JP3328733B2 - Weight measuring method, weight measuring device and cylindrical electromagnetic induction sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the weight of a part made of a magnetic metal or other magnetic material by measuring the electromotive force generated by the law of electromagnetic induction, and multiplying the numerical value of the output voltage by a weight conversion coefficient. A new non-contact weight measurement method that does not use gravity, a weight measurement device for it, and a cylindrical electromagnetic induction sensor therefor that automatically and speedily measures the weight by calculating the weight. Is provided.

[0002]

2. Description of the Related Art Various methods have been developed for measuring the weight and mass of raw materials, parts, products, and the like. Since the mass cannot be directly measured, the weight based on the acceleration of gravity, that is, gravity is used to measure the weight directly or through leverage with the known gravity acting on the mass. As the counterweight, the elastic force of a spring, the restoring force of a pendulum, buoyancy, pressure, and the like are used, and a wide variety of instruments according to the purpose have been developed. Recently, electronic scales and load cells have been developed with high measurement accuracy, and the measurement accuracy can be measured down to 0.001 g. However, it takes 7 seconds / piece for measuring time to stabilize the measured value at the time of measurement, and it is weak against the vibration of the working environment, and there are technical problems such as difficulty in transporting the measuring instrument due to the shape. In many cases, it has been difficult at present to incorporate automation and labor saving in the manufacturing industry. Therefore, in the factory weight inspection, in many cases, several sampling inspection methods are manually performed for each predetermined rod. The technical problem described above is an unavoidable technical barrier as long as a gravity measurement method using gravity is adopted.

[0003]

Accordingly, the present inventors have developed a new weight measuring method and apparatus suitable for automation, labor saving, and speeding up which are strongly demanded from various fields. I decided to work on it. After diligent research, he realized that there is a possibility of measuring weight using the eddy current and the law of electromagnetic induction, and decided to work on development. According to the results of the investigation, many inspection devices have been developed in various fields, such as composition differences, dimensional differences, and flaw detection, using eddy currents and the law of electromagnetic induction. There was no place.

[0004] The inventors of the present invention induced electromagnetic induction according to the operation principle as shown in FIG. 1, and examined what could be sensed by measuring the generated electromotive force, and studied whether the weight could not be measured. . It comprises two coils 1 and 2 arranged concentrically on a coil bobbin 3 with an electromagnet coil 1 for creating a magnetic field in the coil body on the outside and a coil cylinder on the inside. An electromagnetic induction coil 2 for inducing an electromotive force by a change in a magnetic field A generated in the body. The electromagnetic induction coil 2 is configured so that a test material 4 can pass through the inside of the coil cylinder. The instrument which measures is connected. That is, a cylindrical type in which the magnetic flux generated by the electromagnet coil 1 is formed so as to penetrate through the electromagnetic induction coil 2, and an electromotive force is generated in the electromagnetic induction coil 2 by changing the magnetic field in the electromagnetic induction coil 2. It is an electromagnetic induction sensor. When a prototype of the cylindrical electromagnetic induction sensor was built and subjected to various tests, it was found that the operation was as follows.

When an alternating current is applied to the electromagnet coil 1, a magnetic field A is generated. When the test material 4 is passed through the coil cylinder, its magnetic field A changes (due to a change in magnetic flux or the generation of an eddy current in the test material). When the magnetic field A changes, an induced electromotive force is generated and changed in the electromagnetic induction coil 2 according to the law of electromagnetic induction. The voltage of the electromagnetic induction coil 2 changes in proportion to the volume (weight) of the sample.

In particular, the technical finding that "the voltage of the electromagnetic induction coil changes in proportion to the volume (weight) of the test material" is a finding newly found by the present inventors from many test data. By using this, it is possible to measure the weight. Then, based on this new knowledge, the inventors shall develop a new weighing method and weighing device, and set the target value of the weighing accuracy to ± 40 g of the measured weight.
Ensure repeatability of 0.5g. The measurement speed was determined to secure a workpiece feeding speed of 0.5 seconds / piece.

[0007]

Means for Solving the Problems The present invention is constituted as follows as means for achieving the above object.

In the first invention to be patented, the magnetic field is changed by passing the magnetic material to be measured through the magnetic field along the direction of the magnetic field, thereby generating an electromotive force in the electromagnetic induction coil, A weight measuring method characterized in that an output voltage of the induced electromotive force is measured, and a weight is calculated by multiplying a numerical value of the digitized output voltage by a weight conversion coefficient.

