174 Troubleshooting and Maintenance Manual
8 Electronics
• Perform analog-to-digital conversion for the direct signal, ion source, and
mass filter temperature signals, and foreline pressure or turbo pump speed
signal.
• Monitor the signals from the vacuum system and fans and the filament
status, HV fault and RF fault signals from the quadrupole board. Activate
the shutdown line when the analyzer electronics must be disabled.
• Generate the control signals (on and off) used by the AC board for the
high-vacuum pump and calibration valve.
• Generate ± 600 and ± 300 VDC (nominal) power for main board lens
amplifiers and quadrupole board DC amplifiers.
• Supply and control the power for the ion source and quadrupole (mass
filter) heaters.
• Provide 24 VDC power for the cooling fan.
Signal amplifier board
The log amplifier board amplifies the output of the detector. It produces an
output voltage of 0 to 10 volts DC, proportional to the logarithm of the input
current of 3 picoamps to 50 microamps.
An analog-to-digital converter converts the amplifier output voltage to digital
information. The LAN/MS control card converts the data into abundance
counts proportional to the detector signal current.
AC board
The AC board is mounted on the opposite side of the electronics panel from
the LAN/MS CPU. The AC board is also sometimes called the power
distribution/vacuum control board. It performs these functions:
• Provides input voltage transparency for the MS.
• Distributes AC line power to the AC/DC power supply, the foreline pump,
and the turbo pump controller.
• Turns the calibration valve on or off as directed by the main board.
• Provides the voltage for the calibration valve.
• Provides a logic interface to turbo controller.
• Controls the foreline gauge.
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