Best of Both Worlds

摘要

IN A PREVIOUS column, I wrote about the importance of considering instrument resolution in addition to accuracy and precision when estimating measurement uncertainty.1 Let's take that same consideration further. The United States is one country where imperial units and the international system of units (SI) are used widely. In most other countries, only the use of SI-or metric units-is permitted for commerce and legal metrology. Some measuring instruments allow you to display either metric or imperial units at the touch of a button. The digital micrometer is one such instrument. Most digital micrometers display the imperial units in 0.00005-inch resolution. When switched to SI, it displays a resolution of 0.001 mm.