surface of the magnetic fluid and excited by alternating current to a secondary winding located near the primary winding. 2. The electrical measuring method according to claim 1, wherein the rotational speed is measured by: 16) In order to measure the pressure difference, a magnetic fluid is sealed in a body having pressure receiving diaphragms on both sides separated by a measuring diaphragm, and the deflection of the pressure receiving diaphragm according to the pressure difference, and therefore also A secondary winding disposed near the primary winding on the body side is configured to detect the shape change of the magnetic fluid from a primary winding fixed to the measuring diaphragm that deviates with the shape change of the magnetic fluid. 2. The electrical measurement method according to claim 1, wherein the difference in pressure applied to both pressure receiving diaphragms is measured by detecting a change in electromotive force induced in the pressure receiving diaphragm. 17) The electrical measuring method according to claim 16, characterized in that the pressure of one pressure receiving diaphragm is maintained at a reference pressure and the pressure applied to the other pressure receiving diaphragm is measured. 18) Claim 16 characterized in that the pressure of one of the pressure receiving diaphragms is maintained at a reference pressure and the liquid level in the container connected to the other pressure receiving diaphragm is measured.
Electrical measurement method described in section. 19) The electrical measuring method according to claim 16, characterized in that the flow rate of fluid passing through the throttle mechanism is measured by measuring the pressure difference on both sides of the throttle mechanism.