Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Scan and Measurement Commands 6-51
SRS Residual Gas Analyzer
SC[param], param: 0 - 255, *
Description : Analog Scan Trigger.
Echo: Ion Currents
Excecute one or multiple analog scans under the present scan conditions.
The scan parameter can be set for single, multiple and continuous scanning
operation.
Analog scanning is the most basic operation of the RGA as a quadrupole mass
spectrometer. During analog scanning the quadrupole mass spectrometer is
stepped at fixed mass increments through a pre-specified mass-range. The ion
current is measured after each mass-increment step and transmitted to the host
computer over RS232. The mass range for the scan is set in advance with the
commands MI (Initial Mass) and MF (Final Mass) and the mass-increments are
fixed with the command SA. Scan rate and detection limits are pre-programmed
by the NF (Noise Floor) setting. A current value is transmitted for MI and after
each mass increment through MF for a total of (MF-MI )*SA+1 measurements
(See AP query command).
The ion currents are represented as integers in units of 0.1 fA, and transmitted
directly in Hex format ( four byte integers with 2's complement format and Least
significant byte first).
The type of detector and noise-floor settings to be used during the scans must be
selected in advance with the NF and HV commands.
Important:
x
Any command received by the RGA in the middle of a scan will immediately
stop the scan, halt transmission and clear the RGA’’s transmit buffer.
x
The detector’’s zero and the internal scan parameters are checked and
corrected at the beginning of each scan resulting in a slight delay before the
scan actually starts.
x
A Total Pressure measurement is performed at the end of each scan and
transmitted out to the host computer (Please see AP and TP
Commands).
x
Unless otherwise specified, the measurements are performed with the
detector settings that are present at the time the scan is triggered.
Parameters:
SC : Continuous scanning mode. The RGA produces a continuous string of
analog scans.
A new command must be sent to the RGA in order to stop the scanning activity.
Once the command is received, the scan is immediately stopped, all transmission