WO2003065015A1 - Electromagnetic gravimeter - Google Patents

Abstract

Instead of a conventional means for transmitting a force acting on a float in a solution under test by means of the tension of a string, this electromagnetic gravimeter has a structure wherein a moving element (float) is electromagnetically coupled to a stator. The vertical position of the moving element is measured by utilizing a Hall device installed on the stator. The winding current of the stator is automatically controlled to generate an electromagnetic force so that the moving element always keeps the same position even when the gravity value of the solution under test changes. The gravity value of the solution is measured from this winding current value. A frictional force by the contact of the moving element with the stator is prevented by disposing the magnet magnetic circuit of the moving element and that of the stator in the direction of their repulsion.

Description

 Description Electromagnetic specific gravity meter Technical field

 The present invention relates to an electromagnetic hydrometer, which is used to measure the specific gravity of various solutions.

^ Background technology

 FIG. 1 is a configuration diagram of a conventional float-type hydrometer. 1 is a float, 2 is a thread, 3 is a hydrometer, and 4 is a solution to be measured. The buoyancy V acts on the float 1 according to its own gravity W and the product of its volume V and the specific gravity μ of the solution 4 to be measured, and the difference is transmitted to the yarn 2 as tension Τ. The hydrometer 3 converts the tension Τ into an electrical signal.

Many are practical, such as those that convert 10 mm into a displacement and electrically detect the displacement, or products that convert tension に into an electric signal by using a strain gauge or the like and convert it to the specific gravity of a solution. Has been

 However, due to the structure of the float type hydrometer, it cannot be installed in a place with a high flow velocity. Needed. In Fig. 1, 5 is a sampling tank and 6 is a perforated cover in the sampling tank, which minimizes the effect of flow velocity on the float. However, because the flow velocity was suppressed, the detection time was delayed due to a change in the liquid quality, and air bubbles adhered to the float 1, causing measurement errors. Also, the solution 4 was not suitable for applications in which toxic gas or corrosive gas was generated, and even if used, the hydrometer 3 had a short life. Furthermore, because of the open structure, it could not be installed on high-pressure piping.

For liquid hydrometers (densitometers) other than those shown in Fig. 1, see, for example, "Practical Industrial Analysis" (Yu Matsuyama, Energy Conservation Center, published on January 30, 2002, ISBN 4-87973-236-2). In addition to float type densitometers, differential pressure type densitometers, vibratory densitometers, etc. have been put into practical use. Disclosure of the invention

 The electromagnetic hydrometer of the present invention has a structure in which a mover (float) and a stator are magnetically coupled, and an electromagnetic force is generated in the mover (float) by energizing a coil on the stator side. Instead of transmitting the tension T by the thread of the conventional float-type hydrometer, an electromagnetic force F corresponding to the difference between the gravitational force W acting on the mover and the buoyancy is applied to the winding (coil) on the stator side. Detect as a value. The vertical position of the mover is detected using a Hall element or the like, and automatic control is performed so that the mover always maintains the same position even if the specific gravity of the solution to be measured fluctuates.

 Similarly, as a hydrometer using electromagnetic force, the inventions of Japanese Patent Publication No. 47-161 65 and Japanese Patent Publication No. 53-428 555 are known, each of which is movable. It is characterized by the method of supporting the child, that is, the means for maintaining the distance from the stator.

 In the former embodiment of the invention, a thin shaft is provided above and below the mover, and a disk having a hole in the center is provided above and below the stator side opposite to the mover. . However, because of the generation of frictional force due to the contact between the fitting parts, improvement in the measurement accuracy of the solution specific gravity cannot be expected. A differential transformer is described as an embodiment of the mover position detecting means.

In the latter embodiment, the mover and the stator each have a plurality of built-in magnets and are configured to repel each other, so that the mover is spatially held at a position where it does not contact the stator. Will be described. However, since the magnet has a pair of Ν and S poles, considering the distribution of lines of magnetic force, the mover is not spatially held, but is in an unstable equilibrium state. In other words, when the center is slightly deviated in the vertical or radial direction from the center, the mover is attracted in that direction by the magnetic force. In the vertical direction, the center position is maintained by controlling the coil current on the stator side. However, there is no means for controlling the mover position in the radial direction. An eddy current sensor is described as an embodiment of the mover position detecting means.

 In contrast to the above prior art, the magnetic circuit of the mover and the stator of the present invention has a cylindrical yoke (magnetic path iron portion), and this yoke constitutes a working surface where magnetic repulsion occurs. are doing.

5 Fig. 7 is a diagram showing the distribution of the lines of magnetic force in one embodiment of the present invention, where no attractive force acts in the radial direction and even if the mover and the stator partially contact during measurement. It has the characteristic that no frictional force is generated. BRIEF DESCRIPTION OF THE FIGURES

 Figure 1 shows a conventional float-type hydrometer and its installation in a sampling tank.

