JP2011232063A - Method and device for measuring potential distribution of metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for measuring potential distribution of a metal plate for the purpose of correctly measuring a position of an energization portion when a leak of an electromagnetic wave is assessed.SOLUTION: In this method of measuring potential distribution of a metal plate for correctly measuring a position of an energization portion when a leak of an electromagnetic wave is assessed, potential distribution on the surface of the metal plate is measured by connecting multiple lead wires on the surface of one seamless metal plate and measuring a difference of potential among the lead wires.

Description

  The present invention relates to evaluation of electromagnetic wave leakage from an electronic circuit incorporated in an OA / electrical product or the like, and in particular, a method for measuring a potential distribution of a metal plate for accurately measuring the position of a current-carrying part in evaluating electromagnetic wave leakage, and It relates to the device.

  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 may also cause electronic devices such as cardiac pacemakers to malfunction and affect people who use 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 technology measures the position and shape of the current-carrying part, calculates the interval and length of the current-carrying part, and evaluates the strength of the electromagnetic wave, and evaluates the strength of the leaked electromagnetic wave easily and with high accuracy. There is a feature that can be.

JP 2007-139750 A

In the technique disclosed in Patent Document 1, the electromagnetic wave attenuation is evaluated as follows. That is, as shown in FIG. 1, the intervals between the current-carrying portions 4 when the metal plate 1 and the metal plate 1 are overlapped are d ₁ and d ₂ (d ₁ > d ₂ ). At this time, the maximum distance (d _max ) of the energizing portion is d ₁ , and when electromagnetic waves are transmitted through the gap between the metal plate 1 and the metal plate 1, the attenuation amount of the electromagnetic waves is determined by this d _max . Therefore, seeking d _max by measuring the position of the conductive portion occurring in a portion overlapped metal plates, and estimates the attenuation of electromagnetic waves transmitted through the gap from d _max.

  When two metal plates are stacked, a direct current is applied to measure the position of the energization unit, and the potential distribution is measured. FIG. 2 is a diagram illustrating a potential distribution measurement method when a direct current is applied. A plurality of conductive wires 12 are connected to the surface of one metal plate 1, a direct current is applied to the two metal plates 1 from a DC power source, and the potential difference from Ground at that time is measured with a voltmeter. Measure the potential distribution across the plate surface. The portion where the conductive wire 12 is connected in this way and the potential distribution is measured is a potential distribution measuring portion indicated by a dotted line.

  From the measured potential distribution, the portion where the potential changes discontinuously can be determined as the energization portion. In order to obtain the energization part more accurately, the following method is used.

  A two-dimensional (x, y) potential distribution measured on the surface of the metal plate is defined as V (x, y). When the conductivity of the metal plate is σ, the current density distribution (i (x, y)) is given by equation (1).

  Further, the divergence divi (x, y) is obtained from the above-described current density distribution as shown in the following equation (2).

In the portion where the obtained divergence value is negative, the current is absorbed, and in the portion where the divergence is positive, the current is generated. In this way, the current density distribution is obtained from the potential distribution, and the portion where the divergence is negative (or positive) can be regarded as the energization portion. The distance between the energized portions is measured from the position of the energized portion thus obtained, and the largest value is defined as _dmax .

  FIG. 3 is a diagram showing a method for obtaining the relationship between the current-carrying portion of the portion where the metal plates are overlapped and the characteristics of the electromagnetic wave transmitted therethrough. The upper diagram is a top view and the lower diagram is a side view. In the figure, 5 is a shield box, 6 is a transmitter, 7 is an antenna, 8 is a receiver, 9 is a welded part, 10 is an insulating part, and 11 is an energization measuring part.

