Stanford Research Systems RGA100, Operating Manual And Programming Reference

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6-58 Mass Filter Control Commands
SRS Residual Gas Analyzer
Mass Filter Control Commands
MLparam, param: 0.0000 - M_MAX
Description : Mass Lock
Echo : none
Activate the quadrupole mass filter (QMF) and center its pass-band at the mass
value specified by the parameter. The QMF is parked at the mass requested but
no ion current measurements take place.
The parameter is a real number and the mass increments are limited to a
minimum value of 1/256 amu.
The command excecution 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. The firmware stabilizes the voltage output of the RF Driver’’s controller
against temperature fluctuations. The 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.
Parameters:
ML0.0000: The RF/DC voltages are completely turned off.
MLparam, param: 0.0040 - M_MAX: The parameter represents the mass
setting for the QMF in amu units. The minimum mass increment value is 1/256
amu.
The upper mass limit depends on the RGA model number: M_MAX=100 for
RGA100, 200 for RGA200 and 300 for RGA300.
Error checking:
Parameters must be numbers within the specified range.
The absence of a parameter (i.e. ML ) generates a bad parameter error .