Ampere W/V. Current can be measured by a multimeter, a device that can measure electrical voltage, current, and resistance. The standard ampere is most accurately realized using a Kibble balance, but is in practice maintained via Ohm's law from the units of electromotive force and resistance, the volt and the ohm, since the latter two can be tied to physical phenomena that are relatively easy to reproduce, the Josephson junction and the quantum Hall effect, respectively. At present, techniques to establish the realization of an ampere have a relative uncertainty of approximately a few parts in 10, and involve realizations of
Spreading resistance profiling least formula_6 thick. With the aid of calibration resistivity standards, formula_3 can be determined at each probing by the probe pair. A bias of 5mV is applied across the probe tips. The measured resistance can range from 1-ohm to one billion ohms. A "log R" amplifier or electrometer is used to measure the resistance. The modern SRP has two tungsten carbide probe tips placed about 20 um apart. Each tip is mounted on a kinematic bearing to minimize "scrubbing". The probes are lowered very gently onto a beveled piece of silicon or germanium. Although the loading of the probe tips