Patent ID: 8175822

Claim:
A method for measuring at least one of a pressure and a molar mass on a housing filled with a gas, the measuring being carried out via an acoustic sensor, the acoustic sensor comprising at least one transducer, an electric system connected to the transducer and a coupling layer for coupling the transducer to the housing, the method including the steps of: generating, using the transducer, an excitation acoustic signal that vibrates the housing and the gas in a wide frequency band; detecting, with the transducer, a response acoustic signal characteristic of the vibrations of the housing and the gas; converting, with the transducer, the response acoustic signal into the response electric signals; analyzing the response electric signals from the transducer using the electric system; measuring an amplitudes of the response electric signals resulting from the transducer in order to determine all of the resonance frequencies of the gas, the transducer, the layer and the housing; extracting at least two resonance frequencies of the gas from all of the resonance frequencies; measuring a gap between the at least two resonance frequencies of the gas; deriving, based on the gap of said gas, a celerity c of a acoustic waves in the gas; calculating the molar mass M of the gas by: M = γ ⁢ ⁢ RT c 2 where R is a constant of an ideal gas, T is a temperature and γ is a ratio of a specific heat for the ideal gas; and calculating the pressure P of the gas by using the celerity c of the acoustic waves in the gas and an integral J of a real response acoustic signal X(f) of the gas in the housing, where X(f) is a real curve J(P,c) in which the resonance frequencies of the gas appear alone and rectified, and the resonance frequencies of the transducer, the layer and the housing being removed.