A Josephson Voltage Calibrator

摘要

An automatic voltage calibrator for voltages ranging from -1 V to +1 V is described. The device is based on a Josephson array with Nb-AlO{sub}x-Al-AlO{sub}x-Nb junctions. Being illuminated by microwave radiation with a frequency of 65.2 GHz, the array, in which the operating supply currents of three junction sections are set by a multichannel digital source controlled by a personal computer, generates 21 voltage values quantized with steps of 51.5, 86.6, and 138 mV. The capabilities of this device are demonstrated by studying the deviation from linearity of a seven-digit digital nanovoltmeter with a measurement uncertainty of below 1×10{sup}(-7). By calibrating a precision Zener-diode voltage standard, it is shown that the uncertainty of this calibrator is no more than 20-50 nV at a voltage level of 1 V.