Maker

Carl Zeiss (Oberkochen)

Model

Ni2

Serial Number

16809

Dimensions

268 x 125 x 125 mm

Image

Description

The Zeiss Ni2 was the first commercially available automatic level, released about 1950. (A pendulum 'compensator' replaces the tilting tubular level and the tilting screw of the earlier 'tilting levels'. After setting a circular level (viewed horizontally through a 90° prism), the line of sight is made horizontal by the compensator in the optical path. Since no tubular level must be set for each staff reading, the speed of levelling is doubled in comparison with the earlier spirit levelling.

The telescope features an upright image and a 40 mm diameter objective lens. The focussing knob has a combined coarse-fine function: After changing the sense of rotation, the fine motion is active. The motion about the vertical axis has a friction coupling (no locking screw) with a fine motion screw (left and right handed).

The levelling precision depends on the staff and additional equipment used. With a plane parallel micrometer attachment and (5mm or 10 mm) invar line scale staffs, a 1 km double run precision of ±0.3 mm is achievable.

The compensator has a setting acuracy of ±0.2" and features air damping. Height of Ni2 = 130 mm, diameter of base = 130 mm, weight of instrument (with horizontal circle = 2.4 kg, without 2.1 kg. Minimum focussing range 3.3 m.

All automatic levels feature particular instrumental errors such as the obliquity of horizon and, possibly, a susceptibility to magnetic fields (incl. that of the Earth). A number of techniques are available to overcome the former effect.

History & comments

Was purchased (new) by UNSW

Conservation

In wooden box, 330 x 160 x 190 mm (box 2.9-3.0 kg)

Condition

Good condition and in working order. Glue marks on outside of level.

Remarks

Catalogued by JMR, Photo by JMR

See 0309 for autocollimation attachment.

See 0311 for 90° objective prism attachment.

Dates

Catalogued in 2000