Patent ID: 7331216

Claim:
A method for leak rate measurement of a gas to be detected having a specific molecular mass, performed by use of a mass spectrometer arranged for mass-dependent deflection of gas ions, said method comprising the steps of: measuring a current generated by the ions impinging on an ion catcher of the mass spectrometer; evaluating a current signal corresponding to the respective current intensity; superposing the current signal corresponding to a specific mass with current signals of adjacent masses; and modulating at least one influencing quantity of the mass spectrometer influencing the deflection about a point of highest sensitivity for the mass thereby to be detected, in order to separate the current signal of the mass to be detected from the current signal of the adjacent masses by evaluating at least one frequency portion, wherein the modulation depth is restricted to the peak region of a current signal in which the extension of the influence of adjacent masses has a substantially linear course.