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A332-26 · Aneroid
c.1965
Object Overview
This Modernist Weather Station was manufactured around 1965 by the German company Arthur J. Förster of Karl-Marx-Stadt (now Chemnitz), one of Germany's well-known manufacturers of meteorological and measuring instruments during the 20th century. The instrument is a wall-mounted domestic weather station combining an aneroid barometer and a mercury thermometer within a single wooden case. Its restrained geometric design, combination of natural wood with gold-toned metal components, and carefully considered arrangement of the measuring scales reflect the characteristic features of mid-20th-century European industrial design.
The barometer's case takes the form of a substantial rectangular wooden panel with smooth, flat surfaces and straight edges. The absence of decorative carving, moulded cornices, and other traditional ornamentation emphasises the simplicity and functionality of its construction. The case is presumably made from a light-coloured wood, probably beech, with a decorative walnut veneer on the front. This combination of materials is consistent with Förster's manufacturing practices, as the company used wooden bases with various types of decorative veneer, including walnut, for its instruments.
aneroid capsule tensioned on a C-spring
aluminium, brass, glass, plastic, steel, wood
The front surface has a warm golden-brown tone with a distinctive yet restrained wood grain. Fine longitudinal lines alternate with darker, slightly undulating areas, forming a natural, irregular pattern. The grain is particularly visible on the exposed sections of the panel between the barometer and thermometer, as well as along its upper and lower edges. Over time, the exposed surfaces have acquired a lighter, honey-brown colour and a considerably less contrasting grain appearance compared with the original shade preserved beneath the thermometer and dial. All wooden surfaces are coated with a clear protective varnish, giving them a soft sheen and emphasising their natural texture.
On the rear of the case is a circular cover made of light-coloured plastic, secured by several screws. The cover protects the sensitive mechanism from accidental mechanical damage, dust, and foreign objects. The movement itself is attached to the inside of this cover by screws. A small metal hanging bracket with a serrated opening is fitted to the upper part of the rear panel, allowing the instrument to be mounted on a wall.
The main part of the front panel is occupied by a square barometer dial made from a thin sheet of aluminium painted in a pale golden-cream colour. Its surface has a fine-grained matte texture, with graduations, numerical markings, and weather inscriptions printed in black. The dial features two concentric barometric scales: an inner scale graduated in millibars (mbar) and an outer scale expressed in torr (Torr), practically equivalent to millimetres of mercury. The inner scale covers approximately 940–1060 mbar, while the outer scale extends from 700 to 790 Torr.
The use of two units of measurement reflects a transitional period in European meteorological practice, when traditional units based on the height of a mercury column were gradually giving way to metric units of pressure. A millibar is one thousandth of a bar and is equivalent to 100 pascals. The torr, named after the Italian physicist Evangelista Torricelli, is historically associated with the measurement of atmospheric pressure using a mercury barometer. According to its modern definition, 1 torr equals 1/760 of a standard atmosphere, or approximately 133.322 pascals. The millimetre of mercury likewise represents the pressure corresponding to a specified height of a mercury column under defined physical conditions. In practical barometric measurements, these units are numerically almost identical, although a very small difference exists between them in strict metrological terms.
Both scales share a common centre and correspond to the same angular position of the indicating hand, allowing atmospheric pressure to be read directly in either unit.
Inside the measuring scales are traditional weather indications in Dutch: REGEN (rain), VERANDERLIJK (changeable weather), and MOOI (fine weather). These inscriptions suggest that this particular example was intended for export to the Netherlands or the Dutch-speaking part of Belgium. Such weather indications are characteristic of domestic barometers and serve as an approximate guide linking atmospheric pressure to likely weather conditions. However, absolute pressure readings alone cannot reliably predict the weather: the pattern of pressure changes over time is considerably more informative.
The dial is protected by a square convex mineral glass fitted into a substantial brass bezel with rounded corners. The bezel has a stepped profile, a polished golden surface, and is secured to the case by four screws positioned at its corners. Its distinctive geometry gives the instrument a characteristic appearance and emphasises the square shape of the measuring scale.
Surrounding the dial, beneath the protective glass, is a painted aluminium frame that serves both as a reflector ring and as a spacer supporting the glass. It creates a light-coloured inner border, improves the visual appearance of the scale, and provides the necessary clearance between the dial surface and the inside of the glass, allowing the indicating hand to rotate freely without coming into contact with the protective glass.