This is an invention of a basic weight measuring method utilizing the above technical knowledge that the voltage of the electromagnetic induction coil changes in proportion to the volume (weight) of the sample. The peak value of the output voltage of the induced electromotive force is specified as a measured value, converted to a digital signal by an analog-to-digital converter, and the weight is calculated by multiplying the numerical value of the output voltage by a weight conversion coefficient. is there. The weight conversion coefficient is set in advance so that the weight can be calculated from the numerical value of the output voltage using a sample serving as a model.

The weight measuring method according to the present invention is characterized in that it is not affected by the working environment because it is a non-contact measurement, and that it can be transported at a high speed for measurement while the sample is moving.

According to a second aspect of the invention, a cylindrical electromagnetic induction sensor is provided which is formed so that a magnetic flux generated by the electromagnetic coil passes through the electromagnetic induction coil, and a current flows through the electromagnetic coil. By generating a magnetic field in the cylinder of the cylindrical electromagnetic induction sensor, by passing the magnetic material to be measured at a predetermined speed through the cylinder of the cylindrical electromagnetic induction sensor, the magnetic field in the cylinder is changed. An electromotive force is generated in the electromagnetic induction coil, the peak value of the output voltage of the induced electromotive force is measured, converted into a numerical value by analog / digital conversion means, and the output voltage value is multiplied by a weight conversion coefficient by the calculating means. A weight measuring method characterized in that a weight is calculated by using a weight.

This is a method for measuring the weight of a magnetic material to be measured using a newly developed cylindrical electromagnetic induction sensor. As in the first invention, the weight measurement method according to the present invention is also non-contact measurement, so it is not affected by the working environment, and can be transported at high speed for measurement during sample movement. This is a suitable weight measurement method. In addition, a cylindrical electromagnetic induction sensor can generate a magnetic field at a predetermined strength within the coil at any time by passing an alternating current to the electromagnet coil, so that it is easy to handle and has a high practical weight for industrial use. It is a measuring method.

According to a third aspect of the present invention, there is provided a weight measuring apparatus comprising a cylindrical electromagnetic induction sensor, a magnetic material conveying means to be measured, a voltage measuring means, a calculating means, and a display means. It is.

The cylindrical electromagnetic induction sensor comprises an electromagnetic coil and an electromagnetic induction coil, and is arranged and formed so that a magnetic flux generated by the electromagnetic coil passes through the electromagnetic induction coil, and changes a magnetic field in the electromagnetic induction coil. Thus, an electromotive force is generated in the electromagnetic induction coil. For example, the cylindrical electromagnetic induction sensors according to the fourth and fifth inventions are sufficient.

Further, the magnetic material to be measured transport means is disposed so as to penetrate through the cylinder of the cylindrical electromagnetic induction sensor, and is configured to pass the magnetic material to be measured supplied from the supply means at a predetermined speed. It is made. Various conveyance means such as a belt conveyor and a sliding movement guide are conceivable,
It is sufficient if the magnetic field is not changed or a constant magnetic field change is always performed and can be corrected.

The voltage measuring means is connected to the electromagnetic induction coil of the cylindrical electromagnetic induction sensor, measures the output voltage of the electromotive force generated in the electromagnetic induction coil by a change in the magnetic field, and measures the output voltage of the induced electromotive force. This is a means for selecting a peak value and digitizing it by analog-digital conversion means.

The calculating means is means for calculating the weight by multiplying the numerical value of the measured output voltage by a predetermined weight conversion coefficient. A personal computer or the like is optimal as the calculation means.

The display means is a means for displaying the measured and calculated weight value as it is, for displaying an evaluation judgment by comparing a predetermined standard weight with the weight value, or for displaying both of them. .

According to a fourth aspect of the present invention, an electromagnet coil and an electromagnetic induction coil are arranged concentrically so that the magnetic flux generated by the internal electromagnet coil passes through the electromagnetic induction coil. By generating a magnetic field in the cylinder of the cylindrical electromagnetic induction sensor by applying a current to the electromagnet coil, by passing the magnetic material to be measured at a predetermined speed in the cylinder of the cylindrical electromagnetic induction sensor, A cylindrical electromagnetic induction sensor characterized in that an electromotive force is generated in an electromagnetic induction coil by changing a magnetic field in a cylinder. In general, the electromagnet coil is disposed outside and the electromagnetic induction coil is disposed inside, but it is a matter of course that the electromagnetic coil may be disposed in reverse if necessary.

