| 摘要 |
<p>PURPOSE:A correct errors caused by the temperature dependence of the resistance of a piece of superconducting wire automatically, by measuring the resistance of the superconducting wire when liquid helium reaches a one-point level sensor at the lower end of the superconducting wire, and adjusting an electric circuit by the resistance value. CONSTITUTION:When liquid helium reaches a zero level, i.e., a one-point level sensor at the lower end of a piece of superconducting wire, an analog-switch control circuit 19 triggers an analog switch 20 based on the signal from the one- point level sensor. The switch 20 is switched to the zero side (b) for a specified time. A constant current is applied across both ends of the superconducting wire during this time from a constant current source. The voltage generated across the wire is converted into a current through an input resistor 22. Charge is stored in a capacitor 24. The voltage of said capacitor 24 is held even after the analog switch 20 is switched to the measuring side (a). The voltage is applied to the positive terminal of a differential amplifier as a reference voltage.</p> |
