A development trend to reduce the measuring uncertainty of precision measuring instruments is the minimization of the cross-sensitivity of the measuring instruments to disturbance variables. In general, the disturbance quantities include all influence factors acting on the measuring instrument except for the actual measuring quantity itself. An essential role is played by the three climatic quantities 'temperature', 'air humidity' and 'atmospheric pressure'. The state-of-the-art implies that many of today's precision measuring instruments are equipped with an effective disturbance suppression. However, particularly the reduction of moisture dependence offers a high potential for a further lowering of the measuring uncertainty. To achieve this, there are two different approaches available: 1. minimizing the moisture transport responsible for the moisture dependence, or 2. compensating mathematically for the effects of the changes in moisture on the measuring result on the basis of the knowledge of moisture dependence.
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