Abstract: Method and apparatus for the optical determination of the temperature of a gaseous mixture, the method comprising the stages consisting:of exciting in the infrared range the molecules of a gas of said mixture, from a first vibrational level towards a second vibrational level;of allowing the rotational relaxation of said molecules between the different rotational sub-levels of said second vibrational level;of measuring the ratio of the populations of molecules located at two of said rotational sub-levels; andof deducing from said ratio the temperature of the gaseous mixture.

Abstract: A microgyrometer for detecting a rotation about a first direction comprises a plate that is orthogonal to the first direction, suspended to a fixed frame and excited at its resonance frequency along a second direction perpendicular to the first direction. A rotation about the first direction causes the plate to vibrate about a third direction orthogonal to the first two directions. The plate comprises teeth extending respectively along the second and third directions and engaging, without contact, in grooves integral with the frame. Each tooth carries lateral metallizations which constitute capacitors with facing metallizations of the grooves.

Abstract: A resonator microaccelerometer sensitive to accelerations along a first direction is formed from a thin plate whose plane comprises the first direction and a second direction perpendicular to the first direction and that is orthogonal with a third direction. The microaccelerometer comprises a fixed frame; a seismic mass; two hanging legs; and two resonator beams. The hanging legs extend substantially along the second direction, each leg being directed toward the center of gravity of the mass, symmetrically with respect to this center; the resonator beams are parallel, but non collinear, and are symmetrical with respect to the center of gravity of the mass.

Abstract: A method for the optical determination of the pressure of a gaseous mixture includes the steps of exciting in the infrared range the molecules of a gas of the mixture, from a first vibrational level towards a second vibrational level, measuring the duration of the fluorescence of a line of the emission spectrum of the gas from one of the rotational sub-levels of the second vibrational level towards another rotational sub-level of a third vibrational level, and deducing from the duration the pressure of the gaseous mixture.

Abstract: An electrostatically servo-controlled pendular micro-sensor includes a pendular element disposed so as to respond to a force representative of a physical quantity to be measured. To avoid the drifts affecting the stability of the micro-sensor, generated by the existence of unstable parasitic voltages that impair the voltages provided by a system servo-controlling the pendular element, the electrostatic forces generated to draw back the pendular element through servo-control voltages have a zero mean value. The control voltages are periodic voltages or series of electric signals of equal durations, each having, preferably, a zero mean value.

Abstract: A method is disclosed for an optical remote measurement of the air temperature at a distance by laser excitation, in which, by means of a laser generator and by excitation of energy band transitions in the Schumann-Runge band of molecular oxygen, fluorescence of the oxygen is caused, the intensities of the fluorescence induced in two different bands are measured, the ratio of these intensities is determined and the temperature is derived therefrom wherein, on a section of appreciable depth, two absorption spectral lines are excited which at least overlap and which belong respectively to two different Schumann-Runge oxygen bands and the emission spectral line of the laser generator has a very small width with respect to that of the absorption spectral lines and its central frequency is adjusted to be substantially close to the maxima of the two absorption spectral lines.

Abstract: A method is disclosed for the optical remote measurement of the pressure of the air at a distance by laser excitation in which backscattered radiation is caused by means of a laser generator with very fine spectral line and by excitation of an absorption spectral line of molecular oxygen, the backscattered energies are measured at two different distances, the ratio of these energies is determined, a coefficient of absorption is derived therefrom depending on the temperature and the molecular density of oxygen and the density and so the pressure are calculated. An absorption spectral line is excited belonging to a Schumann-Runge band of molecular oxygen and the absorption spectral line is very wide with respect to the Rayleigh diffusion spectrum.

Abstract: An accelerometer is provided comprising an inertial mass connected to a support by means of a hinge and a vibrating element whose ends are respectively fixed to the inertial mass and to the support. The hinge is disposed in the median plane of the vibrating element and the centers of gravity of the vibrating element and of the inertial mass are merged. The effects of internal thermal stresses, which vitiate the results, are considerably reduced.

Abstract: The invention provides a string resonator vibrating under flexion whose oscillation is maintained by piezoelectric, electrostatic or magnetic exitation means.Decoupling is obtained by inertia masses which oscillate in the vibration plane of the string, between the string and fixing supports, with a movement of rotation about an axis orthogonal to the vibration plane of the string and at the level of flexible elements. The resonator is easy to manufacture, inexpensive and hase a good coefficient of quality. It may be used for force, pressure sensors or gyroscopes.