Limits to calibration: Engineers against nature's stubbornness
Calibration is, by definition, the act of comparison of the indications of an instrument to corresponding quantity values as provided by measurement standards under specified conditions. Surprise and progress in instrument design lurk in the often underestimated adverbial phrase »specified conditions« which supposedly guarantees the repeatability of the measurement process. In fact, what is described as calibration in this definition could also serve in turn as the definition of a quantitative physical experiment. In this sense, complex instruments are »experiments« which constantly push our understanding to higher levels and finer details, and where we finally encounter the fundamental limitations to our measurement procedure. I will take you on a short journey through the calibration of (a) laser based distance measurement device(s) and let you know where specifications need to be taken with a grain of salt.