FIG. 2 is an external view of an electromagnetic hydrometer according to an embodiment of the present invention, which includes an electromagnetic conductivity meter and a liquid temperature sensor.

 FIG. 3 is a structural view of a mover and a stator according to an embodiment of the electromagnetic hydrometer according to the present invention. FIG. 4 is a block diagram of an electric circuit according to an embodiment of the electromagnetic hydrometer according to the present invention.

 FIG. 5 is another embodiment of the electromagnetic hydrometer according to the present invention, which is a simple structural diagram.

ig- Fig. 6 shows another embodiment of the electromagnetic hydrometer according to the present invention.

 FIG. 7 is a distribution diagram of magnetic lines of force in FIG. FIG. 8 shows another embodiment of the electromagnetic hydrometer according to the present invention, which is a simple structural diagram and a block diagram of an electric circuit. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 2 shows an embodiment of the electromagnetic hydrometer according to the present invention. Reference numeral 7 denotes a mover (float) having a donut-shaped through hole in a vertical direction, and a magnet magnetic circuit built in the peripheral surface of the through hole. Numeral 8 denotes a columnar stator, and a magnetic circuit, a winding (coil), and a mover position detecting means such as a Hall element are incorporated in a portion relative to the mover. 4 is the solution to be measured, 5 is It is a sampling tank. 9 is an electromagnetic conductivity meter, 10 is a liquid temperature sensor, and it is also possible to measure a plurality of characteristics of the solution with one sensor. Since no yarn is used to detect the buoyancy acting on the mover (float), it can be installed directly on piping or tanks with high flow rates. In addition, because it is easy to seal with outside air, it can be installed on high-pressure piping, as well as in applications that generate toxic and corrosive gases. FIG. 3 is an internal structure diagram of the mover Ί and the stator 8 in one embodiment of the electromagnetic hydrometer according to the present invention. 2 1 is the magnet of the mover, 2 2 is the yoke of the mover (magnetic iron part), 11 is the magnet of the stator, 12 is the yoke of the stator (magnetic iron part), and 13 is the stator There are 14 winding elements (coils) and 14 Hall elements, three on each of the N and S poles, for a total of six. 15 is an O-ring,, 16 is a stator case, 17 is a shaft, 18 is a spacer, 19 is a lower holder, 20 is an upper holder, and 23 is a mover case. Is also made of a non-magnetic material. 24 is an iron ring for preventing magnetic flux leakage to the surroundings.

 Of the cross-sectional views of the stator shown in FIG. 3, the figure above the center line is an embodiment in which the winding (coil) 13 is installed on the surface of the cylindrical yoke 12, and the figure below the center line of the stator is In this embodiment, a slot is provided in the yoke 12, and a winding (coil) 13 is provided in the slot.

Since the mover magnet 21 and the stator magnet 11 have the same polarity and are arranged to repel each other, no frictional force is generated even when the mover 7 and the stator 8 come into contact with each other. On the other hand, the current flowing through the stator coil 13 generates an electromagnetic force F by the product of the magnetic flux density of the mover magnet 21. By controlling the coil current so that the mover 7 maintains its vertical position, the buoyancy _μ ν acting on the mover 7 and, by extension, the specific gravity value of the solution to be measured are detected as a coil current.

In the cross-sectional view of the mover shown in Fig. 3, the figure on the left from the center line shows that the mover yoke 22 is chamfered near the magnet joint, and the mover magnet 21 is slightly separated from the stator. This is an example. In this embodiment, the stabilization of the mover position near the center point Is improved. FIG. 4 is an embodiment of an electric circuit used in the electromagnetic hydrometer of the present invention. 13 is a stator coil, 14 is a Hall element, 31 is a differential amplifier, 32 is an adder, 33 is a coil current detection resistor, and 34 is an amplifier. After adding the six Hall element voltages, the stator coil

5 Add the drop in Hall element voltage due to the current. The adjustment circuit 40 adjusts the offset voltage V off to obtain a voltage V _Z proportional to the position of the mover 7 in the vertical direction (Z direction). 3 5 is a V z differentiation circuit, which obtains the velocity signal of the mover.

 3 6 is a PID amplifier that controls the mover position signal V z constant, 3 7 is a PID amplifier that controls the mover speed, 3 8 is a PID amplifier that controls the stator coil current t0, and 3 9 is a fixed It is a current supply circuit to the child coils 13 and together constitutes a triple negative feedback closed loop. For example, the output of 36 is a speed command value, and the difference from the actual speed (dVz / dt) is input to 37. Similarly, the output of 37 is the coil current command value, and the difference from the actual current value is used as the input to 38.

