Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Scan and Measurement Commands 6-49
SRS Residual Gas Analyzer
The ion current is expressed in the usual format: 4 byte long, 2's complement
integer in units of 10
-16
A, with Least Significant Byte transmitted first.
Important:
x
During a Single Mass Measurement the RGA performs a ““ Miniscan”” around
the mass requested, and the maximum current value measured is sent out
over RS232 . The scanning procedure, referred to as Peak-Locking , is
designed to measure peak currents for individual masses in a mass spectrum
without being affected by drifts in the mass-axis calibration. The Miniscan
covers a 0.6 amu range centered at the mass requested, and selects the
maximum current from 7 individual measurements performed at 0.1 amu
mass increments.
x
The detector settings (i.e. type of detector and noise-floor setting) to be used
during the measurement must be selected in advance with the NF and HV
commands, otherwise, the measurements are performed with the detector
settings at the time the scan is triggered.
x
The ion detector can be zeroed, prior to the measurements, performing an
analog or histogram scan or using the CA command, under the same detector
settings. (An offset-correction factor is calculated and stored in memory that
it is then automatically used by the Miniscan procedure to correct all ion
currents measured). The CA command will also update the internal scan
parameters to assure that the correct RF levels (i.e. as specified by the last
Peak Tuning procedure) are programmed on the RF rods as a function of
mass during the Miniscan.
Parameters:
MR0: The RF/DC voltages are completely shut down and no measurement is
performed (no ion current is transmitted back to the host computer).
Use this command format at the end of a set of single mass measurements to
make sure the RF/DC are completely turned off.
MRparam, param:1 - M_MAX : A Miniscan is performed around the mass
number selected by the parameter and the maximum ion current is sent out over
RS232.
The upper mass limit depends on the SRS RGA model number: M_MAX=100
for RGA100, 200 for RGA200 and 300 for the RGA300.
Error Checking:
The command does not accept query or default parameters.
Programming tips:
x
Single mass measurements are commonly performed in sets where several
different masses are monitored sequencially and in a merry-go-round
fashion. For best accuracy of results, it is best to perform the consecutive