In a fifth aspect of the invention, an electromagnet coil and an electromagnetic induction coil are arranged in series close to each other on a coaxial line so that a magnetic flux generated by the internal electromagnet coil passes through the inside of the electromagnetic induction coil. A magnetic field is generated in the cylinder of the cylindrical electromagnetic induction sensor by passing a current through the electromagnet coil, and passes the magnetic material to be measured at a predetermined speed in the cylinder of the cylindrical electromagnetic induction sensor. By letting
A cylindrical electromagnetic induction sensor characterized in that an electromotive force is generated in an electromagnetic induction coil by changing a magnetic field in a cylinder.

[0021]

According to the present invention, a magnetic field is generated in a cylinder by applying a current to an electromagnet coil of the cylindrical electromagnetic induction sensor of the present invention. When the magnetic material to be measured passes through the cylinder of the electromagnetic induction coil at a predetermined speed, the magnetic material to be measured interrupts the magnetic flux and changes the magnetic field. In addition, an eddy current is generated on the surface of the magnetic material to be measured by the frequency applied to the electromagnet coil, and this causes heat loss of the magnetic material to be measured, which changes the magnetic field. These changes in the magnetic field cause the electromagnetic induction coil to generate an electromotive force according to the law of electromagnetic induction. The voltage generated in the electromagnetic induction coil changes in proportion to the volume (weight) of the sample. Therefore,
By setting a weight conversion coefficient that indicates the correlation between the voltage value generated when passing the standard sample at a predetermined speed and the actual weight value, the weight is immediately calculated from the measured output voltage value and specified. can do.

At this time, the magnetic material to be measured is passed through the cylinder of the electromagnetic induction coil at a predetermined speed, and the measurement is performed while the magnetic material is moving. The direction of movement of the magnetic material to be measured is in the direction of the magnetic field in the cylinder. It does not affect the output voltage measured while moving fast in this direction. For this reason,
If the movement of the magnetic material to be measured moves along the direction of the magnetic field in the cylinder, accurate voltage measurement can be performed while moving. However, when the moving speed changes, the measurement voltage varies because the magnetic flux of the electromagnetic induction coil changes with time. Therefore, there is no problem if the magnetic material to be measured is passed at a constant speed.

The voltage of the electromotive force greatly changes depending on the composition, shape, presence or absence of scratches, hardness, and heat treatment of the magnetic material to be measured. Therefore, if there is any difference between the sensor and the standard sample, the sensor can detect and determine the change as the power.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on illustrated embodiments. FIG. 2 is a front view showing the whole of the weight measuring device, FIG. 3 is a plan view of the same weight measuring device, and FIG. 4 is a front view showing a main part of the same weight measuring device. In the drawing, reference numeral 5 denotes an endless belt-type magnetic material transporting means mounted on a base frame 6, and a cylindrical electromagnetic induction sensor 7 disposed substantially at the center of the transporting means 5 has a front surface. Provided on the high base frame on the right side are an analog / digital conversion means 8 electrically connected to the cylindrical electromagnetic induction sensor 7, a voltage measurement means 9, and a calculation means 10. The reference numeral 11 provided on the base end side of the magnetic material transporting means 5 indicates a continuous supply device of the magnetic material to be measured, and the reference numeral 12 provided on the distal end side of the transporting means 5 indicates the magnetic material to be measured. This is an automatic inspection device for material 4 inspection results.

FIG. 5 is an explanatory perspective view showing a combined state of the cylindrical electromagnetic induction sensor 7 and the magnetic material transporting means 5 to be measured. The cylindrical electromagnetic induction sensor 7 is an electromagnet coil 1 wound around the surface of a coil bobbin 3 formed of a synthetic resin. The electromagnetic induction coil 2 is disposed on the inner surface of the coil bobbin 3. The magnetic flux generated by the electromagnetic coil 1 is configured to pass through the electromagnetic induction coil 2, and the magnetic flux generated by the electromagnetic coil 1 is configured to pass through the electromagnetic induction coil 2 when an alternating current is applied to the electromagnetic coil 1. . In the cylinder of the cylindrical electromagnetic induction sensor 7, a belt conveyor type conveying means 5 is disposed so as to penetrate therethrough, and the magnetic material 4 to be measured is transferred at a predetermined speed by driving a driving source. It passes through the cylinder of the sensor 7. Arranged opposite to the front and back of the cylindrical electromagnetic induction sensor 7 with the belt conveyor 13 interposed therebetween is the time during which the magnetic material 4 to be transferred passes through the cylinder of the cylindrical electromagnetic induction sensor 7. (Photoelectric tubes) 14 and 15 for measuring the

