In metrology, simpler is better [Recalibration]

The theme of this article originates from an apparent paradox. When the need arises to make a more accurate or more convenient measurement, it might be supposed that it is best to update the existing method with additions whose purpose is to eliminate systematic errors. But, in fact, it seems that additions often result in less convenience and even more places in which errors can hide. The history of measurement demonstrates that much better progress is often made by starting again with something simpler which is closer to first principles, which minimizes the number of measurements to those suggested by the dimensionality of the measurand, and which directly satisfies the defining conditions of the quantity to be measured. We can understand this best by using actual examples. I include examples from metrology that have improved the SI units in the measurement of gravitational acceleration in measuring weight, in equating the mechanical and electrical SI units of power using a watt balance, and measuring the quantum Hall effect. Other examples will easily come to mind for all kinds of measurements. My hope is that understanding this drive to simplify in order to achieve the ultimate attainable accuracy in setting up the SI units will help the design of better measurements in general.