JP2001228227A - Magnetic-field measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic-field measuring device with an N-turn-coil magnetic-field probe in which error voltage is reduced and accuracy in magnetic- field detection is improved. SOLUTION: By connecting a reversely wound N-turn coil 13 formed in the opposite direction of winding to an N-turn coil 1 to a coaxial structure tube 14 in a phase opposite to the N-turn coil 1, an unnecessary loop 21 in the direction opposite to an unnecessary loop 10 formed at the part of the lead wire 15 of the N-turn coil 1 is formed, and an error voltage 19 is cancelled out by forming a voltage 20 in the direction opposite to the error voltage 19 which occurs at the unnecessary loop 10 of the N-turn coil 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field measuring device for measuring the intensity of a magnetic field radiated from an electronic device or the like.

[0002]

2. Description of the Related Art In recent years, EMI (electromagnetic noise) measurement using a magnetic field probe has become popular, and there has been an increasing demand for a magnetic field probe capable of detecting a minute magnetic field generated on an electronic device or a circuit board with high sensitivity and high accuracy. ing.

As a magnetic field probe used in a conventional magnetic field measuring device, a sensor such as a near magnetic field probe (HP11940A) manufactured by Hewlett-Packard Company or a near magnetic field probe (MP-10L) manufactured by Nippon Electric Vacuum Glass Co., Ltd. is used. It is generally known to use a coil formed of printed circuit board wiring for the portion. Further, Japanese Patent Application Laid-Open No. 8-129958
In JP-A-10-82845, there is disclosed a magnetic field sensor in which a coil is formed of a microstrip conductor or a strip conductor, and a characteristic impedance is maintained at 50Ω up to a high-frequency range to thereby detect a high-frequency magnetic field.

[0004]

Here, the principle of magnetic field detection using a magnetic field probe used in a magnetic field measuring device will be briefly described. FIG. 1 shows a magnetic field probe using a coil having an arbitrary number of turns (hereinafter, referred to as an N-turn coil, where N is a natural number) in a sensor unit. N-turn coil 1
Is a wiring, for example, the core wire 4 of the coaxial structure line 2 and the outer conductor 3
Connected between When a magnetic field 5 (magnetic flux) interlinks in the N-turn coil 1 whose coil area is S, the magnetic field 5
Current flows in accordance with the magnitude of the current 6 and an induced electromotive force (detection voltage V) proportional to the magnitude of the current 6 is generated at both ends of the N-turn coil 1 by Faraday's law.

[0005] The detection voltage V of this magnetic field probe is expressed by the following equation 1, and is proportional to the area S of the coil and the number N of turns.

V = 2π · f · μ · S · H · N (Equation 1) f: frequency μ: permeability S: area of coil H: strength of magnetic field N: number of turns of coil However, the sensor of the magnetic field probe When the N-turn coil 1 is used in the portion, as shown in FIG. 2, an unnecessary loop 10 for detecting a magnetic field 9 in a direction orthogonal to the magnetic field detection direction 8 of the N-turn coil 1, that is, the N-turn coil 1 is pulled out. A loop constituted by the line 7 is formed.
The magnetic field to be measured does not necessarily exist only in the magnetic field detection direction 8 of the coil, and the voltage detected by the unnecessary loop 10 orthogonal to the coil surface becomes a measurement error.

FIG. 3 shows the directivity of a magnetic field probe using the N-turn coil 1. The directivity of the magnetic field probe means the direction of the magnetic field that can be detected by the probe (coil). For example, if the magnetic field probe is a loop having no unnecessary loop, the directivity is 8 like the directivity 12 shown in FIG. Draw a letter.
It can be seen that the directivity 11 of the N-turn coil having an unnecessary loop has a large voltage detected in a direction (0 degrees, 180 degrees) that is not originally detected. This is because the unnecessary directivity of the loop 10 is combined with the directivity of the coil alone.

Further, in order to improve the sensitivity as well as the resolution of the magnetic field measurement, the size of the coil itself must be reduced. But the smaller the coil, the more
The ratio of the unnecessary loop size of the lead wire portion to the area of the coil increases, and the measurement error increases.

