Bifilar AC-DC resistor using a microwire

Bifilar ac-dc resistors of 6.45 k/spl Omega/ to 103.2 k/spl Omega/ consisting of a microwire and a fused silica bar, with extended nominal resistance, improved stability and reduced mechanical sensitivity, have been investigated and fabricated. In this resistor, a fused-silica rectangular bar was inserted between the wires of the bifilar loop to support the microwires and to increase capacitance between the wires. From resistance measurements at ac and dc for several resistors, the frequency correction factor was evaluated to be less than 2/spl times/10/sup -8/ in the frequency range from dc to 1.6 kHz. The resistors can be used as transportable standards for direct comparison with the quantized Hall resistance at both dc and ac, for calibration of the ac standard resistors and the ratio of transformer bridges.