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