As described above, in the conventional magnetic field probe using the N-turn coil 1, an unnecessary loop formed in the lead wire portion 7 of the coil causes a measurement error, and the magnetic field cannot be measured with high accuracy.

Japanese Patent Application Laid-Open No. Hei 10-311857 discloses a means for reducing a magnetic field interlinking between lead wires of an N-turn coil formed on a multilayer printed circuit board and improving measurement accuracy. It is characterized by means for shielding between the lead lines using a conductive thin film layer.
However, the conductive thin film layer can shield unnecessary loops generated on a surface parallel to the loop surface of the coil formed on the substrate, but cannot shield unnecessary loops perpendicular to the loop surface of the coil.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic field measuring apparatus capable of reducing a measurement error due to a magnetic field interlinking a lead wire portion of a magnetic field probe and measuring a magnetic field to be measured with high accuracy.

[0012]

According to the present invention, there are provided the following two means as a magnetic field probe used in a magnetic field measuring apparatus for achieving the above object.

(1) An error voltage generated in an unnecessary loop is canceled.

For example, in a magnetic field measuring apparatus provided with a magnetic field probe having a coil and a lead wire connected to the coil, and a magnetic field detector for processing information detected by the coil, the magnetic field probe includes the coil and the lead wire. It has a first loop formed by the line and a second loop having an area equal to that of the first loop.

Also, in a magnetic field measuring apparatus having a magnetic field probe having a coil and a lead connected to the coil, and a magnetic field detector for processing information detected by the coil, the magnetic field probe may be a first coil. And a lead from the first coil to form a first loop, and a second coil and a lead from the second coil to form a second loop.

In the above-mentioned magnetic field measuring apparatus,
The first coil and the second coil have the same area and the same number of turns, and the winding directions of the coils are opposite.

[0017] In a magnetic field measuring apparatus provided with a magnetic field probe having a coil and a lead connected to the coil, and a magnetic field detector for processing information detected by the coil, the magnetic field probe may include a first coil. And the area of a first loop formed by a lead from the first coil, and the area of a second loop formed by the second coil and a lead from the second coil. Are equal,
In addition, the lead wire from the first coil and the lead wire from the second coil are connected to each other and share either a positive electrode or a negative electrode.

Also, in a magnetic field measuring apparatus having a magnetic field probe having a coil and a lead wire connected to the coil, and a magnetic field detector for processing information detected by the coil, the magnetic field probe may include a second coil. Has the same coil area as the first coil, has the same number of turns and has the opposite winding, and has an area of a first loop formed by the first coil and a lead wire from the first coil; And the area of the second loop formed by the coil and the wire from the second coil is equal, and the wire from the first coil and the wire from the second coil are connected. In this case, either the positive electrode or the negative electrode of the wiring is shared.

In the above-described magnetic field measuring apparatus,
The lead wire and the magnetic field detector are connected by a coaxial cable.

In the above-described magnetic field measuring apparatus,
The coil is formed using a wiring board.

More specifically, in the magnetic field probe, an N-turn coil for detecting a magnetic field, a reverse-wound N-turn coil for canceling a detection voltage generated in an unnecessary loop of the magnetic field probe, and the N-turn coil A coil, and a wiring from the reverse-wound N-turn coil to the magnetic field detector, for example, a coaxial structure line portion, wherein the N-turn coil has a lead wire for connecting to the coaxial structure line portion at both poles, The coil is connected by a lead wire between the core wire of the coaxial structure line portion and the outer conductor, and the reverse-wound N-turn coil is formed in a reverse winding with the same loop area as the N-turn coil,
By connecting the reverse-turned N-turn coil to the coaxial structure line section in a phase opposite to that of the N-turn coil, an unnecessary loop (first loop) formed by the N-turn coil and the lead wire section is oppositely directed. To form a second loop to cancel the error voltage generated in the first loop.

The first loop and the second loop are as follows.
For example, it is shown in FIGS. 12 and 14, which is composed of an N-turn coil and a lead wire, in which a magnetic flux links.

