Everyday instruments from basic metrology [Basic Metrology]

Usually the excuse given by metrologists for indulging in developing new ways to advance the already incredible reproducibility and coherence of the International System of Units is to quote the miniscule cost involved compared with the trillions of measurements it supports worldwide. However, another justification is that ways of making some simple measurements arose directly out of this research. Some of my ???boys toys??? illustrate this very well.