2019.The

quantized Hall resistance (Nobel Prize 1985) plays a crucial role for the realization of this new SI system since this quantum resistance can be used not only for high precision measurements of electrical standards, but also for a new realization of a kilogram by comparing electrical and mechanical forces with the Watt balance.

Pepper, New Method for High-Accuracy Determination of the Fine-Structure Constant Based on Quantized Hall Resistance, Phys.

Dorda, High Precision Measurements of the Quantized Hall Resistance at the PTB, IEEE Trans.

Jeanneret, High-Precision Measurements of the Quantized Hall Resistance: Experimental Conditions for Universality, Phys.

A similarly universal quantity known as the

quantized Hall resistance has more recently become available as a standard for the ohm, the unit of electrical resistance.

We demonstrate that dc quantized Hall resistance (dc QHR) guideline properties and dc and ac QHR values can be measured without changing sample probe lead connections at the QHR device, and report ac QHR values that converge to the dc QHR value when using four-terminal-pair ac QHR measurements.

An important step in developing the ac quantized Hall resistance (ac QHR) [1-10] as an intrinsic impedance standard based on the dc QHR [11-13] is to measure the dc QHR guideline properties [14] and the dc and ac QHR values without changing sample probe lead contacts at the QHR device.

[16] predicts that the largest frequency-dependent correction term in quadruply-connected ac QHR measurements is -[[omega].sup.2][C.sub.X'X'][C.sub.X'X'][R.sub.H][R.sub.H], which involves the squares of: the angular frequency [omega]; the summed-total [C.sub.X'X'] of those wire-to-wire capacitances that have the quantum Hall voltage across them; and the quantized Hall resistance [R.sub.H].) A single ground plane assures symmetry on magnetic field reversal.

The technique exploits a unique property of the quantum Hall effect which allows a

quantized Hall resistance standard to serve as a near-ideal two-terminal resistor whose resistance, 12 906.403 5 W, is essentially independent of the resistance of the room-temperature connecting leads.

NIST determinations of physical constants, namely [[gamma]'sub.p] (26), the Josephson frequency-to-voltage ratio 2e/h (27), the quantized Hall resistance (QHR) in terms of a resistance derived from the calculable capacitor (28, 29), and the moving-coil force-balance determination of the watt (30), were analytically combined (31) in 1989 to obtain values of certain fundamental constants.

Legal Ohm) at NBS in terms of the quantized Hall resistance [R.sub.H] using an 8 T superconducting magnet supplied by Bell Labs.

Williams, NBS determination of the fine-structure constant, and of the quantized Hall resistance and Josephson frequency-to-voltage quotient in SI units, IEEE Trans.