Les instruments du calcul savant > Instruments d'intégration conservés au musée des arts et métiers

Polar Planimeter for Demonstration

Polar planimeter for demonstration purpose
Maker: A. Gavard (Paris?); instrument no.: none; 1880
Inventory: CNAM, inventory no. 09513-0000-
Details: Bought 1880; signed »Planimètre Amsler« (see file). Tracer arm length about 1 m, for illustration and probably also for demonstration purposes.
References: Amsler 1856; Cat. CNAM 1905, 156, Cat. CNAM 1942, 128

Polar planimeter for demonstration, CNAM 09513-0000-

As already mentioned (see CNAM 08236-0000-), the physical dimension of the polar planimeter may readily be adapted for all purposes without restricting the functionality of the instrument (this would have been very difficult with orthogonal planimeters). Consequently large size demonstration models could be considered, which made it possible to let visitors of, say, a sales exhibition or a museum try out and watch the functioning of a robust large size version of a polar planimeter. The model shown was bought by the CNAM in 1880; it is plausible to think that it was ordered from A. Gavard with the intention to have such a robust model available in the museum's showrooms.

In contrast to most of the other demonstration planimeters known, this one is quite unusual in that it was executed as a nice and careful replica of a contemporary Amsler polar planimeter, in a scale of about 5 : 1. (Usually, demonstration planimeters were executed only with regard to robustness, and were limited to showing simply the main parts of such a device.)

Another remark is in order here. Polar and/or linear planimeters in sizes comparable to this demonstration model were not limited to exhibitions and/or museums. Measuring leather and hides is an application where areas up to 3 x 2 m² have to be measured, and therefore planimeters of corresponding size have to be used. They are based on exactly the same principles as their smaller counterparts; it seems, however, that planimeters of this size and for this purpose only appear rather late, i.e. e. around 1904/05. This holds for the patent references as well as for instruments known, and may be traced to the fact that only around that time the valuation of hides by their size was internationally introduced.

Polar planimeter for demonstration, detail