Stanford Research Systems RGA100, Operating Manual And Programming Reference

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6-66 Tuning Commands
SRS Residual Gas Analyzer
Warning: Please read the Peak Tuning Section of the RGA Tuning Chapter before using
this command.
Program the output of the RF_Driver @ 0 amu during a Peak Posion Tuning Procedure.
The parameter (one of four peak tuning parameters) represents the voltage output selected
for the RF_Driver @ 0 amu, in mV.
The magnitude of the RF determines the mass-to-charge ratio of the ions that can pass
through a quadrupole mass filter without striking the rods (i.e with stable oscillations). A
linear relationship between mass and RF amplitude is one of the most attractive features
of these type of filters.
The regulated output of the RF source that powers the RGA’’s quadrupole rods is
controlled by, and linearly related to, the voltage output of an RF_Driver circuit. A linear
relation exists between the output of the RF_Driver, the RF amplitude on the rods, and
the mass setting of the filter. The purpose of a Peak Position Tuning Procedure is to
determine the voltages that the RF Driver must output at 0 and 128 amu so that all the
peaks in an analog spectrum appear in the right position. The RI command is used to
program the voltage output of the RF_Driver @ 0 amu during the Peak Position Tuning
Procedure. The value is saved in the non-volatile memory of the RGA Head and used by
the firmware to generate the internal scan parameters used to step the RF during scans
and single mass measurements .
Note to Supervisors : A calibration disable jumper (JP100) available on the circuit board
can be used by a supervisor to block any attempt to modify the value of the DI parameter.
Supervisors may use this feature to prevent accidental changes in the calibration
parameters by inexperienced operators. Setting JP100 will disable peak tuning of the
Head.
Parameters :
RIparam, param: -86.0000 - +86.0000: If Calibration is enabled by the JP100 jumper
(See CE Command), the parameter is saved into the non-volatile memory of the RGA
Head and the internal scan parameters used to step the RF during scans and single mass
measurements are updated accordingly.
RI* : Use this format to replace the peak tuning parameter with the original factory setting
for the RF_Driver output @ 0 amu. The factory value is retrieved from memory, and used
as the new parameter value to excecute the command as above.
RI? : Query. Returns over RS232 the parameter value currently saved in memory.
RI: Uses the current parameter value to recalculate the internal scan parameters used to
step the RF during scans and single mass measurements. This is often used to compensate
against small temperature drifts in the mass scale, caused by drifts in the output of the
RF_Driver.
Error checking:
The absence of a parameter (i. e. RI) is treated as an error in the parameter.