 With the above configuration, the current is fixed so that the vertical position of the mover 7 is always kept constant.

\ 5 Supplied to child coil 13. By measuring the coil current value, the electromagnetic force F acting between the mover and the stator is measured, and the specific gravity of the solution to be measured is measured. FIG. 5 shows another embodiment of the electromagnetic hydrometer according to the present invention. With the mover 7 inside, the stator 8 was installed outside the sampling tank 5. 4 is the solution to be measured, and 11 and 22 are the same as in FIG.

 20 The mover 7, which is a donut-shaped float, has a magnet magnetic circuit (21,

2), which is opposed to the magnet magnetic circuit (1 1, 1 2) of the cylindrical stator 8. The stator 8 includes a coil 13 and a Hall element 14, and operates on the same principle as in FIG. 3, and also has the same electric circuit as in FIG. FIG. 6 shows another embodiment of the electromagnetic hydrometer according to the present invention. The stator 8 was divided into upper and lower parts, and the magnet 21 of the mover 7 which was a spindle-shaped float was also arranged in the upper and lower parts. 11 and 22 are the same as in FIG.

The magnet 21 of the mover 7 is cylindrical and magnetized in the radial direction. In other words, the upper mover magnet has all N poles on the outer circumference and the S pole on the inner circumference, and the lower mover magnet has all S poles on the outer circumference and N poles on the inner circumference. The upper and lower two mover magnets 21 are magnetically coupled through a yoke 22 inside the float. Two stator magnets 11 are arranged on the left and right sides of the pipe through which the solution to be measured flows. Both are N poles on the upper side and S poles on the lower side, and are arranged so as to repel the mover magnet 21. . The four long yokes 12 are formed in a cylindrical shape at positions opposed to the upper and lower magnets of the mover 7, and constitute the stator 8 together with the coil 13 and the Hall element 14. . The operating principle is the same as in Fig. 3, and the electrical circuit is the same as in Fig. 4. FIG. 8 shows another embodiment of the electric circuit used in the electromagnetic hydrometer according to the present invention. 11 to 18 are the same as in FIG. 3, and 31 to 40 are the same as in FIG. On both the N-pole side and the S-pole side, three Hall elements 14 are arranged above and below each other so as to sandwich the stator coil 13. The effect of the magnetomotive force of the coil current is offset by using the output difference between the Hall element voltages arranged above and below the stator coil 13 as the position signal V z of the mover. Since three Hall elements are arranged per circumference, there are a total of 12 Hall elements. 41 is a coil installed on the surface of the stator magnet to detect the speed of the mover. In other words, the amount of magnetic flux linking the coil 41 changes according to the position of the mover, and the time derivative of the generated voltage of the coil 41 is proportional to the speed (dVz / dt) of the mover. . The operating principles of 36 to 39 are the same as in FIG. Industrial applicability

 As described above, the electromagnetic hydrometer of the present invention does not use a thread for detecting the force acting on the mover (float), and thus can be directly installed on a pipe having a high flow velocity or in a tank. It is easily sealed from the outside air, and can be installed on high-pressure pipes as well as in applications that generate toxic or corrosive gases.

 In addition, as described in Fig. 2, by incorporating a hydrogen ion concentration (pH) meter, oxidation-reduction potential (ORP) meter, conductivity meter, liquid temperature sensor, etc. on the stator side, the solution can be Can be measured.

Claims

Scope of Claim Controlling the winding current so that gravity, buoyancy and electromagnetic force acting on the float in the solution to be measured are balanced, and measuring the specific gravity of the solution to be measured based on the winding current value. In an electromagnetic hydrometer,  It has a magnet magnetic circuit with a cylindrical yoke (magnetic path iron part) inside the mover, which is a float, and a cylindrical yoke (magnetic path iron part) on the side of the stator opposite to the mover. ), A winding for energizing to generate electromagnetic force in the vertical direction, and means for detecting the position of the mover in the vertical direction.  Both cylindrical yokes (magnetic path iron parts) have a nested structure in which the vertical axis is coaxial, and are configured to have the same magnetic polarity so that the radial direction between the mover and the stator can be reduced. An electromagnetic hydrometer that generates a repulsive force so that frictional force due to contact between the mover and stator does not act during measurement. The cylindrical yoke (magnetic path iron part) of the mover and stator has an L-shaped cross section along the vertical axis, which is magnetized together with a ring-shaped magnet magnetized in the vertical direction. The electromagnetic hydrometer according to claim 1, wherein the electromagnetic hydrometer comprises a circuit. At least one of a cylindrical magnet or a collective magnet magnetized in the radial direction is provided on each of the magnetic repulsive working surfaces of the cylindrical yoke (magnetic path iron portion) of the mover and the stator. 2. The electromagnetic gravimeter according to claim 1, wherein: