Wristwatches provided with a device for measuring atmospheric pressure are already known. These wristwatches conventionally include a pressure sensor, for example of the aneroid type, whose geometric dimensions vary with fluctuations in atmospheric pressure. In a known embodiment, the variation in the geometric dimensions of the pressure sensor with atmospheric pressure fluctuations is converted into a linear motion of a feeler, which in turn controls the pivoting of a lever. The pivoting motion of the lever is in turn converted into a rotational motion of a gear train which meshes with a display wheel in a drive ratio calculated such that an altitude indicator hand carried by the display wheel provides the user of the watch with a legible altitude indication.
Constructions of the type briefly described above are typically used to provide the user of the watch with an indication of the altitude of the place where he is located. It is known that the atmospheric pressure value is a function of the altitude of the place where atmospheric pressure is measured. It is also known that the altitude indication provided by the watch may be distorted because of meteorological variations. Thus, even if the user of the watch does not change location, it is possible for the watch to provide a changing indication of the altitude of that location under the effect of atmospheric pressure fluctuations.
It is therefore useful to associate a barometric device with an altimeter device. Indeed, as a result of the barometric device, it is possible to provide an indication of the local atmospheric pressure variation over time. This indication may then be used either to correct the altitude indication, or to predict the evolution of meteorological conditions.
The drawback of this type of solution lies, however, in the fact that it is difficult to envisage integrating an altimeter device combined with a barometric device in a portable object of small dimensions, such as a wristwatch.