The embodiment of the cylindrical electromagnetic induction sensor 7 shown in FIG. 5 is almost the same as the configuration of the operation principle of FIG. FIG.
Is a perspective view showing another embodiment of the cylindrical electromagnetic induction sensor 7. FIG. That is, the electromagnetic coil 1 and the electromagnetic induction coil 2 are arranged in series close to each other on a coaxial line outside the coil bobbin 3 made of synthetic resin so that the magnetic flux generated by the internal electromagnet coil 1 passes through the electromagnetic induction coil 2. It is constituted.
Then, a current is passed through the electromagnet coil 1 to generate a magnetic field A that penetrates into the cylinder of the cylindrical electromagnetic induction sensor 7, and the inside of the cylinder of the cylindrical electromagnetic induction sensor 7 is covered at a predetermined speed. A cylindrical electromagnetic induction sensor 7 characterized in that a magnetic field A in a cylinder is changed by passing a measurement magnetic material 4 to generate an electromotive force in the electromagnetic induction coil 2.

Next, the voltage measuring means 9 will be described. The voltage measuring means 9 is connected to the electromagnetic induction coil 2 of the cylindrical electromagnetic induction sensor 7, and the electromagnetic induction coil 2
The output voltage of the generated electromotive force is measured, the peak value of the output voltage of the induced electromotive force is selected, and digitized by analog-digital conversion means. Specifically, it consists of an oscilloscope, Gauss meter, digital multimeter, mini bridge, personal computer, and the like.

First, the following operation is performed in the dynamic test mode. When an inspection start signal is input from the passage sensor 14, the oscilloscope measures the output voltage of the electromotive force,
One channel of the digital multimeter is converted at any time and the maximum value is stored. When an inspection start signal is input from the passage sensor 14, counting is started by the CTC, and when an inspection end signal is input from the passage sensor 15, the CTC is stopped, and the current count amount is multiplied by the reference period and displayed as a passage speed. I do. The measured maximum value is multiplied by 2.44 mV and displayed as a measured voltage. The measured maximum value is multiplied by the weight conversion coefficient and displayed as the converted weight. The calculating means 9 is a device for calculating the weight by multiplying the numerical value of the measured output voltage by a predetermined weight conversion coefficient, calculating the measured voltage, and calculating the passing speed, and is performed by a personal computer. The converted weight is compared with the upper and lower limit set values. If the set value is within the set range, "non-defective" is turned on, and "OK" is output to the external output. It is set to “OFF” during measurement after 10 mb.

The converted weight is compared with the upper and lower limit set values. If the set weight is larger than the set range, "defective" is turned on and "+ NG" is output to the external output. It is set to “OFF” during measurement after 10 mb. Compare the converted weight with the upper and lower eye set values, and if it is less than the set range, turn on “Defective” and output “−” to the external output.
NG ”. It is set to “OFF” during measurement after 10 mb. The display means 16 is a means for displaying the measured and calculated weight value as it is, for displaying an evaluation judgment obtained by comparing a predetermined standard weight with a weight value, or for displaying both of them.

In the static test mode, the operation is as follows. The converted data is displayed on the converted weight and the measured voltage by the analog / digital conversion means regardless of the inspection start input or the like. The measurement time is not displayed. No data comparison decision is made. Since the weight conversion coefficient is not automatically set, it is set based on the weight measured by another weighing.

When the weight was measured using the weight measuring device according to the present invention, the target value of the measurement accuracy could be cleared from the voltage data as follows. If the measurement time is 0.3 seconds / piece or more, there is no variation in the measured values. Therefore, a workpiece feed speed of 0.5 / piece could be secured. Also, for a measured weight of 40 g, 0.12 g to
With a repeatability of 0.13 g, the target of repeatability of ± 0.5 g was also achieved.