(2) No unnecessary loop is formed.

A coil for detecting a magnetic field, a wire connected to the magnetic field detector, and a lead connecting the wire and the coil are provided, and one of the leads is connected to one end of the coil from the end of the coil. The wire is turned back, passes through the coil, and is connected to the wiring together with the other lead wire at a position passing through the coil.

More specifically, the magnetic field probe of the present invention has an N-turn coil for detecting a magnetic field, and a coaxial structure line portion which is a wiring from the N-turn coil to the magnetic field detector. The coil is provided with a lead wire portion for connecting to the coaxial structure line portion at both poles, and one of the lead wires passes directly from the end of the coil through the center of the coil, and the other from where the coil passes through the coil. By connecting to the coaxial structure line portion in a state of being wound around the lead wire in a twisted form, an unnecessary loop is not formed, and the error voltage is reduced.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.

(Embodiment 1) First, a first embodiment of the present invention will be described.

As shown in FIG. 4, the magnetic field probe according to the present embodiment has an N-turn coil 1 formed in a loop shape with a conductor, for example, a circular loop or a square loop, and a loop shape with a conductor, for example, a circular loop. It comprises a reverse-wound N-turn coil 13 formed in a rectangular or square loop shape, and a coaxial tube 14 having a coaxial structure line. The magnetic field detected by the N-turn coil 1 and the reverse-turn N-turn coil 13 is detected as voltage information shown in FIG. That is, the magnetic field detected by the N-turn coil 1 and the reverse-turn N-turn coil 13 is transmitted to the spectrum analyzer via a lead wire 15 and a wiring, for example, a coaxial tube 14 and a coaxial structure line (not shown) connected to the end thereof. Are detected as voltage information by a magnetic field detector (not shown). Here, the reverse-wound N-turn coil 13 has the same size (coil area S, number of turns N, and coil length L) as the N-turn coil 1, and the winding direction of the coil is opposite to that of the N-turn coil 1. It is a coil formed so that it becomes.

The reverse-turned N-turn coil 13 and the N-turn coil 1 are connected between the core wire 16 of the coaxial tube 14 and the outer conductor 17 by lead wires 15 of both poles so as to be aligned with the center axis 18 of the coil. You. Further, both coils are connected to the coaxial tube 14 so that the phases are opposite to each other. The opposite phase is achieved by sharing either the positive electrode or the negative electrode of the wiring to which the lead wire from the N-turn coil 1 and the lead wire from the reverse-wound N-turn coil 13 are connected. For example, as shown in FIG. 4, the plus (+) pole of the N-turn coil 1 is
, The positive (+) pole of the reverse-wound N-turn coil 13 is also connected to the core wire 16 of the coaxial tube 14. At this time, as shown in FIG. 5, an unnecessary loop 10 (first loop) orthogonal to the loop surface of the coil is formed at the portion of the lead wire 15 of the N-turn coil 1, and a magnetic field is generated in the first loop. If 5 is linked in a direction from the front to the back of the page, an error voltage 19 is generated in the direction of the arrow. However, by connecting the reverse-wound N-turn coil 13 to the N-turn coil 1 in the opposite phase, a cancellation loop 21 (second loop) having the same size as the first loop 10 and having the opposite phase is formed, and the error voltage is increased. The error voltage 19 can be canceled by generating the voltage 20 in the direction opposite to the direction 19.

As described above, by forming the second loop having the same size as the first loop in the opposite phase, the error voltage can be canceled and the magnetic field can be measured with high accuracy. In addition,
The detected voltage may be either the voltage applied to the N-turn coil 1 or the voltage applied to the reverse-turned N-turn coil 13 as shown in FIG.

In FIGS. 4 and 5, a simple air-core coil is used as the coil, but it is also possible to use a ready-made inductor component having an N-turn coil formed therein. Further, by inserting a magnetic material having the same length as the length of the coil or a length penetrating the coil inside the coil, the magnetic permeability in the coil can be increased and the sensitivity of the magnetic field probe can be further improved. These means are the same in the magnetic field probe of each embodiment described later.

