Spirit Levels
Princible A gas bubble subject to the buoyancy in a liquid adjusts along a curved path to a stable equilibrium position. The zero position is marked. |
Forms A) visibly curved, one-sided and unpolished tubular levels B) internally barrel-shape polished tubular levels C) circular levels with internally concave polished base plates D) special levels with temperature chambers, spheres, different scalings etc. |
Definition according to DIN 1319- Sensitivity = bubble way divided by propensity |
Bubble The bubble size of tubular levels is about one third of the total length at 20 degrees (Celsius) operating temperature. With increasing temperature the bubble decreases. With decreasing temperature the bubble increases. |
Units Angular dimensions in degrees, minutes and seconds; radian measure (tangent) in millimeter per meter, rarer radius or per mille. |
Filling Mostly heptane or dehydrated gasoline for tubular levels. Ethyl ether is rarely used nowadays. With using heptane the bubble increases only half as much as with using ethyl ether. |
Application As the zero unit of all kinds of water levels, inclinometers, surveying equipment and scientific instruments. |
Temperature Range From -35 degress to approx. +55 degrees (Celsius) without impact to the spirit level, but with limited readability on the marginal areas. |
Advantages relatively simple, temporally invariable, economical |
Disadvantages strongly temperature dependent, fragile under certain circumstances |
German Standard DIN 877 reference scales DIN 1916 circular levels (for scales) DIN 2276 tubular levels for reference scales DIN 2277 circular levels, terms, explanations DIN 18722 tubular levels for geodesic instruments |