MEASURING METHOD FOR AC RESISTANCE OR AC EQUIVALENT RESISTANCE OF SUPERCONDUCTOR

摘要

PURPOSE:To evaluate a superconductor in a short scale by employing an insulation amplifier and a lock-in amplifier, evaluating a high frequency signal of odd magnification of a basic wave, and increasing the impedance of a current loop. CONSTITUTION:A current conducted to a sample 1 by power obtained from an oscillator 2 and a power amplifier 3 is evaluated at its value I by a C.T. and an AC current measuring system 5. Its current loop is floated from a ground, a resistor 9 is connected in series, the output of the amplifier 3 is conducted as a predetermined voltage, and a voltage generated at the sample 1 is detected by a voltage lead 7. In this case, a common mode noise is removed from a signal becoming only a loss voltage by the correction with a variable mutual induction coil 8 by an insulation amplifier 10, and differentially amplified. This is further read at a basic wave voltage and an odd order high frequency voltage by a lock-in amplifier 11 connected synchronously with the oscillator 2. The evaluation of the sample 1 is calculated by a computer processing system 14 from the measured loss voltage and the current value I of the amplifier 11.