Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Programming the RGA Head 6-25
SRS Residual Gas Analyzer
QMF Programming tips
x
Take advantage of the stabilization feature of the ML command whenever possible.
For example: Do not send any new commands to the RGA Head once the QMF has
been set to the specified mass value, or otherwise recall the ML command, whenever
practical, to refresh the QMF RF/DC settings.
x
A typical application of the ML command involves monitoring a single mass
concentration looking directly at the linear output of the CDEM anode with a boxcar
or transient digitizer.
x
Use the ML0 command to turn off the RF/DC bias when finished performing
measurements and before quitting the program controlling the RGA.
x
It is good practice to perform an analog scan before using the ML command 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.
Error Checking the RGA
Several firmware-driven checks automatically test the RGA when the unit is turned on,
and continuously monitor the internal workings of the instrument. A ““Background
Filament Protection Mode”” is activated when the filament is turned on to protect the
delicate filament (and CDEM) from accidental overpressures. Several commands can be
used to trigger hardware tests on the ECU. Any one of the internal checks just described
can detect and report errors, and it is the responsibility of the user to constantly monitor
the RGA Head for error reports.
There are two ways to detect the presence of errors in the RGA:
1. Visually : Inspecting the red LED’’s on the rear panel of the ECU.
The Error LED is turned on whenever a hardware problem is detected, and it flashes
twice if a communications error is generated during programming.
The Burnt and Leak LED’’s indicate specific filament problems and are turned on, in
addition to the Error LED, whenever the ionizer’’s emission is internally shut down or
not established as requested.
2. Error Queries : Queering the Error Bytes with the Error Reporting commands.
The ““Error Byte Definitions”” section of this chapter describes the different error
bytes used to store the results of the internal checks. The ““Error Reporting
Commands”” query the error bytes and are used to quickly diagnose problems.
Important : The RGA Windows software supports all the Error Reporting commands
and routinely monitors the Error Bytes. Detected errors are immediately reported to the
user and identified based on Error Codes. See the RGA Troubleshooting chapter for
recommended solutions to the problems.
The STATUS error byte is the gateway to error diagnosis: