1. Calibration, monitoring: what are we talking about?

To begin with, we need to start with definitions. Definitions of metrology terms have been available since 1978 in the International Vocabulary of Metrology (VIM).

The third edition of the 2012 VIM defines calibration as the operation which, under specified conditions, in a first step establishes a relationship between the values and associated measurement uncertainties provided by standards and the corresponding indications with associated uncertainties, and then in a second step uses this information to establish a relationship for obtaining a measurement result from an indication.

While it is not possible to simplify the definition of VIM, two main ideas can be retained: calibration concerns only the measuring instrument, and calibration consists of a comparison with standards.

The term "surveillance" is not defined...