Axis error

The deviations of the various axes of rotation from the target direction are referred to as axis errors of measuring instruments .

With theodolites and geodetic universal instruments , these are

• the standing axis error (small difference between vertical axis and plumb direction )
• the tilt axis error (angle between tilt and standing axis is not exactly 90 °)
• the sighting axis error (difference between the sighting and optical axes of the telescope).

These influences are reduced by means of dragonflies or inclination sensors. In addition, there are secondary axis errors or wobble errors due to the manufacturing tolerances of the axle bearings (see also rotational movement ).

In the case of the astronomical passage instrument and the meridian circle - where one only observes in the cardinal points - tilting and standing axis errors are determined together and referred to as "inclination errors" (the tilting axis).

In mechanical engineering in addition to these tilt errors even small play curvatures , bending and out of roundness of the axes of a roller, and the imbalance of rotating machine parts. They can be kept within limits through adjustments , special axle bearings and methods of relief and lubrication .