A result from the NIST watt balance and an analysis of uncertainties

An improved determination of the ratio of power, measured in terms of the J osephson and quantum Hall effects, and also the meter, kilogram, and second , has been completed. The result is expressed as: W-90/W = 1 + (8 +/- 87) x 10(-9). This is an order of magnitude improvement from the fast NIST (form erly NBS) determination. The Type A relative standard uncertainty (statisti cal) is 30 nW/W, and the Type B relative standard uncertainty is 82 n W/W. Type B uncertainty components are listed and discussed within the contest o f experimental procedure descriptions. Improvements for the next version of this experiment are also mentioned.