US Patent 7381948 Mass spectroscope and method of calibrating the same

An ion resonance condition is corrected accurately in an ion trapping device. Measurements are repeated by alternately applying and not applying a resonance frequency voltage while spectral data is obtained continuously. Data obtained in the absence of the resonance frequency voltage is used as reference data to correct the set data of a resonance condition. As a result, calibration can be made while taking into consideration the variations in the amount of ions that are introduced into the ion trap.