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PPM100 Application Note www.thinkSRS.com
Do I need a PPM100 Partial
Pressure Monitor for my SRS
RGA?
Introduction ..................................................................................... 2
What is the PPM100 controller? ..................................................... 3
How does the PPM100 interface to the SRS RGA?....................... 4
What does the PPM100 controller do? .......................................... 5
Partial Pressure Monitor and Control ................................................................5
Leak Test Analysis ............................................................................................5
Mass Spec Display............................................................................................6
RGA Control .....................................................................................................7
Analog I/O Ports ................................................................................................8
Capacitance Manometer readings (CM1-4) ......................................................8
Data Logging (Charts and Tables) ....................................................................9
Vacuum Process Control.................................................................................10
Computer Interfaces (RS-232, GPIB and USB)...............................................10
Internet Access................................................................................................11
Who should consider the PPM100?............................................. 13
Do I still need RGA Windows? ..................................................... 16
PPM100 Specifications ................................................................. 17
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 2
Introduction
If you are planning to purchase an SRS RGA, or even if you already own one,
you might want to consider the addition of a PPM100 Partial Pressure Monitor to
your vacuum setup.
The PPM100 was designed based on recommendations from vacuum users with
a broad range of partial pressure measurement requirements. The PPM100 is
most suitable for RGA users who ...
... require analog I/O capabilities.
... require process control capabilities.
... perform repetitive vacuum processes.
... demand high reliability (i.e. mission-critical applications.)
... need access to RGA data over the world wide web
... operate in process environments incompatible with PCs
... require uninterrupted 24/7 access to partial pressure data
... require a compact and mobile partial pressure measurement
setup.
... prefer a traditional standalone RGA controller box over a PC.
... do not wish to deal with computers, software upgrades and
system crashes
If any of the above requirements applies to you, please read the rest of this
application note to familiarize yourself with: (1) the main features and
specifications of the PPM100 controller, (2) the advantages of operating any SRS
RGA with a stand-alone PPM100 controller (i.e. as compared to a PC/RGA
Windows interface), and (3) the cases in which RGA Windows is still
recommended.
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 3
What is the PPM100 controller?
Figure 1. Front panel of the PPM100 controller with its
touchscreen/LCD display and RGA control buttons.
The PPM100 Partial Pressure Monitor is a standalone, fully-programmable,
microprocessor-based vacuum system controller that when connected to any
SRS RGA100/200/300 residual gas analyzer can continuously monitor and
display partial pressures of up to eight individual gas components. It includes a
touchscreen/LCD front-panel display, pressure vs. time and analog-scan
graphing, built-in relays for vacuum system control and several multipurpose
(analog and digital) I/O ports. RS-232, USB and GPIB computer interfaces are
standard in all controllers. An Embedded Web Server (EWS), with a standard
Ethernet connector, connects the PPM100 to the World Wide Web.
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 4
How does the PPM100 interface to
the SRS RGA?
A very important feature of the PPM100 controller is that it eliminates the
requirement to connect the SRS RGA to a host PC computer. The RGA is
instead connected directly to the PPM100 controller through its standard RGA-
RS232 serial interface port and all data is displayed on the front panel of the
controller.
Warning! PPM100 is not compatible with third-party residual gas analyzers
A menu-driven user-interface allows the PPM100 operator to easily program all
required RGA Setup parameters from the controller's front panel- i.e. no RGA
Windows software interface is required.
Note that the PPM100 is a standalone instrument - there is no need to connect
the controller itself to an external computer to access its full performance and
functionality.
Figure 2. Back panel of the PPM100 controller. Connect the
SRS RGA to the RGA RS-232 (DB-9) connector using a
standard serial communication cable.
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 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.
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 6
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.
Figure 4. Leak trend Display Mode. Use this graphical mode to
Leak test components of your vacuum system. PP2 data bar is set
to Leak trend, and three display modes are available on the same
screen to visualize leak rates during testing.
Mass Spec Display
A Scan Display mode is available to graph RGA Mass Spectra directly on the
front panel of the controller. During analog scanning the quadrupole mass
spectrometer is stepped at fixed mass increments (i.e. 0.1 amu) through a user-
specified mass range. The ion current is measured after each mass-increment
step and transmitted to the PPM100 for display. Analog scanning simplifies the
detection of mass peaks for component gas identification, and provides a direct
measure of the mass resolution of the quadrupole mass spectrometer.
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 7
Figure 5. The Mass Spec Display mode of the PPM100 shows
complete RGA Mass spectra and includes a cursor for fast peak
identification.
RGA Control
The PPM100 includes a FILAMENT button on its front panel for manual
activation of filament emission as required for partial pressure measurements.
Press the E. MULTIPLIER button at any time to activate the electron multiplier
detector during analog scans. All RGA ionizer settings are easily configured from
the touchscreen/LCD user interface.
Figure 6. RGA Setup parameters are easily set from the front
panel.
Stanford Research Systems (408)744-9040
www.thinkSRS.com
PPM100 Application Note 8
Analog I/O Ports
The PPM100 controller has four analog input/output ports. Their range is