DEVELOPMENTS OF A WIDE-RANGE CHARACTERIZATION SYSTEM FOR HIGH-T(C) SUPERCONDUCTORS - COMMENT

An improved method is reported for measurements of I-V characteristics of high-T(c) superconductors based upon the acquisition system developed by Kirkup et al. [Rev. Sci. Instrum. 63, 2044 (1992)]. The introduction of a lock-in mode of operation significantly enhances the voltage sensitivity in the range of relevance for the definition of the superconducting state. In addition, this approach permits the current direction in the sample to be reversed whenever needed.