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RGA Command Set 3-47
Technical Reference
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.
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:
•
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.
•
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.