As a result, the measuring time of the present invention is 12 times faster than that of the electronic balance,
It was found that it was a weight measurement method suitable for automation and labor saving, such as high-speed transportation, because it was not affected by the work environment due to non-contact measurement, and was measured during material movement. However, it was found that the measurement accuracy achieved the target for the time being and could be put to practical use, but this point is a future improvement target. Influence of equipment, influence of ambient temperature,
It was found that there were some effects of the static / dynamic test of the work, the influence of the passing speed of the work, the influence of the magnetic field, and the like. It is considered that the measurement accuracy can be further improved by minimizing the influence on these.

[0033]

According to the first aspect of the present invention, the magnetic field is changed by passing the magnetic material to be measured through the magnetic field along the direction of the magnetic field, thereby generating an electromotive force in the electromagnetic induction coil and generating the induced electric power. A weight measuring method characterized in that the output voltage of the electromotive force is measured, and the weight is calculated by multiplying the digitized output voltage value by a weight conversion coefficient. Automated, labor-saving, etc.
A weight measurement method suitable for speeding has been developed.

According to a second aspect of the present invention, there is provided a cylindrical electromagnetic induction sensor which is arranged and formed so that a magnetic flux generated by an electromagnetic coil passes through the electromagnetic induction coil, and a current is applied to the electromagnetic coil to form a cylindrical electromagnetic induction sensor. A magnetic field is generated in the cylinder of the induction sensor, and a magnetic material to be measured is passed through the cylinder of the cylindrical electromagnetic induction sensor at a predetermined speed, thereby changing the magnetic field in the cylinder and generating an electromagnetic induction coil. Electric power is generated, the peak value of the output voltage of the induced electromotive force is measured, converted into a numerical value by an analog-to-digital converter, and the arithmetic unit calculates the weight by multiplying the numerical value of the output voltage by a weight conversion coefficient. This is a weight measurement method as described above, which can also measure weight by contactless measurement from the output voltage of the electromotive force, similarly to the first invention. In methods are, embodying min highly practical gravimetric method specifically private to the instrument have been identified. The present invention is non-contact measurement, and can measure weight at high speed while moving materials, and is not affected by work environment.
It is a weighing method suitable for automation, labor saving, and speeding up in factories and the like.

A third aspect of the present invention is a weight measuring apparatus comprising a cylindrical electromagnetic induction sensor, a magnetic material conveying means to be measured, a voltage measuring means, a calculating means, and a display means. The magnetic material to be measured can be measured automatically and quickly by using the gravimetric method described in the invention and the second invention. Compared with the conventional electronic balance, the measurement time is secured from 0.3 seconds / piece to 0.3 seconds / piece, which is very quick. Although the measurement accuracy is not as good as that of an electronic balance, it is ±
A repetition accuracy of 0.5 g has been achieved, which is sufficiently practical. In addition, non-contact measurement allows the weight to be measured at a high speed while the material is being moved, and has characteristics such as being unaffected by the working environment.

The fourth and fifth inventions are cylindrical electromagnetic induction sensors developed for use in the above-mentioned weight measuring device. This sensor not only measures weight, but also differs in composition such as magnetic metal, difference in heat treatment, difference in secondary metal structure, and difference in hardness. There is also a possibility that it can be used for discriminating differences in quenching, differences in dimensions, etc., and the uses thereof have been greatly expanded.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an operation principle of a cylindrical electromagnetic induction sensor.

FIG. 2 is a front view showing the entire weight measuring device.

FIG. 3 is a plan view of the weight measuring device.

FIG. 4 is a front view showing a main part of the weight measuring device.

FIG. 5 is a perspective view showing a main configuration of the weight measuring device.

FIG. 6 is a perspective view showing another embodiment of the cylindrical electromagnetic induction sensor.

[Description of Main Symbols] 1: Electromagnet coil 2: Electromagnetic induction coil 3: Coil bobbin 4: Magnetic material to be measured 5: Transport means 7: Cylindrical electromagnetic induction sensor 8: Analog / digital conversion means 9: Voltage measurement means 10: Calculation means 13: Belt conveyor 14: Passage sensor (photoelectric tube) 15: Passage sensor (photoelectric tube) 16: Display means

