Irrespective of their type, all precision levels are based on long-time stabilisation and
reliability, but also on a free measuring base – the centre of the earth. Due to the grav-
itation, the liquid with embedded bubble of gas or the gravity pendulum indicates the
horizontal or vertical level based on this natural reference. Electronic inclinometers or
spirit levels measure the position of the pendulum compared to the measuring faces
fitted on the tool body.
