Stanford Research Systems RGA100, Operating Manual And Programming Reference

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Appendix C
SRS Residual Gas Analyzer
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Who should consider the PPM100?
i
RGA users who require auxiliary Analog I/O capabilities.
Process vacuum applications often require monitoring analog signals from multiple electronic sources
such as capacitance manometers, third-party gauges with analog outputs, mass flow controllers, turbo
pump controllers, thermometers, etc. The PPM100 analog input ports provide the simplest way to collect
and log data from up to four auxiliary vacuum instruments in parallel with its RGA partial pressure
readings.
PPM100 can also provide Analog OUT signals linked to partial pressures of individual gases for
applications requiring feedback-loop control of gas composition. Use analog OUT signals to control
auxiliary vacuum equipment such as heaters, actuators, ion sources, programmable logic controllers and
dosing valves and throttles.
Note! Analog I/O is not supported by the RGA Windows software provided with the SRS RGA.
A good example of a vacuum application requiring multiple inputs is the Temperature Programmed
Desorption (TPD) procedures that are common during surface science experiments. The only viable
alternative to the Analog I/O capabilities of the PPM100 would be to interface the RGA directly to a
personal computer, fitted with an ““A/D and D/A”” board and to write specialized software to integrate the
RGA readings with the analog I/O signals of interest.
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RGA users who need Process Control Capabilities.
PPM100 provides one of the simplest and most reliable ways to build process control and interlocking
capabilities into a vacuum system setup. Use the 8 channels of process control to make mission-critical
decisions based on (1) logic levels, (2) analog signal levels, (3) time, (4) system status, and/or (5) partial
pressure readings during your process. All this without any need for computer programming/interfacing
or additional hardware.
The only viable alternative to the Process Control capabilities of the PPM100 would be to interface the
RGA directly to a computer, fitted with a ““Logic I/O and Relay”” board and to write specialized software
to link the RGA and analog readings to the Logic and Relay ports.
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RGA Users who perform repetitive vacuum processes.
PPM100 is ideally suited for repetitive processes where the partial pressure limits and intelocking
requirements during execution of the vacuum procedure are well understood. Fast response, reliability
and standalone operation make the PPM100 an ideal alternative to the PC/RGA Windows interface.
Alarms can immediately announce out-of-range conditions for critical gas components of a gas mixture,
while process control channels and rules can be used to protect the system from catastrophic events
without any need for human intervention.
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RGA Users with high reliability requirements
The reliability of the PPM100 as a partial pressure monitor/controller far exceeds any PC Computer/RGA
Windows based setup. As a standalone instrument, PPM100 continues to collect data day-in and day-out
without interruption, without sharing CPU time with any other software applications and without being
susceptible to PC operating system crashes.