Standard_Parts_Catalogue

Page 315 | 1.4 Adjusting, Positioning, Locking with and without Position Indication Bull´s Eye, Screw-On and Cross Spirit Levels Technical Information A spirit level is a hollow body filled with a fluid and a gas bubble which is used to check the horizontal position of an object. Definition of terms It is easy to explain how a bull’s eye spirit level works. The hollow body containing the fluid and the gas bubble has a de- fined radius on its top side, causing the gas bubble to always float to the highest point due to its buoyancy. The transparent upper section normally bears markings or a circle centered on the middle position. If the gas bubble is centered precisely inside the marking, the object to be checked (or the reference surface of the spirit level) is in the horizontal position. The function Spirit levels are available as bull’s eye, screw-on or cross spirit levels. The bubble in a bull’s eye spirit level simultaneously indicates the direction and the angle of inclination in the horizontal plane. Screw-on spirit levels only indicate the angle of inclination along the spirit level axis, with no indication of the overall inclination or its direction with respect to the horizontal plane. Cross spirit levels contain two horizontal spirit levels situated at a 90° angle to each other. This allows them to simultane- ously indicate the direction and angle of inclination, with separate indication of the X and Y components. Types of spirit levels The sensitivity of spirit levels is given as angle of inclination, e.g. 30 angular minutes or 0,5 degrees. This is the angle of inclination by which the spirit level must be tilted to make the bubble move by 2 mm. A spirit level with a sensitivity of 6 an- gular minutes therefore has a higher sensitivity than a spirit level with a sensitivity of 30 angular minutes. Sensitivity Difference in altitude Angle w in millimeter per meter in angular minutes Degree, decimal  0,3  1 0,0167  0,9  3 0,0500  1,7  6 0,1000  2,9 10 0,1667  5,8 20 0,3333  8,7 30 0,5000 11,6 40 0,6667 14,5 50 0,8333 17,5 60 1,0000 Sensitivity is sometimes also given in millimeter per meter, i.e. as difference in altitude per unit of length. See also the reference table opposite. Angle of inclination and difference in altitude