JP2015148596A - Method and device for measuring position of current-carrying part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for measuring a position of a current-carrying part, which is capable of accurately measuring a potential distribution even when a frequency of a flowing high frequency current becomes a high frequency exceeding 10 kHz.SOLUTION: In the method for measuring a position of a current-carrying part, a position of a current-carrying part which does not carry a DC current but carries a high frequency current is measured when an electromagnetic wave leaked from a space between metal plates is evaluated. In this method, a plurality of conductors are connected to a surface of one metal plate of the metal plates, and a surface position of the one metal plate is defined as a measurement point, and a high frequency voltage is applied to feeding points provided on respective surfaces of the metal plates to cause a high frequency current to flow between the metal plates, and the feeding point on the surface of the one metal plate to which the conductors are connected is taken as a reference of potential to measure a potential difference between the measurement point and the feeding points on the surface of the metal plates via a protective board installed so as to isolate the side in which the high frequency current flows and the side in which the potential difference is measured, from each other.

Description

  The present invention relates to the evaluation of electromagnetic wave leakage from an electronic circuit incorporated in an OA / electrical product, and more particularly to a position measuring method and apparatus for a current-carrying part that accurately measures the position of the current-carrying part in the evaluation of electromagnetic wave leakage. It is.

  OA / electrical products are required to shield leakage electromagnetic waves from electronic circuits incorporated in the product. This is because leaked electromagnetic waves may not only cause other OA / electrical products to malfunction, but also may cause electronic devices such as cardiac pacemakers to malfunction and affect people using them. It is.

  The casing of OA / electrical products is often made of a metal such as a steel plate or an aluminum plate. If there is an electromagnetic wave source inside the metal housing, a gap will be created unless the metal plate overlaps the welded part, and electromagnetic waves may leak from here. It becomes a problem. Therefore, a technique for evaluating the strength of the leaked electromagnetic wave based on a mechanism for leaking the electromagnetic wave to the outside of the housing is an important technique for controlling the electromagnetic wave leakage.

  As a technique for evaluating the strength of such leakage electromagnetic waves, there is a technique disclosed in Patent Document 1. This technique measures the position and shape of the current-carrying parts, obtains the interval and length of the current-carrying parts, and evaluates the strength of the electromagnetic waves. In particular, a high-frequency current is passed between the metal plates, It has a feature that the potential distribution generated on the surface can be measured and the position of the energized portion can be measured accurately.

  Prior art documents including non-patent documents referred to in [Mode for Carrying Out the Invention] are shown below.

JP 2009-58324 A

The Institute of Electronics, Information and Communication Engineers, Yoshiyuki Naito, “Microwave / Millimeter Wave Engineering”, Corona, 1986 (First Edition), P.65-71 Edited by the Japan Institute of Metals, “Metal Data Book (3rd edition)”, Maruzen Co., Ltd., 1993, p.14 Susumu Miwa, “High Frequency Electromagnetism”, Tokyo Denki University Press, 1992 (first edition), Appendix (A.1)

  The technique disclosed in Patent Document 1 does not serve as a current-carrying part for direct current, but seeks a current-carrying part as follows even if it is a part that serves as a current-carrying part for high-frequency current. Yes. FIG. 1 is a diagram for explaining the prior art. In the figure, 1 is a metal plate A, 2 is a metal plate B, 3 is a conducting wire, 4 is a high-frequency power source, 5 is a potentiometer, 6 is Ground, and 7 is a feeding point.