In the first embodiment, the plus (+) poles of the N-turn coil 1 and the reverse-wound N-turn coil 13 are connected to the core wire 16 of the same coaxial tube 14. It is needless to say that the same effect can be obtained even if the measurement error is canceled by measuring and measuring the same magnetic field with the reverse-wound N-turn coil 13 and processing the separately measured values.

(Embodiment 2) Next, a second embodiment of the present invention will be described.

In the magnetic field probe according to the first embodiment, the N-turn coil 1 and the reverse-turn N-turn coil having the same size are formed in order to cancel the error voltage by forming a loop having the same size as the unnecessary loop in the opposite phase. When forming 13 with a conducting wire, it was necessary to minimize the variation in the shape of the coil. Further, it is necessary to suppress connection variations when connecting the two coils to the coaxial tube 14. Therefore, in the present embodiment, the circular or square loop-shaped N-turn coil 1 and the reverse-wound N-turn coil 13 and the lead-out wiring are formed on a multi-layer substrate to suppress variations in probe manufacturing such as shape variations and connection variations. . Thereby, it is possible to form an N-turn coil having a more accurate loop area than forming a conductor. Hereinafter, a specific description will be given.

FIG. 6 shows a main part of the multilayer substrate magnetic field probe in the case where the number of windings is three turns (N = 3). The three-turn coil multilayer substrate magnetic field probe shown in FIG. 6 includes a three-turn multilayer substrate coil 22 formed using the second to fourth layers, and a reverse-wound three-turn multilayer substrate coil formed using the sixth to eighth layers. A coil 23, a first layer simulating a lead wire with a multilayer substrate,
It is composed of a strip structure wiring 24 composed of a fifth layer and a ninth layer. An N-turn coil using a multilayer substrate is formed by connecting wiring coils of each layer, for example, a printed wiring coil 25 with through holes 26. Therefore, compared to the N-turn coil 1 formed by using the conductive wire, the variation in shape is small, and the both ends of the two coils are directly wired to the strip structure wiring 24, so that no connection variation occurs.

The printed wiring coil 25 of each layer is
It is possible to form a multilayer N-turn coil by changing the number of layers even if a half-turn coil or a turn coil of other length is used instead of one turn.

The magnetic field detected by the three-turn multilayer board coil 22 and the reverse-turned three-turn multilayer board coil 23 shown in FIG. 6 is applied to the strip structure wiring 24 and the wiring connected thereto, for example, the connector 28 as shown in FIG. 29 and a magnetic field detector such as a spectrum analyzer via a coaxial cable 30, for example, as voltage information.

Here, the reversely wound three-turn multilayer substrate coil 23
Has the same size (loop area S, number of turns N, and coil length L) as the three-turn multilayer board coil 22 and the winding direction of the coil is three-turn multilayer board, as described in the first embodiment. The coil is formed so as to be in the opposite direction to the coil 22. The reverse-turned three-turn multilayer board coil 23 and the three-turn multilayer board coil 22 are formed between the signal line 32 and the outer conductor 33 of the strip structure wiring 24 so as to have opposite phases to each other. For example, when the plus (+) pole of the three-turn multilayer board coil 22 is connected to the signal line 32 side of the strip structure wiring 24 as shown in FIG. It is connected to the signal line 32 side of the strip structure wiring 24.

In this case, an unnecessary multilayer substrate loop 35 (first loop) in a direction orthogonal to the loop surface of the multilayer substrate coil is formed by the three-turn multilayer substrate coil 22 and the strip structure wiring 24, and the magnetic field in FIG. When 5 interlinks, an error voltage 36 is generated in the direction of the arrow. However, by connecting the reverse-wound three-turn multilayer substrate coil 23 in the opposite phase to the three-turn multilayer substrate coil 22, the same size as the first loop 35 is obtained. By forming the canceling multilayer substrate loop 37 (second loop) having the opposite phase and generating the voltage 38 in the opposite direction to the error voltage 36, the error voltage 36 can be canceled.

