Stanford Research Systems RGA100, Operating Manual And Programming Reference

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6-50 Scan and Measurement Commands
SRS Residual Gas Analyzer
mass measurements in a set with the same type of detector and at the same
noise floor (NF) setting. Fixed detector settings eliminate settling time
problems in the electrometer and in the CDEM’’s HV power supply.
x
It is good practice to perform an analog scan before triggering a long set of
measurements to assure the correct tuning (i.e. correct peak locations and
widths) of the quadrupole mass filter. Perform a complete Peak Tuning
Procedure as described in the RGA Tuning chapter of this manual if shifts in
the peak locations are observed.
x
The RF/DC voltages are left on at the end of a single mass measurement. Use
the MR0 command at the end of a set of measurements and before
quitting a program to make sure the RF/DC voltages are turned off.
SAparam, param: 10 - 25, *, ?
Description : Steps per amu of analog scan.
Echo: Query Response.
Set the number of steps excecuted per amu of analog scan. The parameter
specifies the number of steps-per-amu.
During an analog scan the quadrupole mass filter is stepped at fixed mass
increments through the mass range specified by the MI and MF commands. An
ion current is measured after each step and transmitted to the host computer over
RS232. SA programs the number of steps excecuted by the RGA per amu of
analog scan. The fixed mass-increment corresponding to each analog scan step is
equal to the inverse of the SA parameter value. Since the RGA is usually
operated at unit mass resolution throughout its available mass range, the
parameter value can also be interpreted as the approximate number of ion
currents to be collected for each mass peak in the spectrum.
Parameters:
SAparam, param: 10-25: The parameter specifies the number of steps-per-
amu desired during analog scans.
SA* : The number of points per amu value is set to its default value.
Default: 10
SA? : Query. Returns the SA parameter value currently in use by the analog
scans.
Error checking:
Number parameters must be integers and within the specified range.
The absence of a parameter (i. e. SA) is treated as an error.