Instrumentation techniques for high-temperature superconductor measurement

Methods of measuring the critical temperature T_c, and the critical current I_c for high-temperature superconductors are described. The critical temperature T_c is that at which a normal superconducting transition occurs and is an important parameter in the evaluation of high-temperature superconductors. A four-point resistance measurement is normally used but when the resistance approaches zero, noise and interference dominate the signal. This paper describer how to reduce the noise and interference and extract a signal from the noise. In addition, a new method is described for performing automatic I_c measurements with an oscilloscope or a voltmeter