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Hitachi

Corporate InformationResearch & Development

December 18, 2015

Report from Presenter

Korea-Japan Joint Conference 2015 (KJJC2015) was held at Sendai International Center in Sendai-shi, Japan on November 23 - 24, 2015. KJJC is one of the conferences focused on Electromagnetic Theory, Electromagnetic Compatibility, and Biology and Medicine Electromagnetics area. This conference is hosted by IEICE and KIEES (Korea), and the IEEE co-sponsorship. Researchers of the company and the university from Japan and Korea attended this conference and discussed ET/EMC/BM technologies and its applications animatedly.

This report shows the title of the presentation is "A Measurement Method for Housing Surface Low-Frequency Noise Current". This presentation is about the high sensitive magnetic field sensor system to visualize the noise current of the surface.

In the apparatus for industrial and medical application, the weak surface current noise spread into the cables and frame from the internal power supply or digital circuits generally affects the precision and degrades the performance of the equipments. This noise distribution visualization system is developed by measuring the magnetic field caused by the current noise spread in the frame and cables. This system can be used to obtain the current distribution and identify the noise source.


Fig. 1 2-D flux-gate sensor and assembly
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Fig. 2 Geomagnetism cancel
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Fig. 3 A prototype of the surface current
measurement system

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The surface current measurement system is composed of a 2-D flux-gate sensor which is sensitive for the low frequency magnetic field, a 6-axes position and angle sensor, and a processing unit which converts the magnetic field data to the current vector data and plots them with 3-D. In order to measure the narrow parts of industrial equipment and a car, the magnetic field sensor is located on one edge of a thin stick and the position and angle sensor are located on the other edge. Flux-gate sensor which has high sensitivity for low frequency magnetic field is used.

On the other hand, Flux-gate sensor is sensitive to DC magnetic field and is subject to the earth magnetism. A coil is used to cancel the DC magnetic field corresponding to geomagnetism in the proposed system and the influence of geomagnetism is eliminated (Fig. 1, Fig. 2).

The detected magnetic field position and direction is calculated from the position and angle sensor data. Fig. 3 shows prototype system. The position error of the target measurement point is ≤30 ㎜ (Fig. 4). The performance of the proposed system is confirmed by a prototype experiment. The 3-D current noise distribution is plots as Fig. 5. We will apply this system to our product and will contribute to solid development of products in future in electromagnetic environment.


Fig. 4 FG Sensor Measurement Result
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Fig. 5 3-D current noise distribution
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