Functional Description
'JOOJHBO-52
___________________________________________________________________ MS Detector
_______________________ Finnigan LTQ Hardware Manual _____________________
2-35
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System Control and Monitoring Circuitry
The LTQ electronics contains the following circuits for controlling and
monitoring the operation of the MS detector:
• Dc voltage control circuitry
• Divert/inject valve control circuit
• API source control circuit
• Electron multiplier control circuit
• Conversion dynode control circuit
• Ion transfer capillary heater/sensor control circuit
• APCI vaporizer heater/sensor control circuit/safety interlock relay
• Ion gauge control circuit
• Convectron
®
gauge control circuit
• Vacuum protection circuitry
• RF voltage control circuitry
• Temperature monitoring circuitry
• Diagnostic circuitry
The dc voltage control circuitry controls and monitors the dc voltages that are
applied to the ion transfer capillary heater, tube lens, ion optics, lenses, and
mass analyzer electrodes.
The divert/inject valve control circuit controls and monitors the divert/inject
valve.
The API source control circuit controls and monitors the high voltage that is
applied to the ESI needle, the APCI corona discharge needle, and the NSI
capillary.
The electron multiplier control circuit sends a signal to the electron
multiplier power supply that is proportional to the voltage to be applied to the
electron multiplier cathode. It also reads back a signal that is proportional to
the actual voltage applied to the electron multiplier cathode. The electron
multiplier control circuit lowers the electron multiplier voltage when mass
analysis is not occurring.
The conversion dynode control circuit controls and monitors the polarity of
the 15 kV potential that is applied to the conversion dynode.
The ion transfer capillary heater/sensor control circuit monitors the
temperature of the ion transfer capillary via a platinum probe temperature
sensor. It also provides the voltage needed by the ion transfer capillary heater.
The APCI vaporizer heater/sensor control circuit controls the temperature of
the APCI vaporizer via a thermocouple sensor. It also provides 230 V ac line
voltage to the heater in the APCI vaporizer.
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