As described above, even in the magnetic field probe using the multilayer substrate, the second loop having the same size as the first loop is formed in the opposite phase in the direction along the central axis.
The error voltage can be canceled out, and the magnetic field can be measured with high accuracy.

The voltage detected is a three-turn multilayer substrate coil 22 or a reverse-turned three-turn multilayer substrate coil 23.
Voltage may be applied.

In the second embodiment, the plus (+) poles of the three-turn coil 22 and the reverse-turned three-turn coil 23 are commonly connected in the fifth layer. It is needless to say that the same effect can be obtained even if the same magnetic field is measured by the reverse-wound three-turn coil 23 and the separately measured values are arithmetically processed to cancel the measurement error.

Although the case where the number of turns of the coil is 3 has been described in the second embodiment (N = 3), it goes without saying that the same effect can be obtained even if the number of turns of the coil is arbitrary. Absent.

(Embodiment 3) First, a third embodiment of the present invention will be described.

As shown in FIG. 9, the magnetic field probe of the present embodiment has an N-turn coil 61 formed in a circular loop shape (or a square loop shape) by a conductive wire 62 whose outer skin is insulated.
And a coaxial tube 64 of a coaxial structure line. Here, the N-turn coil 61 is connected between the core wire 66 of the coaxial tube 64 and the outer conductor 67 by a lead wire.
3 is formed so as to be folded back from the end of the coil so as to pass through the center of the coil as it is, and further wired from the point passing through the coil to the coaxial tube 64 in the form of a twisted wire wound around the other lead wire 68, By minimizing unnecessary loops where the magnetic field interlinks other than the loop surface of the N-turn coil 1, the error voltage can be reduced and the magnetic field can be measured with high accuracy.

FIG. 10 shows an example of a main part of a measuring apparatus using the magnetic field probe shown in the first to third embodiments.
The magnetic field probe mounting portion 55 to which the magnetic field probe 42 is mounted can be driven to any position and direction by the θ direction probe rotating mechanism 54, the X direction probe driving mechanism 51, the Y direction probe driving mechanism 52, and the Z direction probe driving mechanism 53. Thus, the magnetic field probe 42 can measure a magnetic field radiated from the measured object in an arbitrary direction.

In FIG. 10, the position of the probe is located above the object to be measured. However, the effect of the present invention is that the position of the probe is located below the object to be measured or It is needless to say that the same effect can be obtained even if both are positioned.

FIG. 11 is a diagram of an entire magnetic field measuring apparatus using the magnetic field probes shown in the first to third embodiments.
For example, the detected magnetic field signal 4 detected by the magnetic field probe 42
9 is processed as a voltage value by the electromagnetic field detector 43, is subjected to arithmetic processing or the like on the magnetic field intensity at the measurement position by the memory 46 and the computer 45, and the processing result is displayed on the display device 47. Further, for example, the measurement start position, the measurement end position, and the like are input to the input device 48, and the unnecessary radiation from the measured object is measured while controlling the measurement position of the probe by the computer 45 and the motor controller 44.

[0049]

As described above, according to the present invention,
It is possible to provide a magnetic field measuring apparatus capable of reducing a measurement error due to a linkage of a magnetic field to a lead line portion of a magnetic field probe and measuring a measured magnetic field with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the principle of magnetic field detection by a magnetic field probe.

FIG. 2 is an explanatory diagram showing a problem in a conventional magnetic field probe.

FIG. 3 is an explanatory diagram showing directivity of a conventional N-turn coil magnetic field probe.

FIG. 4 is an explanatory view showing an N-turn coil magnetic field probe structure according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the structure and features of an N-turn coil magnetic field probe according to the first embodiment of the present invention.

FIG. 6 is an explanatory view showing the structure and features of an N-turn multilayer substrate coil magnetic field probe according to a second embodiment of the present invention.

FIG. 7 is an explanatory view showing the structure and features of an N-turn multilayer substrate coil magnetic field probe according to a second embodiment of the present invention.

FIG. 8 is a sectional view showing the structure of an N-turn multilayer substrate coil according to a second embodiment of the present invention.