  That is, as shown in FIG. 1, a plurality of conductive wires 3 are connected to the surface of the metal plate A1, and the metal plate A1 is disposed so as to overlap the metal plate B2, and the high frequency power source is connected between the plates via the feeding point 7. A high frequency voltage from 4 is applied, and a high frequency current flows between the metal plates. A predetermined gap is provided between the metal plate A1 and the metal plate B2. The potential of the conducting wire at an arbitrary position of the metal plate A1 is used as a reference (hereinafter also referred to as Ground or ground). The potential distribution on the surface of the metal plate A1 is measured as a potential difference from Ground6. The potential difference between the conductors is measured by a potential difference measuring device 5 such as an oscilloscope. The signal from the conductor is amplified by an amplifier if necessary, or input to the potential difference measuring device 5 by removing unnecessary signals with a filter. . Then, an energization unit is obtained based on the measured potential distribution.

  However, in the technique disclosed in Patent Document 1, when the frequency of the flowing high-frequency current becomes a high frequency exceeding 10 kHz, the noise received by the measurement system increases, and the potential distribution may not be measured. There is a problem that the position of the current-carrying part cannot be measured accurately.

  The present invention has been made in view of the problems of these prior arts, and even when the frequency of the flowing high-frequency current becomes a high frequency exceeding 10 kHz, the position of the energization unit can accurately measure the potential distribution. It is an object to provide a measurement method and apparatus.

  In the present specification, high frequency means a frequency of 10 kHz or more in principle.

  The present inventors have found that the above problem can be solved by separating the side where the high-frequency current flows and the side where the potential difference is measured with a metal protection plate, and devising the thickness of the metal plate which measures the potential distribution, The inventors have conceived the present invention described below.

[1] In the evaluation of electromagnetic waves leaking from the gaps between the metal plates, the position of the energized part is measured to measure the position of the energized part when it becomes an energized part with respect to a high-frequency current, although it does not become an energized part with respect to a direct current. In the method
A plurality of conductive wires are connected to the surface of one metal plate of the metal plate, the surface position of the connected metal plate as a measurement point,
Applying a high frequency voltage to a feeding point provided on the surface of each of the metal plates to flow a high frequency current between the metal plates,
The potential difference measurement between the measurement point and the feeding point on the metal plate surface is separated from the side where the high-frequency current flows from the side where the potential difference is measured, with the feeding point on the surface of the one metal plate connected to the conducting wire as a potential reference. Through the protective plate installed in
A method for measuring a position of a current-carrying part, wherein a potential distribution generated on a surface of a metal plate is obtained based on the measured potential difference, and a current-carrying part is determined from the potential distribution.

[2] In the method for measuring the position of the energization unit according to [1] above,
The plate thickness of one metal plate connected to the conducting wire is less than 1.0 mm,
The thickness of the said protection board is a board thickness prescribed | regulated by the following (1) Formula, The position measuring method of the electricity supply part characterized by the above-mentioned.

[3] In the evaluation of electromagnetic waves leaking from the gaps between the metal plates, the position of the energized part is measured to measure the position of the energized part when it becomes an energized part for a high-frequency current, although it does not become an energized part for a direct current. In the device
A high frequency power source for applying a high frequency voltage to a feeding point provided on the surface of each of the metal plates for flowing a high frequency current between the metal plates;
A plurality of conductive wires connected to the surface of one of the metal plates;
A potential difference measuring device for measuring a potential difference between a measurement point which is a surface position of the metal plate to which the conducting wire is connected and a feeding point on the surface of the metal plate, with a feeding point on the surface of one metal plate to which the conducting wire is connected as a reference of potential. When,
A protective plate installed to separate the side where the high-frequency current flows and the side where the potential difference is measured,
An apparatus for measuring a position of a current-carrying part, comprising: means for obtaining a potential distribution generated on the surface of the metal plate based on the measured potential difference, and determining a current-carrying part from the potential distribution.

[4] In the energization unit position measuring method device according to [3] above,
The thickness of one of the metal plates to which the conducting wire is connected is less than 1.0 mm,
The thickness of the said protection board is a board thickness prescribed | regulated by the following (1) Formula, The position measuring apparatus of the electricity supply part characterized by the above-mentioned.

