Improved Quantum Hall Standard of Resistance at Electrotechnical Laboratory

Precise Determination of Hydrostatic Pressure Correction Coefficient of Triple Point Cell of Water using Cryogenic Current Comparator Bridge

“…A cryogenic current comparator (CCC) bridge is, at present, the most reliable resistance measuring instrument, the relative uncertainty of which is of the order of 10 À8 or better in ratio measurements. 1,2) The CCC bridge was originally developed for the resistance standards, i.e., to enable the precise comparison of two standard resistors, which are stable and are negligibly dependent on dissipated power. The current amplitude of such a bridge is generally designed to be in the range between 5 mA and 100 mA for resistors between 1 and 100 in order to set the dissipated power smaller than or equal to 10 mW.…”

Accurate periodicity measurement of superconducting quantum interference device magnetic flux response

“…As we reported, 4 change caused by change of the atmospheric pressure. Thermal electromotive force in lead lines connecting the FLL circuit to the L-C circuit or the feedback coil caused offset ͑V th ͒ in the output signal of the FLL circuit: V f = V th 0 when ⌽ = n⌽ o .…”

Improvement of Resistance Ratio Bridge Using Cryogenic Current Comparator by Operating with Low-Noise Voltage Amplifier Using Superconducting Quantum Interference Device for Low Resistance Measurements

“…Resistance ratio bridges using a cryogenic current comparators (CCC bridges) are widely used in national and international metrology institutes for resistance measurement because of their small uncertainties. [1][2][3][4][5][6][7][8][9][10] When measuring resistance ratio, the amplitudes of currents supplied to the resistors are controlled to induce similar voltages, and the small voltage difference is measured.…”

“…We used a Sullivan-type CCC, 16) with 1, 1, 2, 4, 4, 10, 10, 20, 40, 40, 100, 100, 200, 400, 400, 1000, and 1000-turn windings. 12) Its operation principle was based on another CCC bridge designed for resistance measurements from 1 to 10 k, 10) but modified to suit resistance measurement with a current of up to 1 A, as will be explained later.…”

“…Many CCC bridges designed for measuring 1 and higher resistors adopt double-feedback methods, [1][2][3][4][5][6][7][8][9][10] in which fractional current is manually or automatically supplied to a fractional CCC winding in order to adjust I s and equalize voltages of the two resistors (V ¼ 0). Neither a nonlinear dependence of the gain on input voltage (nonlinearity) nor a finite input impedance of the voltage amplifier causes no uncertainties because V ¼ 0.…”