──────────────────────────────────────────────────の Continued on the front page (73) Patent holder 593136100 Kita Nippon Electronics Co., Ltd. 798-3 Kanaya-jihara, Kamiyama-shi, Yamagata (73) Patent holder 593136111 Rebun Engineering Co., Ltd. ) Patentee 593136122 Toa Plating Plant 5--12-12 Miyamachi, Yamagata-shi, Yamagata Prefecture (72) Inventor Hisakichi Katagiri 1453, Kanaya, Toya, Kanaya, Kamiyama-shi, Yamagata Pref. Kazuo Goto 5-6 Sawacho, Kamiyama-shi, Yamagata Tohoku Kogyo Co., Ltd. 2-3-2 Kawasaki, Ishiyama Co., Ltd. (72) Inventor Hiroaki Takahashi 50-2 Shinkanaya, Kamiyama City, Yamagata Prefecture Towa (72) Inventor Atsushi Kiyono Atsushi 798-3, Kanaya-jihara, Kamiyama-shi, Yamagata Prefecture Inside Japan Co., Ltd. (72) Kenichi Yamaguchi 4-3-29 Koshirakawacho, Yamagata City, Yamagata Prefecture Rebun Engineering Limited (72) Inventor Shigeo Okazaki 5-12-12 Miyamachi, Yamagata City, Yamagata Prefecture Inspector, Toa Plating Plant Masayuki Mori (58) Field surveyed (Int.Cl. ⁷ , DB name) G01G 9/00 G01G 17/00 G01G 7/00

Claims (5)

(57) [Claims] 1. A magnetic field is changed by passing a magnetic material to be measured through a magnetic field along the direction of the magnetic field, thereby generating an electromotive force in an electromagnetic induction coil, and an output voltage of the induced electromotive force. And calculating a weight by multiplying the digitized numerical value of the output voltage by a weight conversion coefficient. 2. A cylindrical electromagnetic induction sensor is provided, wherein a magnetic flux generated by an electromagnet coil is provided so as to penetrate through the electromagnetic induction coil. A magnetic field is generated inside the cylinder, and a magnetic material to be measured is passed through the cylinder of the cylindrical electromagnetic induction sensor at a predetermined speed, thereby changing the magnetic field in the cylinder to generate an electromotive force in the electromagnetic induction coil. The peak value of the output voltage of the induced electromotive force is measured and digitized by analog-digital conversion means, and the calculation means calculates the weight by multiplying the numerical value of the output voltage by a weight conversion coefficient. A weight measuring method characterized by the above-mentioned. 3. An electromagnetic induction coil comprising an electromagnet coil and an electromagnetic induction coil, wherein a magnetic flux generated by the electromagnet coil penetrates the electromagnetic induction coil and is formed in the electromagnetic induction coil by changing a magnetic field in the electromagnetic induction coil. A cylindrical electromagnetic induction sensor adapted to generate electric power, and disposed so as to penetrate the cylinder of the cylindrical electromagnetic induction sensor, so that the magnetic material to be measured supplied from the supply means is passed at a predetermined speed. The measured magnetic material conveying means and the electromagnetic induction coil of the cylindrical electromagnetic induction sensor are connected, and the output voltage of the electromotive force generated in the electromagnetic induction coil due to a change in the magnetic field is measured. A voltage measuring means for selecting a peak value of the output voltage and digitizing the value by an analog / digital conversion means, and calculating a weight by multiplying the measured value of the output voltage by a predetermined weight conversion coefficient Display the calculation means and the calculated and calculated weight value as it is, or display the evaluation judgment by comparing the preset standard weight with the measured and calculated weight value, or display both of them A weight measuring device comprising: 4. An electromagnet coil and an electromagnetic induction coil are arranged concentrically so that a magnetic flux generated by an internal electromagnet coil passes through the electromagnetic induction coil, and a current flows through the electromagnet coil. By generating a magnetic field in the cylinder of the cylindrical electromagnetic induction sensor, and passing the magnetic material to be measured at a predetermined speed through the cylinder of the cylindrical electromagnetic induction sensor, the magnetic field in the cylinder is changed to change the electromagnetic field. A cylindrical electromagnetic induction sensor wherein an electromotive force is generated in an induction coil. 5. An electromagnet coil and an electromagnetic induction coil are arranged in series close to each other on a coaxial line so that a magnetic flux generated by an internal electromagnet coil passes through the electromagnetic induction coil.
A magnetic field is generated in the cylinder of the cylindrical electromagnetic induction sensor by applying a current to the electromagnet coil, and the magnetic material to be measured is passed through the cylinder of the cylindrical electromagnetic induction sensor at a predetermined speed, thereby forming a cylinder. A cylindrical electromagnetic induction sensor characterized in that an electromotive force is generated in an electromagnetic induction coil by changing a magnetic field in the inside.