Residual Gas Analyzer

The densely packed CCU contains all the necessary electronics for RGA probe control and for computer communications. An RS-232 COM port is used to communicate to the host computer and the baud rate can be chosen in the software. The 115,200 baud setting is normally used except with very long cables or in noisy environments. USB to COM port adapters function well on computers such as inexpensive laptops that do not have the serial COM ports. Placing the adapter at the computer end of the communication cable will free the user from the 5 meter limit on USB cable length and poor USB noise immunity. The CCU is powered by +24 VDC (2.1 A). This power may be supplied using the wall plug unit that comes with each XT unit at no extra cost. The CCU can easily be removed from the probe for high temperature bake-outs. The firmware is automatically updated with new software versions. The complete status of the probe is reported back to the computer. This status report, including the probe temperature, the CCU temperature and the voltages on the probe elements is continuously read back to the host computer and may be used for diagnostic purposes.

Long-life thoria coated iridium filaments are used for both RGA and ion gauge operation. The filament assembly is composed of two thoria coated iridium filaments, The filament supply in the CCU constantly monitors the filament resistance. When one of the filaments finally evaporates and fails, the resistance increases, warning the user to replace the filament assembly before electron emission becomes unavailable. This filament assembly is protected against vacuum excursions by both the ion and Pirani gauge functions. Because of this protection, filaments will last far longer than filaments in competitor’s RGA units. Extorr filaments are easily replaceable in the field. The replacement can be done in minutes, and for less than $100.

A Faraday cup detector is standard with 100, 200 and 300 amu systems. The ultra-sensitive, wide dynamic range amplifier detects ion currents from 10^-6 to 10^-15 Amps automatically. This allows partial pressure measurements from 10^-4 to 10^-11 Torr. This huge dynamic range means you can make measurements of small and large gas partial pressures in a single spectral scan. Since this same amplifier is used in conjunction with the electron multiplier when present, partial pressure measurements to below 10^-14 Torr are possible.

Partial pressure spectral scans, partial pressure trends, audio leak detection, true total pressure measurement, and probe operating parameter modification are all features that are standard with Extorr XT systems. The intuitive nature of the Extorr Windows® computer environment makes for rapid system utility for both the seasoned RGA user as well as for the novice. Simplicity of communication makes for easy integration into existing computer vacuum control systems.

All Extorr systems come with VacuumPlus, a real-time Windows® software package at no extra cost. An intuitive graphical user interface makes the total functionality of the Extorr system available to the user. This starts with the first Pirani measurements, and continues on to ion gauge measurements and RGA partial pressure measurements. Complete pump down may be monitored both quickly and easily. The VacuumPlus program is fully interactive giving the user complete control of the graphical display. A number of graph or table windows may be opened, simultaneously, for monitoring multiple XT units. Data is captured and displayed in real-time. The user may choose to display data in torr, Pascal or amps. A logarithmic data display may be invoked so that partial pressures, which may vary by many orders of magnitude, may be displayed on a single graph. The software also allows for complete RGA probe control. There is easy mass scale tuning, sensitivity calibration, and ionizer setup. For further analysis, data files can be saved in a number of formats. Graphs may be set to a printer. Digital data may be saved in text format or an XML format for easy transfer into spreadsheets and other applications. Real-time streaming XML data is available for use in other user programs.

Exclusive Extorr Features

Extorr’s residual gas analyzers set a new standard for reliability.

• A solidly built vacuum probe with few troublesome screws.
• The filament and electron multiplier are protected by the Pirani gauge.
• Vacuum break, surprise outgassing, inadvertent vent, over pressure? No Problem!
• The electronic circuits are protected against probe shorts to the vacuum system walls.

Our RGA’s come with built-in Pirani and Ion gauges for complete vacuum measurement. You can do leak detection at any pressure. Extorr is the only RGA manufacturer that offers these features. RGA’s are great for qualitative partial pressure measurements, but can only be used for quantitative readings when periodically calibrated against an accurate ion gauge to adjust for sensitivity changes as the ionizer ages. This is because low energy ions (5-10 EV) are needed for separation in a quadrupole mass filter. An ion gauge uses much higher ion energies (150 EV) than the RGA ionizer and is much less susceptible to sensitivity decrease due to aging. The Extorr ionizer has two regions that produce both low and high energy ions simultaneously and two separate detectors. Other manufacturers will report total pressure readings using various schemes that use the low energy ions created in the ionizer. The problem is that the readings will also decrease as the ionizer ages. Other manufacturers tell you to calibrate using an ion gauge, but they do not give you the ion gauge.

• Small size without any compromises in performance.
• No fan is used due to efficient circuitry, an important consideration for clean rooms and general reliability.
• Probe is strong enough to stand on its own. It needs no support nipple and is able to penetrate deep into the vacuum chamber on a 2-3/4 inch UHV flange with no special hardware.

The computer interface uses a robust serial, optically isolated cable to connect the CCU to the host. Communications to the host computer are continuously checked for errors and retransmitted automatically without interruption of the data collection. The baud rate can be selected up to 115,200 for high speed on cables 50 feet or less. Lower the baud rate for even more noise immunity on longer cable runs.

If you want to upgrade or replace your electron multiplier, simply use a clean glove and snap it out with your fingers. No tools or disassembly of the probe are required. The CCU electronics will meter out just enough current to the electron multiplier to run it properly, avoiding destructive channel current during overpressure. We are so confident in the durability of the multiplier that we give a one year warranty against any failure, except of course, physical breakage or contamination.

If you do have a problem with your Extorr Residual Gas Analyzer, there is a software page that give complete diagnostic information about the probe and electronics. Over 90% of failures are able to be diagnosed and corrected over the phone or e-mail. By sending us the log from the Vacuum Plus software, we can tell exactly where the problem is and what to do about it.

We are confident that we have as good or better quality data as any instrument in this price range, giving you the best value. Designed for ease of use, easy to maintain, easy on your wallet.