Most of the calibrations described in this guide are laboratory calibrations,
as opposed to field calibrations. To understand what this means, consider an
example where a stopwatch is calibrated in the laboratory against a standard,
and a calibration certificate and/or sticker are issued to the customer. That
same stopwatch or timer can then be thought of as a field standard, a working
standard, or a transfer standard, and used as the measurement reference during
a field calibration. In other words, it can be brought outside the laboratory and
used to calibrate another timing device, such as a parking meter.