Stanford Research Systems RGA100, Operating Manual And Programming Reference

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6-24 Programming the RGA Head
SRS Residual Gas Analyzer
x
MV and MG are only available in units with the CDEM option (Option 01) installed
(See MO command for details) and usually store a calibrated pair of [gain, high
voltage] values for the CDEM.
Programming example
The following list shows a typical application of the storage commands to save head
specific information in the RGA Head. The first line stores a partial pressure sensitivity
factor of .1mA/Torr, the second line stores into memory a total pressure sensitivity of
.02mA/Torr, and the last two lines store a [1400V | 10,000 gain] calibrated pair for the
CDEM.
SP0.1 Partial pressure Sensitivity= 0.1 mA/Torr.
ST.02 Total pressure Sensitivity = 0.02 mA/Torr.
MV1400 CDEM HV setting (for MG gain): 1400 V.
MG10 CDEM gain (@MV setting)=10,000x.
Programming the Quadrupole Mass Filter
Use the ML (Mass Lock) command to activate the quadrupole mass filter (QMF) and
center its pass-band at any mass number within the available range. The command ML is
included for the convenience of users who wish to use the RGA as a mass filter. The
QMF is parked at the mass requested but no actual measurements take place. The
command’’s parameter can be a real number and the step resolution is 1/256 amu.
The command execution involves two steps:
1. The RF/DC levels corresponding to the mass requested are calculated and set on the
QMF rods based on the mass axis calibration parameter values specified by the last
Peak Tuning procedure.
2. A firmware driven algorithm is then automatically enabled to stabilize the voltage
output of the RF Driver’’s controller against temperature fluctuations.
The net result is very stable RF/DC levels that are highly insensitive to the operating
conditions of the RGA Head.
Important: The RF/DC stabilization algorithm (Step 2 above) remains active as long as
no new commands are detected by the RGA Head. Once a new command is received,
stabilization stops, and the new command is executed.
Use the ML0 command to turn off the RF/DC bias when finished performing
measurements and before quitting the program controlling the RGA.
QMF programming example
ML28 Activate the mass filter and center its pass band at 28 amu
ML42.50 Activate the mass filter and center its pass band at 42.50 amu.
ML0 Deactivate the QMF. (same as MR0 command)