Hardware manual

6-22 Agilent 7500 Series ICP-MS Hardware Manual
6 Technical Information
accumulated by the accumulator. The accumulated value is then converted to
pulse counts by the P/A factor (Figure 136). They are generally called dual
mode.
For adjustment of the dual mode, a P/A factor must be set.
When data acquisition starts, the Smart Card and the CPU board
automatically select which masses are analyzed by the pulse mode and by the
analog mode; the switching level is about 1 x 10
6
cps. If the signal is exceed the
EM limit value, this mass will be skipped automatically.
When the EM mode is set to AUTO in method and the signal exceeds the
threshold of the pulse protection, the pulse mode protection works and the
signal is measured by analog mode only. If the high signals, which cannot be
measured even by analog mode, are entered, this mass will be skipped
automatically to prevent the EM. After finishing data acquisition, the data is
transferred to the MassHunter Workstation (or ChemStation) for analysis.
The lifetime of the EM is determined by the EM voltage (Analog HV and Pulse
HV) after adjusting the voltage of the EM. The EM will need replacing when the
Analog HV reaches about 3300 V or the Pulse HV reaches about 1800 V after
adjusting the EM voltage.
Figure 136 Ion Detection System
Ions
Electron Multipiler (EM)
+ HV
- HV
Pre-amp
Pre-amp
Discrimi-
nator
Counter
Anti-log
Logic
Accumu-
lator
MassHunter Workstation
(or ChemStation)
MassHunter Workstation
(or ChemStation)