Note on Weighings Carried Out on the NBS-2 Balance.

Area of Science:

• Metrology
• Mass Measurement
• International Standards

Background:

• The National Bureau of Standards (NBS) balance, now at the International Bureau of Weights and Measures (BIPM), has been crucial since 1972.
• It facilitates comparisons between national prototype kilograms and international standards.

Purpose of the Study:

• To present the nature of systematic biases observed in high-precision mass comparisons.
• To detail the methods used to quantify and eliminate these biases.

Main Methods:

• Utilizing the NBS-2 balance under excellent environmental conditions at BIPM.
• Observing and quantifying systematic biases below 5 micrograms.
• Implementing a remedy to correct measurement results and assigned variances.

Main Results:

• Achieved a long-term standard deviation of 1 microgram (1x10^-9) for 1-kilogram standard comparisons.
• Identified and quantified systematic biases influencing measurements.
• Successfully eliminated the influence of these biases on results and variance.

Conclusions:

• The NBS-2 balance enables highly precise mass comparisons.
• Systematic biases, even at the microgram level, can be identified and corrected.
• Accurate mass standardization relies on addressing subtle measurement influences.