  In the present invention, since the protective plate is installed so as to separate the side where the high-frequency current flows and the side where the potential difference is measured, even when the frequency of the flowing high-frequency current becomes a high frequency exceeding 10 kHz, Potential distribution can be measured.

It is a figure explaining a prior art. It is a figure which shows embodiment of this invention. It is a figure which shows the Example of this invention. It is a figure which shows the result in the Example of this invention. It is a figure which shows the result in a comparative example. It is a figure which shows the relationship between board thickness and the evaluation value ND of noise in case a protection board is iron. It is a figure which shows the relationship between the plate | board thickness and frequency which can be measured when a protection board is iron. It is a figure which shows the relationship between plate | board thickness (0-30 mm) and the evaluation value ND of noise in case a protective plate is aluminum. It is a figure which shows the relationship between board thickness (0-10 mm) in case a protective board is aluminum, and noise evaluation value ND. It is a figure which shows the relationship between the plate | board thickness and frequency which can be measured in case a protective plate is aluminum.

  In the evaluation of electromagnetic waves leaking from the gaps between the metal plates, the present invention does not serve as a current-carrying part with respect to a direct current, but positions of the current-carrying part when it serves as a current-carrying part with respect to a high-frequency current In the measurement method, a high-frequency current is passed between metal plates, and a potential distribution generated on the surface of the metal plate is obtained by measuring a potential difference with the feeding point on the surface of the metal plate as a reference of potential, and an energized portion is determined from this potential distribution. is there.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated, referring an accompanying drawing. FIG. 2 is a diagram showing an embodiment of the present invention. In the figure, the protection plate 8 is a metal plate having a plurality of holes 9. Other reference numerals are the same as those in FIG. In FIG. 2, the front view is shown on the top and the top view is shown on the bottom.

  A high frequency voltage is applied between the two metal plates (metal plate A1 and metal plate B2) arranged so as to overlap from the high frequency power source 4 via the feeding point 7 and by the wiring for feeding, and the high frequency is generated between the metal plates. A current (frequency 1 kHz to 1000 kHz) is applied. The feeding point 7 is provided on the surface of each of the metal plate A1 and the metal plate B2. The feeding point provided on the surface of the metal plate A1 is 7A, and the feeding point provided on the surface of the metal plate B2 is 7B. .

  A plurality of potential measurement points 1 to n are provided on the surface of the metal plate A1, and one conductive wire 3 is connected to each potential measurement point. And the electric potential distribution of the metal plate surface of the metal plate A1 is measured via the conducting wire 3 connected to the potential measurement points 1 to n on the surface of the metal plate A1. At this time, as shown in the figure, a feeding point 7A provided on the surface of the metal plate A1 from the high-frequency power source 4 is set as Ground 6, which is a reference for potential, and the potential difference between the potential measuring points 1 to n and Ground 6 is measured by the potential difference measuring device 5. To determine the potential distribution on the surface of the metal plate A1.

  Although the metal plate A1 is a flat square and the shape of the metal plate B2 is arbitrary, the metal plate A1 is larger than the flat portion of the metal plate B2 (hereinafter referred to as “flange”), and the metal plate A1 is a metal. It is assumed that the flange portion of the plate B2 is completely covered. Further, the flange portions of the metal plate A1 and the metal plate B2 are arranged substantially in parallel, and a predetermined gap is provided between the metal plate A1 and the metal plate B2.

  In order to make it possible to accurately measure the potential distribution even when the frequency of the high-frequency current flowing between the metal plate A1 and the metal plate B2 exceeds 10 kHz, the metal protective plate 8 is provided. Install so that the side where the high-frequency current flows and the side where the potential difference is measured are separated. The protective plate 8 is an iron plate having a size of Δz = 20 mm or more perpendicularly (up and down) from the respective surfaces of the metal plate A1 and the metal plate B2 and Δx = 10 mm or more in the width direction from the end of the metal plate A1. The protective plate 8 is arranged on a plane (XZ plane) perpendicular to the XY plane on which the metal plate A1 and the metal plate B2 are placed, and the shortest distance (Δy) between the protective plate 8 and the metal plate A1 is 5 mm or less. To be. The protective plate 8 and the metal plate A1 (or the protective plate 8, the metal plate A1, and the metal plate B2) may be in contact with each other.