  The transmitter 6 is placed in a box-shaped shield box 5 and the intensity of the electromagnetic wave 3 leaking from the edge having a width of 70 mm and a length of 50 mm is measured together with the state of the current-carrying part. (f). The material of the shield box 5 is an electrogalvanized steel sheet having a thickness of 1.2 mm. The edge part (welded part 9) of the edge is welded, and there is no leakage of electromagnetic waves from here. Further, an insulating sheet having a thickness of 50 μm is sandwiched 10 mm inside (hatched portion in the figure) from the edge so that no current is applied (insulating part 10), and electromagnetic waves (output) 3 from the current-carrying measuring part 11 other than the insulating part 10 are applied. Measured by the receiver 8 via the antenna 7 3 m away from the transmitter 6.

  A part of the shield box 5 is a part where the metal plate and the metal plate overlap each other, a current is applied to the part to obtain a current-carrying part, and the characteristics of the electromagnetic wave transmitted therethrough are obtained. Conductive wires 12 are connected to the edge of the shield box 5 by soldering at intervals of 5 mm × 5 mm. A voltage is applied between the metal plates of the edge, a direct current is passed, and a potential difference with respect to the conductor indicated as Ground in the figure is measured for each conductor to obtain a potential distribution. This method is applied when the potential distribution measuring unit has a relatively simple shape such as a square.

  However, the shape of the target potential distribution measurement unit is not necessarily a relatively simple shape. For example, when the shape of the potential distribution measuring portion is as shown in FIG. 4A, it is difficult to form a square hole in the central portion of the metal plate. Therefore, as shown in FIG. 4B, it is conceivable to separate the potential distribution measurement unit into two parts.

In general, a metal lead has a very low resistance, and the resistance is regarded as almost zero. Therefore, when the two parts are connected by a metal conductor, the potential difference between the conductor and the connection part between the parts (between A _{1 and} B _{1 and} between A _{2 and} B _{2 in} FIG. 4B) is almost zero. The two potential distribution measurement units are expected to be regarded as equivalent to the continuous potential distribution measurement unit shown in FIG.

  However, the resistance of the conducting wire portion is larger than the very small resistance in the potential distribution measuring unit, and the two potential distribution measuring units connected by the conducting wire shown in FIG. There is a problem that the potential distribution cannot be measured. That is, for example, the two potential distribution measurement units connected by the conducting wire shown in FIG. 4B cannot be regarded as equivalent to the continuous potential distribution measurement unit (FIG. 4A).

  The present invention has been made in view of these problems of the prior art, and it is an object to provide a method and an apparatus for measuring a potential distribution of a metal plate for accurately measuring the position of a current-carrying portion in evaluating electromagnetic wave leakage. To do.

  The above problems are solved by the following invention.

[1] A method for measuring a potential distribution of a metal plate for accurately measuring the position of a current-carrying part in evaluating electromagnetic wave leakage,
The metal plate is a single continuous metal plate in an arbitrary shape,
A method for measuring a potential distribution of a metal plate, comprising: measuring a potential distribution on the surface of the metal plate by connecting a plurality of conductive wires to the surface of the metal plate and measuring a potential difference between the conductive wires.

[2] In the method for measuring a potential distribution of a metal plate according to [1] above,
A method for measuring a potential distribution of a metal plate, comprising: obtaining a current density distribution from the potential distribution on the surface of the metal plate; and determining a portion where the divergence value of the obtained current density distribution is negative or positive as a current-carrying portion. .

[3] A potential distribution measuring device for a metal plate for accurately measuring the position of a current-carrying part in evaluating electromagnetic wave leakage,
In a state where the metal plate and the metal plate are stacked, a conductive wire connected to the surface of the metal plate,
A potentiometer for measuring the potential difference between the conductors;
A potential of the metal plate, comprising: an arithmetic unit that calculates a potential distribution on the surface of the metal plate from a potential difference measured by the potentiometer, and calculates a position and a shape of a current-carrying portion generated between the metal plates. Distribution measuring device.

  The present invention measures the potential distribution on the surface of the metal plate by connecting a plurality of conductors to the surface of one continuous metal plate in an arbitrary shape, applying a current, and measuring the potential difference between the conductors. Since it did in this way, the position and shape of an electricity supply part can be specified easily and with high precision.

