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Yamada K.,Saitama University | Luo J.,Saitama University | Shimoji H.,Regional Technological Collaboration Promotion Bureau | Nakahata Y.,Regional Technological Collaboration Promotion Bureau | And 5 more authors.
Przeglad Elektrotechniczny | Year: 2011

We have been investigated a basic concept of material constant evaluation using transformer type probes in an a.c. field range between 20Hz and 200kHz. The probes are consisted of 2 transformers with open magnetic poles attached to the material surface under estimation and attached to the reference material, respectively. The output voltage of each transformer is connected in series and reverse to cancel the offset voltage caused by the leakage flux. The analyses are performed by using a.c. magnetic resistance theory of magnetic circuit. We attained the high sensitivity of conductivity and permeability changes in the material without direct contact as that in d.c. measurements. The transfer function of material in general was defined by the experimental results of the excitation current of the probe, operation frequency and the output voltages, independent of the characteristics of the transformer materials.

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