  A plurality of holes 9 (diameter 3 mm or less) are formed in the protective plate 8, and the lead wire 3 for measuring the potential distribution is passed through the hole 9, and the potential measurement points 1 to n on the surface of the metal plate A 1 and Ground 6 are connected. A potential difference measuring device 5 for measuring the potential difference is connected. The conducting wire 3 is connected to the surface of the metal plate A1 from the opposite direction to the power supply wiring. Since measurement is performed using Ground 6 as a potential reference, wiring to Ground 6 is performed in the same direction as that of the conductive wire 3. Note that the influence of noise is reduced if the length of the conductive wire between the metal plate A1 and the protective plate 8 is shortened as much as possible.

  Since the influence of noise is reduced as the plate thickness of the metal plate A1 is reduced, the plate thickness of the metal plate A1 is set to less than 1.0 mm, preferably 0.1 to 0.5 mm. If the plate thickness is less than 0.1 mm, measurement is possible, but the rigidity is low, so it should be 0.1 mm or more. In addition, if the plate thickness is less than 1.0 mm, it is possible to measure without being affected by noise, but in order to further reduce the influence of noise, it is desirable to set the thickness within a range of 0.5 mm or less.

  The thickness of the protective plate is set so as to satisfy the condition of the following formula (1).

  When electromagnetic waves are perpendicularly incident on the surface of the metal body, the electromagnetic waves are attenuated within the metal plate. The thickness at which the electric field (magnetic field) intensity is 1 / e (about 0.37 times) the electric field (magnetic field) intensity on the surface of the metal plate is referred to as the skin thickness (see Non-Patent Document 1, for example).

  This formula (1) defines about 7 times or more as the plate thickness of the protective plate based on the above-mentioned skin thickness, and is found as the lower limit as shown in the examples described later.

  However, if the plate thickness of the protective plate is too thick, the protective plate itself becomes heavy and difficult to handle, and the cost increases, so the upper limit of the plate thickness is 5.0 mm. Further, when the frequency f is 300 Hz or less, the generated noise itself becomes small, so that measurement is possible without a protective plate.

  As described above, the present inventors separate the power supply side and the measurement side with an iron plate protection plate as shown in FIG. 2, and set the thickness of the metal plate for measuring the potential distribution to less than 1.0 mm. It has been found that the above-mentioned problem can be solved by setting the thickness of the protective plate so as to satisfy the condition of the formula (1).

  FIG. 3 is a diagram showing this embodiment. In FIG. 3, the potentiometer is omitted. In addition, a view of the protective plate from the -Y direction is added to the left of the figure below.

  As shown in FIG. 3, between a metal plate A having a thickness of 0.15 mm and a metal plate B having a thickness of 1.2 mm, a resistor having a width of 20 mm and a high dielectric (capacitor) are sandwiched by 10 mm, A current-carrying part was used. An iron plate having a thickness of 1.2 mm was used as a protective plate. This protective plate has 23 holes with a diameter of 3 mm, 5 mm apart, and is provided for the potentiometric lead, and one hole for the ground lead is located 5 mm above the central potentiometer lead. Provided.

  A high frequency voltage of 0.3 Hz to 300 kHz was applied between the metal plates A and B, and the potential distribution on the surface of the metal plate A was measured through the protective plate with the feeding point 7A provided on the surface of the metal plate A as Ground. In the current-carrying part of the metal plate A, current flows (collects) from the periphery of the current-carrying part, and current flows to the metal plate B, so that the potential is lower than the surroundings. That is, the electric potential has a minimum value at the energizing portion.

