Errors of pressure measurement are considered. The error as a function of the pressure for a vacuum gauge rated at up to 1000 Pa is calculated as an example. It is 0.15 ≤ δp/p ≤ 0.2% over a pressure range of 14 ≤ p ≤ 1000 Pa and it increases hyperbolically up to 100% with p = 0.01 Pa. The parametric reliability of the instrument and its immunity to an accidental increase in pressure the atmospheric level is substantiated. © Springer Science+Business Media, Inc. 2006.