Transmille provides specifications as both Absolute and Relative Specification, with varying calibration intervals, from 24 Hours to 2 Years
By 'Absolute Uncertainties', this means that all internal components of the calibrator have been compensated for. This includes stability, line voltage variations, temperature, humidity as well as the uncertainty of calibration as performed by Transmille Ltd.
This does NOT include external sources of uncertainty, such as the leads that are used to connect to the calibrator and resolution of the UUT
'Relative Accuracy' refers to the stability of the instrument itself, without any external factors except temperature variation.
During re-calibration, the 'Absolute Uncertainties' should be used for verification of the instrument.
If the calibration laboratory offers better uncertainties than those offered by Transmille, new uncertainties can be calculated by combining the relative specification and the new imported uncertainties.
All of Transmille's Absolute uncertainties are presented to 95% confidence, k=2.This is for ease of use in a 17025 accredited laboratory, where other contributions will likely also be calculated for k=2, minimizing the need for re-calibration of uncertainties.