An additional brass pressure-trend pointer is mounted at the centre of the protective glass. It is operated manually by means of a small circular knurled knob located on the outside of the glass. This pointer is not mechanically connected to the aneroid movement and is intended to mark the previous position of the main hand. By aligning it with the current barometer reading, the user can later determine the direction and approximate magnitude of any pressure change. This simple device transforms the instrument from an ordinary atmospheric pressure indicator into a basic means of monitoring pressure trends.
To the right of the barometer is a vertical mercury thermometer mounted on a narrow rectangular plastic plate with a warm golden finish. A temperature scale in degrees Celsius, covering the range from 0 to +40 °C, is printed in black on its surface. The upper part of the scale bears the symbol °C, while the plate itself has slightly rounded ends and is secured by two brass screws. The thermometer's glass capillary is positioned along the central axis of the scale, with a small mercury reservoir at its lower end. As the temperature changes, the thermal expansion or contraction of the mercury causes a corresponding movement of the mercury column within the capillary, allowing the ambient temperature to be read directly.
Of particular interest is the internal aneroid movement, characteristic of those produced by Fischer, a company that also specialised in the manufacture of barometric measuring systems. Its construction is based on a circular corrugated evacuated metal capsule, whose deformation is converted by a system of levers into the angular movement of the indicating hand.
The sensing element consists of a single aneroid capsule with concentric corrugations that provide the necessary elasticity of its diaphragms. As atmospheric pressure increases, the capsule contracts; as pressure decreases, it expands. Since the internal pressure of the capsule is considerably lower than atmospheric pressure, the resulting pressure difference produces a small but measurable change in its height.
The capsule is mechanically connected to a powerful, pre-curved brass leaf spring, which provides an opposing force and establishes the necessary operating conditions for the sensing element. The spring has a characteristic broad, ribbon-like form and is secured to the supporting structure of the movement. Its elastic deformation accompanies the movement of the capsule and contributes to the mechanical response characteristics of the system.
Further transmission of motion is accomplished by a main lever extending from the leaf spring and terminating in a substantial rounded contact projection that acts as a pressure shoe. This projection rests freely on a small platform of a pivoting bell-crank lever, without forming a rigid articulated connection. This arrangement allows force to be transmitted through direct contact between the components while preserving a degree of freedom in their relative movement and reducing the influence of additional mechanical connections on the sensing element.
The bell-crank lever rotates about its own pivot and has two functional arms. The first carries the contact platform that receives the movement of the main lever, while the second, oriented approximately vertically, transmits motion to the pointer spindle. As the height of the aneroid capsule changes, the main lever shifts its position, acting on the contact platform and producing a small rotation of the bell-crank lever.
A thin, flexible cord extends from the vertical arm of the bell-crank lever to the pointer spindle, forming a simple system for converting the displacement of the lever into rotary motion. Depending on the direction of the lever's movement, the cord winds onto or unwinds from the pointer spindle, causing the indicating hand to rotate accordingly across the barometric scale. Owing to the small radius of the pointer spindle, even a slight displacement of the lever system is converted into a comparatively large angular deflection of the hand, providing the necessary mechanical amplification.
Constant tension in the cord is maintained by a fine spiral hairspring mounted directly on the pointer spindle. It produces a preloaded torque acting in opposition to the force of the tensioned cord, preventing slack and ensuring continuous contact between the components of the transmission system. As atmospheric pressure changes, the position of the hand is determined by the balance of forces generated by the aneroid capsule, the main leaf spring, and the hairspring on the pointer spindle.
The movement is mounted on a metal supporting plate of a distinctive open-sided design, providing access to its principal components. The construction also incorporates adjustment elements that allow the initial position of the sensing system to be corrected and the hand's indication to be calibrated against the actual atmospheric pressure. Despite its relatively small number of components, the movement represents a carefully conceived combination of elastic elements, contact levers, and a cord transmission system, capable of converting microscopic deformations of the aneroid capsule into a clearly visible movement of the indicating hand.
Overall, this Arthur J. Förster domestic aneroid barometer is a characteristic example of German instrument-making from the mid-1960s, combining traditional aneroid measuring technology with the functional design of the post-war era. The natural wood of its case, restrained geometric forms, golden metal fittings, and dual barometric scale give the instrument a distinctive appearance, while its mechanical system demonstrates a rational approach to the construction of compact and sufficiently accurate domestic barometers.