  The resistor sandwiched between the metal plates A and B becomes a current-carrying part regardless of whether the applied voltage is direct current or high frequency. However, the high dielectric (capacitor) portion has a high impedance when the frequency of the applied voltage is low and does not become a conducting portion, but when the frequency is high, the impedance becomes low and becomes a conducting portion.

  FIG. 4 is a diagram showing the results in this example. When the frequency of the applied voltage is 0.3 Hz, it can be seen that the capacitor portion is not an energization portion, but the resistance portion is an energization portion. And when the frequency of the applied voltage became high and became 10 kHz or more, it was measured that not only a resistance part but a capacitor | condenser part was an electricity supply part.

  FIG. 5 is a diagram showing the results in the comparative example. That is, the results are obtained when the potential distribution is measured at frequencies of 30 kHz and 300 kHz without a protective plate. It can be seen that at a frequency of 30 kHz, the high dielectric (capacitor) portion that has been confirmed in FIG. In addition, at a frequency of 300 kHz, the dispersion of the distribution is large, and it is in a state where the energization part cannot be confirmed. Furthermore, the same measurement was performed when the protective plate was used with the metal plate A having a thickness of 1.0 mm, but the potential distribution could not be measured due to noise.

Therefore, a noise evaluation value ND shown below is defined as a noise evaluation method. When the noise evaluation value ND is 10 ⁻⁵ or more, the measurement becomes unstable (because the variation of the measurement value becomes large), and it is determined that the measurement is impossible.

  First, the reference potential Vr (i) is set to the reference potential at the measurement point i (i = 1 to N) from each potential distribution. Next, the potential distribution is measured by changing the material of the protective plate, the plate thickness, and the frequency of the applied voltage, and the measured value at the same measurement point (i) is defined as V (i). The noise evaluation value ND is defined by the following equation (2). The reference potential may be appropriately determined by a suitable method such as using a measured value measured under appropriate conditions. In this case, the reference potential is the potential measured when an iron plate with a thickness of 1.2 mm is used as the protective plate.

The potential was measured by changing the material of the protective plate, the thickness of the plate, and the frequency of the applied voltage, and the noise evaluation value ND was obtained using equation (2). And the plate | board thickness from which ND becomes less than 10 < ^-5 > was made into the plate | board thickness which can be measured in each frequency.

  FIG. 6 is a diagram showing the relationship between the plate thickness and the noise evaluation value ND when the protective plate is iron. This is the result of examining the relationship between the plate thickness and the noise evaluation value ND by changing the frequency (100 Hz to 300 kHz). FIG. 7 is a diagram showing the relationship between the plate thickness and the frequency at which measurement is possible when the protective plate is iron.

FIG. 7 is based on FIG. 6 and plots the thickness and frequency at which the noise evaluation value ND is less than 10 ⁻⁵ (measured values), and the iron μ and σ are general values. That is, μ = 5.03 × 10 ⁻³ [H / m] (permeability (vacuum) 1.257 × 10 ⁻⁶ (H / m) × relative permeability (iron) 4000), σ = 1.0 × 10 ⁷ [1 / (Ω M)] (see Non-Patent Document 3), the thickness (calculated value) obtained by the above equation (1) is also shown. The measured value is the same as or exceeds the calculated value indicating the lower limit of the plate thickness, and it can be seen that the measurement is possible when the condition obtained by the equation (1) is satisfied.

  Next, an example in which the protective plate is aluminum will be described. FIG. 8 is a diagram showing the relationship between the plate thickness (0 to 30 mm) and the noise evaluation value ND when the protective plate is aluminum. Further, FIG. 9 is a diagram showing the relationship between the plate thickness (0 to 10 mm) and the noise evaluation value ND when the protective plate is aluminum, and shows the plate thickness (0 to 10 mm) in FIG. 8 in an enlarged manner. Is.

