Inductive resisitivity measurement with AC-bridge apparatus

✍ Scribed by R. Puranen; M. Puranen; K. Sulkanen

• Book ID: 103964787
• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 404 KB
• Volume: 32
• Category: Article
• ISSN: 0926-9851
• DOI: 10.1016/0926-9851(94)90012-4

✦ Synopsis

A system is presented for measuring the resistivity of highly conducting samples with low-frequency AC-bridges. A sample in the bridge coil is modelled as a sphere placed in a spatially uniform, alternating magnetic field. Model calculations are made using both generally valid formulae and their low-frequency approximations. The calculations show that the out-of-phase response of the bridges and the resistivity of a spherical sample are linearly related at a reasonable accuracy (error below 5%), when the sample has a susceptibility K < 0.2 (SI) and a response parameter W< 2. The latter condition can always be fulfilled by reducing sample size. Using a theoretic relation, which is empirically verified, the low-frequency response of spherical samples is tied to that of non-permeable cylindrical samples with different dimension ratios. The system is calibrated with the aid of lead and bismuth spheres. For cylindrical and spherical samples with low K-values the measuring errors can be kept below 10% in the resistivity range 10-2-10 -7 ~' 2 m.