type 2A aneroid barometer
Datemid 20th-late 20th Century
Inventory Number2003-1-0120
ClassificationBarometer
Subject
Maker
Thommen A.G. Precision Instruments and Avionics
founded 1936
Cultural Region
Place of Origin
Dimensions12.2 × 10.1 × 11.5 cm (4 13/16 × 4 × 4 1/2 in.)
Material
DescriptionCircular aneroid barometer mounted in a rectangular metal case. The case has a gray-green enamel finish, with a metal latch at the front, and a leather strap. On the inside lid of the case, there is a black square lable with the maker's information, as well as a conversion table for mb, mm Hg (Tor.) and kg/m ^3, in white lettering. There are three black screws, and one larger silvered screw placed outside the black edging around the barometer in the backing of the case, and one smaller silvered screw inside the black edging around the barometer. On the face of the barometer there is a scale in mb from 0-100, as well as another, semi-circular scale from 500-1100, inside the first. One needle points to each graph.
Conversion table on inside case:
First row: mb / mm Hg(Tor.) / kg/m^3
Second Row: 1 100 / 0,75006 75,006 / 10,1972 1019,72
Third Row: 1,33322 133,322 / 1 100 / 13, 5951 1359,51
Fourth Row: 0,0980665 9,80665 / 0,0073556 7,3556 / 1 100
Scales:
Millibar / Druck [pressure]
millibar scale: 0-90
iniside scale: 500-1100
Conversion table on inside case:
First row: mb / mm Hg(Tor.) / kg/m^3
Second Row: 1 100 / 0,75006 75,006 / 10,1972 1019,72
Third Row: 1,33322 133,322 / 1 100 / 13, 5951 1359,51
Fourth Row: 0,0980665 9,80665 / 0,0073556 7,3556 / 1 100
Scales:
Millibar / Druck [pressure]
millibar scale: 0-90
iniside scale: 500-1100
Signedinside cover: Thommen S. A. Waldenbourg. Suisse; on dial face: Thommen A. G. / Waldenburg; on barometer dial: Thommen A. G. / Waldenburg / Type 2A
Inscribedon top of case: BAROMETER;on inside top of case: Thommen S. A. Waldenbourg. Suisse. / Type: [white rectangle] Fabr. No. [white rectangle] / DIN 1314
FunctionAneroid barometers are used to measure atmoshperic pressure and altitude. They hold, a small, partially evacuated and flexible metal capsule inside the casing, which is kept from collapsing by a small spring. This capsule contracts and expands in accordance with the surrounding air pressure. The minute changes in the volume of the capsule are translated through internal clockwork to the dial on the face of the barometer, and can be read against the accompanying scales.
In this particular Thommer barometer, the combination of a wide-ranging scale for the inner dial, and a very precise scale for the outer dial, allows this instrument to be used in various fields either to measure changes in atmospheric pressure (meteorology), or altitude geodetics, avionics). Its portable casing is designed for use in the field.
In this particular Thommer barometer, the combination of a wide-ranging scale for the inner dial, and a very precise scale for the outer dial, allows this instrument to be used in various fields either to measure changes in atmospheric pressure (meteorology), or altitude geodetics, avionics). Its portable casing is designed for use in the field.
Davis & Son
Date: 1843-1873
Accessories: small metal key
Object number: 1998-1-0606
C. F. Casella & Co. Ltd.
Date: circa 1920
Accessories: Card and tags indicate there should be a leather carrying case, strap, and 3 legs for support. However, this instrument has been stored by itself.
Object number: DW0642
Western Electric Company
Date: before 1933
Accessories: cords missing
Object number: RS0153
William Hamilton Shortt
Date: circa 1929
Object number: 1998-1-0187a
