Development of Electrical Quantities Primary Standards

Abstract

The developments of primary standards for electrical quantities that practically realize the electrical units such as ampere (A), volt (V), ohm (Ω), and farad (F) are introduced in this manuscript. These quantities are achieved in consistency with their definitions. According to the new definition of ampere, current can be realized directly such as single electron transport (SET) pump or indirectly using Ohm’s law. For the SET pump, developments are ongoing as trials to obtain higher current values with lower associated uncertainty to be suitable for metrological applications. With the discoveries of the Effects of Josephson and quantum Hall, it has become possible to consider quantum electrical standards that relate the volt and ohm units to h and e through the Josephson and the von Klitzing constants, respectively. The dc programmable Josephson standard was developed to overcome the problems of conventional standards such as stability and noise immunity with lower cost. Developments are continuing on ac Josephson standards to improve performance and increase output voltages and frequencies. For ac voltage measurements for voltages up to 1000 V, thermal voltage converters are introduced to extend the traceability for measuring the ac voltages in the frequency range from 10 Hz to 100 MHz where quantum-based ac standards still have limitations. Thermal current converters are used as the most accurate and precise standard for measurement of ac currents. The realization of ohm is done by the quantum Hall effect through a quantum Hall resistance (QHR) standard. Developments are occurring to make it simpler, more precise and accurate. The efforts that have been made to increase the values of the resistance quantum hall standard to disseminate its accuracy to other standard resistors to help in industry are also introduced. The farad is practically achieved by the calculable cross-capacitor. The calculable capacitor acts as the ac impedance primary standard because it can transfer the traceability to other impedances by using bridges such as the quadrature bridge. The development is occurring on its displacement sensing system to allow greater accuracy.