Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Appendix C
SRS Residual Gas Analyzer
5
What does the PPM100 controller do?
Partial Pressure Monitor and Control
PPM100 can monitor and display up to eight independent RGA partial pressures on its front panel LCD.
Each partial pressure reading has its own (1) mass, (2) detector , (3) scan rate and (4) alarm settings. The
Partial Pressure Display mode of operation is primarily used to generate single gas data for leak testing
applications, and to track changes in the concentrations of up to eight independent components of a gas
mixture as a function of time. The partial pressure readings can also be linked to alarms, process control
relays and both digital and analog output signals.
Figure 3 . The partial pressure Monitor Display mode of the PPM100 shows partial
pressure readings, and alarm status, for up to eight individual gas species.
Leak Test Analysis
The PPM100 can be used to leak test components attached to the vacuum system. Use leak trend graphs
to detect leaks as partial pressure transients while spraying the vacuum system components with a tracer
gas such as helium or argon. A stamp-sized 'Signal vs. time' plot of the most recent partial pressures for
the selected mass is displayed on the front panel. A small instantaneous partial pressure reading is also
included next to the plot.
When 'Audio Leak Trend' is selected, a repetitive audio signal whose frequency is proportional to the
partial pressure readings provides a means to ““hear”” pressure transients, eliminating the need to look at
the front panel display while searching for leaks.
In order to provide optimum data acquisition rates at the mass of interest, all other partial pressure
readings and displays are disabled while in this display mode.