| 摘要 |
PURPOSE:To enable a highly accurate display of the swept mass number in an area of a large mass number by subtracting an analog signal corresponding to a specified mass number from an output signal of a magnetic field detector before a variable amplification thereof. CONSTITUTION:The relationship between the true swept mass number and the output value of an A/D converter 8 is stored into a memory 18 in the form of a table using a known standard mass and an output signal of a magnetic field detector 4 is fed to a buffer amplifier 7 and a subtractor 12. After subtracted by an output signal of a D/A converter 16 with a subtractor 12, the output signal of the detector 4 is fed to a programmable amplifier 13 and then, to an analog switching circuit 14 after amplified. The circuit 14 to which an output signal of the amplifier 7 is fed selects and passes one of the outputs, which is fed to a converter 8 to be converted into a digital signal and then, into a signal corresponding to the mass number through an arithmetic control section 15. The control section 15 reads out a digital signal corresponding to the starting point of the area of mass number to be displayed at a high accuracy from a memory 18 to be fed to the converter 16. |
