Disk planimeter

 © Technisches Museum Wien, Photo: Peter Sedlaczek
Collection Area
Technical and Scientific Principles
Calculating, Drawing & Design Instruments
At the moment this object is not published in the museum.

Who wants to measure areas by counting squares on graph paper? The planimeter does this mechanically.

A planimeter is an analogue mathematical calculator. By running it around the perimeter, it is used to determine the size of a surface. The extent of the surface is scanned using a point fastened to an arm. This moves the slides and the arm of the planimeter.

The movement of the arm is transmitted through a tension cord to the large, horizontal disk, which then also starts to move. Due to friction, the wheel with the embossed scale starts to turn on the disk. The small, horizontal wheel just counts entire revolutions of the other wheel. Once back at the starting point of the perimeter, the size of the surface can be read off from the scales of the two small wheels.
The theoretical basis for this is infinitesimal calculus, particularly Green's Theorem.

Manufacturer: Starke & Kammerer, Vienna
Date of construction: around 1895

Inv.Nr. 18843/1

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