It is a figure which shows the electromagnetic waves which permeate | transmit the part which accumulated the metal plate and the metal plate. It is a figure which shows the electric potential distribution measuring method at the time of applying a direct current. It is a figure which shows the method of calculating | requiring the relationship between the electricity supply part of the part which accumulated the metal plate, and the characteristic of the electromagnetic wave which permeate | transmits there. It is a figure which shows the continuous electric potential distribution measurement part and the separated electric potential distribution measurement part. It is a figure which shows the shape of the electric potential distribution measurement part used by this embodiment. It is a figure which shows the measurement example (the 1) of an electric potential distribution measurement part. It is a figure which shows the measurement example (the 2) of an electric potential distribution measurement part.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to an accompanying drawing. FIG. 5 is a diagram showing the shape of the potential distribution measurement unit used in this embodiment.

  A metal plate having a shape obtained by hollowing out a central part of a square having a width of 140 mm and a length of 140 mm into a mouth shape is used as a potential distribution measuring unit. This metal plate is made of brass with a thickness of 0.2 mm, and is a single continuous plate. The potential distribution measurement unit is connected with conductors at 5 × 5 mm intervals with the origin at 2.5 mm each in the x and y directions in the lower left of the figure.

  A metal plate (made of brass) of 140 mm × 140 mm without a hollow portion was placed on the potential distribution measurement unit, and a current of about 5 A was passed through the metal plate and the potential distribution measurement unit. Here, the metal plate and the potential distribution measurement unit are connected to the plus and minus of the DC power supply.

  Two types of measurement results of potential distribution when the energization part is intentionally changed are shown in FIGS. 6 and 7 is a portion where the current density distribution is obtained from the potential distribution on the surface of the metal plate by the method described above, and the divergence value of the obtained current density distribution is negative or positive. It was judged as a current-carrying part and coincided with the actual current-carrying part.

  6 and 7, it can be seen that the measured potential distribution changes discontinuously and shows extreme values. With a single continuous metal plate, the position of the energization part can be specified based on the above-described equations (1) and (2) from the measurement result of the potential distribution even if the position of the energization part changes.

  As shown in FIG. 4B, when the potential distribution measuring unit is divided into two parts and the separated potential distribution measuring unit is connected by a metal conductor, a metal plate is attached to the potential distribution measuring unit in the same manner as described above. Then, the potential distribution was measured. However, since the potential difference at the conducting wire is large, the potential distribution of the entire potential distribution measuring unit cannot be measured, and the position of the energizing unit cannot be specified.

1 Metal plate 2 Electromagnetic wave (input)
3 Electromagnetic waves (output)
4 Current-carrying part 5 Shield box 6 Transmitter 7 Antenna 8 Receiver 9 Welding part 10 Insulating part 11 Current-measuring part 12 Conductor

Claims (3)

A method for measuring the potential distribution of a metal plate for accurately measuring the position of a current-carrying part in evaluating electromagnetic wave leakage,
The metal plate is a single continuous metal plate in an arbitrary shape,
A method for measuring a potential distribution of a metal plate, comprising: measuring a potential distribution on the surface of the metal plate by connecting a plurality of conductive wires to the surface of the metal plate and measuring a potential difference between the conductive wires. In the electric potential distribution measuring method of the metal plate according to claim 1,
A method for measuring a potential distribution of a metal plate, comprising: obtaining a current density distribution from the potential distribution on the surface of the metal plate; and determining a portion where the divergence value of the obtained current density distribution is negative or positive as a current-carrying portion. . A potential distribution measuring device for a metal plate for accurately measuring the position of a current-carrying part in evaluating electromagnetic wave leakage,
In a state where the metal plate and the metal plate are stacked, a conductive wire connected to the surface of the metal plate,
A potentiometer for measuring the potential difference between the conductors;
A potential of the metal plate, comprising: an arithmetic unit that calculates a potential distribution on the surface of the metal plate from a potential difference measured by the potentiometer, and calculates a position and a shape of a current-carrying portion generated between the metal plates. Distribution measuring device.