Patent ID: 7332714

Claim:
A quadrupole mass spectrometer, comprising: an electron impact ion source in which a demarcation space is formed of at least a grid electrode and an ion focusing electrode within a vacuum system, electrons emitted from an electron emitter which is disposed outside of the grid electrode are accelerated toward the grid electrode, gas molecules flying into the demarcation space are ionized in a process that the accelerated electrons pass through the mesh of the grid electrode and then continue to oscillate to inside and outside of the grid electrode, and the ionized ions are emitted as an ion beam to outside of the demarcation space through a hole formed in the center of the ion focusing electrode; a quadrupole mass analyzing portion which separates the ion beam obtained from the ion source depending on a charge-to-mass ratio of the ions; a detector which catches an ion beam according to the mass separated through the quadrupole mass analyzing portion and converts it into an electric current signal; and a total pressure measurement electrode for examining an ion density disposed in the demarcation space which is formed of the grid electrode and the ion focusing electrode, wherein: partial pressure strength according to a gas type in the vacuum system is measured from an ion current intensity to be obtained.