Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Programming the RGA Head 6-23
SRS Residual Gas Analyzer
Total Pressure measurement programming tips
x
Use the TP query command to check the total pressure with the FC prior to turning
on the CDEM
. Do not turn on the CDEM if the pressure is too high! See the
CDEM Handling and Care recommendations, in the RGA Maintenance chapter, for
details.
x
There is no query for the TP_Flag value. If the status of the flag is unknown prior to
requesting a Total Pressure measurement, use TP1 to set the flag or TP0 to clear it as
needed.
x
TP_Flag is cleared whenever the CDEM is turned on to protect the multiplier from
large ion currents. TP1 can be used to reset the
TP_Flag to one after making sure
the total pressure is in a ““safe”” range for the CDEM.
x
The sensitivity of the RGA for total pressure measurements will usually be affected
after mass axis recalibrations (i.e. Peak Tuning). Check the sensitivity calibration
after any peak tuning procedure.
Storing information in the RGA Head
In order to make the RGA a stand-alone mass spectrometer, four parameter storage
commands can be used to store head-specific information in the instrument’’s non-volatile
memory.
The head specific parameter values that can be stored are:
SP: Sensitivity factor for partial pressure measurements, generally for nitrogen or
argon. See SP command.
ST: Sensitivity factor for Total Pressure measurement, generally for nitrogen or
argon. See ST command.
MV: CDEM High Voltage setting that corresponds to the gain stored by MG. See MV
command.
MG: CDEM gain at the HV setting stored in MV. See MG command.
See the Parameter Storage commands list in the next section for details.
Important:
x
The Parameter Storage commands are used by the RGA Windows software to store
and retrieve the partial and total pressure sensitivity factors, and the gain and voltage
settings of the CDEM calculated and used by the program.
x
The parameter values are not used internally by the RGA to correct for sensitivity or
gain, they are simply stored so they can be read and used by any computer connected
to the RGA Head.