Novel Technique for Contactless Estimation of Electrical Conductivity of Paramagnetic Materials

Measurement of room temperature electrical conductivity of metals (both porous and composite metals) has been a subject of interest for researchers since it is useful in determining some important mechanical properties that are critical in industry especially aerospace structures. The most widely accepted method of D.C room temperature electrical conductivity is the Vander Pauw method that requires extremely sensitive ammeter capable of measuring currents less than a micro ampere. This paper reports the results of experiments with discs of varied materials of known conductivity using the rotating disc type energy meter and relate the conductivity with the rotational speed of the disc. Previous efforts have shown that replacement of discs inside the slot is difficult, and discs of different diameter are not possible. This is achieved by using a small Servo motor in place of energy meter. Discs of varied materials are fabricated, and the rotation of disc is accomplished by attaching them on to the shaft of the motor. Replacement of discs is made possible by providing a threading arrangement in the motor shaft. Experiments are conducted by measuring the change in rotating speed (retardation) of the disc. The work reported is a first step toward obtaining a calibration curve that can relate the electrical conductivity with a significant experimentally measurable parameter like slip. This novel technique is expected to lead toward the development of a low-cost device and technology to assess the electrical conductivity of metals and composite metals including materials with pores.