SOURCES OF UNCERTAINTY IN A DVM-BASED MEASUREMENT SYSTEM FOR A QUANTIZED HALL RESISTANCE STANDARD

Transportable 10 kOMEGA standard resistors have become fairly widespread in industrial, university, and government standards laboratories because of their low temperature coefficient of resistance, ease of transportation, and convenient value. The values of these resistors, however, tend to drift with time, requiring periodic recalibration against an invariant standard such as the quantized Hall resistance. The availability of a simple, inexpensive measurement system for calibrating 10 kOMEGA resistors against such an invariant standard would be of great benefit to primary standards laboratories. This paper decribes a simple automated measurement system that uses a single, high accuracy, commercially available digital voltmeter (DVM) to compare the voltages developed across a 10 kOMEGA 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 kOMEGA standard resistor is determined. The sources of uncertainty in this system are analyzed in detail and it is shown that it is possible to perform calibrations with relative combined standard uncertainties less than 1X10(-7) (0.1 ppm).