FIG. 9 is an explanatory view showing the structure and features of a magnetic field probe according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a main part of a measuring device using the magnetic field probe of the present invention.

FIG. 11 is a diagram of a magnetic field measuring apparatus using the magnetic field probe of the present invention.

FIG. 12 is a diagram showing a loop area according to the first embodiment of the present invention.

FIG. 13 is a diagram showing a loop area according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... N-turn coil 2 ... Coaxial structure line 3 ... Coaxial structure line outer conductor 4 ... Coaxial structure line core 5 10 ... unnecessary loop 11 ... directivity of N-turn coil 12 ... directivity of coil having no unnecessary loop 13 ... reverse-turned N-turn coil 14 ... coaxial tube 15 ... lead wire 16 ... core wire of 14 17 ... outer conductor of 14 Reference Signs List 18 central axis 19 error voltage 20 voltage in the opposite direction to 19 21 cancellation loop (second loop) 22 three-turn multilayer substrate coil 23 reverse-turn three-turn multilayer substrate coil 24 strip wiring 25 printed wiring Coil 26 ... Through hole 27 ... Connector pad 28 ... Connector (female) 29 ... Connector (male) 30 ... Coaxial cable 3 ... signal line 33 ... outer conductor 35 ... unnecessary multilayer substrate loop 36 ... error voltage 37 ... offset multilayer substrate loop 38 ... voltage in the opposite direction to 36 39 ... pedestal 40 ... DUT 41 ... probe movable stage 42 ... magnetic field probe 43 ... magnetic field detector 44 ... motor controller 45 ... control computer 46 ... memory 47 ... display device 48 ... input device 49 ... detected magnetic field signal 50 ... stage control signal 51 ... X-direction probe drive mechanism 52 ... Y-direction probe drive mechanism 53 ... Z-direction probe drive mechanism 54... Θ-direction probe rotation mechanism 55... Probe mounting part 56... Stage control cable 61... N-turn coil 63... Lead wire 64... Coaxial tube 66.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taku Suga 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Technology Research Institute F-term (reference) 2G017 AA01 AB07 AD04 BA10

Claims (7)

[Claims] 1. A magnetic field measuring apparatus comprising a magnetic field probe having a coil and a lead wire connected to the coil, and a magnetic field detector for processing information detected by the coil. A magnetic field measuring apparatus comprising: a first loop formed by a line; and a second loop having an area equal to that of the first loop. 2. A magnetic field measuring apparatus comprising: a magnetic field probe having a coil and a lead wire connected to the coil; and a magnetic field detector for processing information detected by the coil. And a lead from the first coil to form a first loop, and a second coil and a lead from the second coil to form a second loop. 3. The magnetic field measuring apparatus according to claim 2, wherein
A magnetic field measuring apparatus, wherein the first coil and the second coil have the same area and the same number of turns, and the winding directions of the coils are opposite. 4. A magnetic field measuring apparatus comprising: a magnetic field probe having a coil and a lead wire connected to the coil; and a magnetic field detector for processing information detected by the coil. And the area of a first loop formed by a lead from the first coil, and the area of a second loop formed by the second coil and a lead from the second coil. A magnetic field measuring apparatus, wherein both the positive electrode and the negative electrode of a wire to which the lead wire from the first coil and the lead wire from the second coil are connected are shared. 5. A magnetic field measuring apparatus comprising: a magnetic field probe having a coil and a lead wire connected to the coil; and a magnetic field detector for processing information detected by the coil. Has the same coil area as the first coil, has the same number of turns and has the opposite winding, and has an area of a first loop formed by the first coil and a lead wire from the first coil; And the area of the second loop formed by the coil and the wire from the second coil is equal, and the wire from the first coil and the wire from the second coil are connected. A magnetic field measuring apparatus characterized in that either a positive electrode or a negative electrode of a wiring to be used is shared. 6. A magnetic field measuring apparatus according to claim 1, wherein said lead wire and said magnetic field detector are connected by a coaxial cable. 7. A magnetic field measuring apparatus according to claim 1, wherein said coil is formed using a wiring board.