Sources of Uncertainty in a DVM-Based Measurement System for a Quantized Hall Resistance Standard

National Institute of Standards and Technology, Gaithersburg, MD 20899-0001 TVansporUible lO IcH standard rcstslors h<[ve become fairly widespread in industrial, university, and government standards laboralories because of iheir \tr*/ tempcralurc coefficieni of resistance, ease of iransportaIjon. and convenient value. The values of these resistors, however, tend to drift with lime, requiring jieriodic recalibration against an inv-iu^iant standard such as the quantized Hali resistance. The availability of a simple, inexpensive measuremeni system for calibrating 10 kft resistors against such an invariant standard would be of great benefit to primary standards taboratories. This paper describes a simple automated measuremeru system that uses a single, high accuracy, commercially available digital voltmeter (DVM) to compare the voltages developed across a 10 kil standard resistor and a quantized Hall resistor when the same current is passed through the two devices. From these measurements, the value of the 10 kQ standard resistor is determined. The sources of uncertainty in this system arc analyzed in detail and it is shown thai it is possible to perform calibraltons with lelative combined standard uncertainties less than lXl(r'(0.1 ppm).