As in the case where the above-described material is iron, FIG. 10 is a diagram showing the relationship between the plate thickness and the frequency at which measurement is possible when the protective plate is aluminum. Based on FIG. 8, the plate thickness and frequency at which the noise evaluation value ND is less than 10 ⁻⁵ are plotted (measured values), and μ and σ of aluminum are general values, that is, μ = 1.26. × 10 ⁻⁶ [H / m] (permeability (vacuum) 1.257 × 10 ⁻⁶ (H / m) × relative permeability (aluminum) 1.00) (see Non-Patent Document 3), σ = 3.75 × 10 ⁷ [1 / (Ω · m)] (see Non-Patent Document 2), the thickness (calculated value) obtained by the above equation (1) is also shown.

  The measured value almost coincided with the calculated value indicating the lower limit of the plate thickness, and it was confirmed that even in the case of aluminum, the measurement can be performed when the condition obtained by the equation (1) is satisfied.

  As described above, even when the frequency of the applied high-frequency voltage is a high frequency exceeding 10 kHz, the potential distribution can be measured, and the effectiveness of the present invention can be confirmed.

1 Metal plate A
2 Metal plate B
3 Conductor 4 High frequency power supply 5 Potential difference measuring device 6 Ground
7 Feeding point 7A Feeding point provided on the surface of the metal plate A 7B Feeding point provided on the surface of the metal plate B 8 Guard plate 9 Hole

Claims (4)

In the evaluation of electromagnetic waves leaking from the gap between the metal plates, it does not become a current-carrying part for direct current, but in the method of measuring the position of the current-carrying part when it becomes a current-carrying part for high-frequency current,
A plurality of conductive wires are connected to the surface of one metal plate of the metal plate, the surface position of the connected metal plate as a measurement point,
Applying a high frequency voltage to a feeding point provided on the surface of each of the metal plates to flow a high frequency current between the metal plates,
The potential difference measurement between the measurement point and the feeding point on the metal plate surface is separated from the side where the high-frequency current flows from the side where the potential difference is measured, with the feeding point on the surface of the one metal plate connected to the conducting wire as a potential reference. Through the protective plate installed in
A method for measuring a position of a current-carrying part, wherein a potential distribution generated on a surface of a metal plate is obtained based on the measured potential difference, and a current-carrying part is determined from the potential distribution. In the method for measuring the position of the energization unit according to claim 1,
The plate thickness of one metal plate connected to the conducting wire is less than 1.0 mm,
The thickness of the said protection board is a board thickness prescribed | regulated by the following (1) Formula, The position measuring method of the electricity supply part characterized by the above-mentioned.

In the evaluation of electromagnetic waves leaking from the gap between the metal plates, it does not become an energization part for direct current, but in the position measurement device of the energization part for measuring the position of the energization part when it becomes an energization part for a high-frequency current,
A high frequency power source for applying a high frequency voltage to a feeding point provided on the surface of each of the metal plates for flowing a high frequency current between the metal plates;
A plurality of conductive wires connected to the surface of one of the metal plates;
A potential difference measuring device for measuring a potential difference between a measurement point which is a surface position of the metal plate to which the conducting wire is connected and a feeding point on the surface of the metal plate, with a feeding point on the surface of one metal plate to which the conducting wire is connected as a reference of potential. When,
A protective plate installed to separate the side where the high-frequency current flows and the side where the potential difference is measured,
An apparatus for measuring a position of a current-carrying part, comprising: means for obtaining a potential distribution generated on the surface of the metal plate based on the measured potential difference, and determining a current-carrying part from the potential distribution. In the position measuring device of the energization part according to claim 3,
The thickness of one of the metal plates to which the conducting wire is connected is less than 1.0 mm,
The thickness of the said protection board is a board thickness prescribed | regulated by the following (1) Formula, The position measuring apparatus of the electricity supply part characterized by the above-mentioned.

Images