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.
The device was connected in series with a temperature-controlled, wire-wound resistor, with a value trimmed to within about 1 x [10.sup.-6] of the Hall resistance [R.sub.H] at i = 4 (i.e., 6 453.201 75 [ohm]).
This is perhaps one of the most important results from a metrological perspective, since frequently one uses [R.sub.x] as a guideline for identifying proximity to h/[ie.sup.2] in the Hall resistance.
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  and the dc and ac QHR values without changing sample probe lead contacts at the QHR device.
It will serve as a "turnkey" primary representation for capacitance, provide an additional route for the measurement of the fine-structure constant and provide a means to close the "quantum metrology triangle" formed by the Josephson voltage, the quantum Hall resistance
, and the fundamental electron charge.
A NIST scientist has developed a new technique that enables more accurate scaling from the primary NIST quantum Hall resistance
standard to high resistance levels of 1 M[ohm] and above.
This current is measured as a voltage drop that is generated as it passes through a resistance calibrated against the quantum Hall resistance
. The voltage is measured directly against a Josephson voltage standard.
Legal Ohm was re-defined in terms of the QHE, with the internationally-accepted value of the quantum Hall resistance
(or von Klitzing constant, after the effect's discoverer) based on calculable ca pacitor experiments and other fundamental constant determinations.
By producing samples of sufficient size and quality, and accurately demonstrate Hall resistance
, the team proved that graphene has the potential to supersede conventional semiconductors on a mass scale.