Compare Description Drawings, CAD & Specs Availability Price
835 vacuum quality monitor controller
Controller, Vacuum Quality Monitor, 1 - 145 amu, 110 VAC
835 vacuum quality monitor controller
Controller, Vacuum Quality Monitor, 1 - 300 amu, 110 VAC
835 vacuum quality monitor gauge
Vacuum Quality Monitor Gauge, 1 - 145 amu, Demountable Envelope
835 vacuum quality monitor gauge
Vacuum Quality Monitor Gauge, 1 - 300 amu, Demountable Envelope
390 micro-ion atm vacuum transducer
Vacuum Transducer, for 835 VQM, 1x10-9 Torr to ATM
Software Suite, Vacuum Quality Monitor


  • Mass Range
    1-145 amu in 85 ms
    1-300 amu in 120 ms
  • Data I/O
    USB 2.0, full speed, 12 Mb/sec
  • Trigger In (BNC)
    50 ohm, positive TTL edge trigger, 1 ms minimum
  • Trigger Out (BNC)
    50 ohm, active high, TTL, frame scan, or VQI status
  • Analog In (BNC)
    10K ohm, 0-10 V, 12 bit resolution
  • Analog Out (BNC)
    0 to +5 V with 30 KHz 3 db bandwidth, raw data scan output
  • Front Panel LEDs
    ExT TP, USB, Trigger IN, Trigger OUT, Analog IN, Analog OUT
  • Operating Temperature
    0° to 40°C (32°F to 104°F)
  • Storage Temperature
    0° to 80°C (32° to 176°F)
  • Relative Humidity
    <90%, non-condensing
  • Dimensions
    178.5 x 104.9 x 40.1 mm (7.03 x 4.13 x 1.58 inches)
  • Weight
    720 grams (25 ounces)
  • Compliance
  • Gas Display Table
    Automatic listing by amu or gas type (user selectable)
  • Input Power Plug
    DC power jack, 5.5 mm OD x 2.5 mm ID x 11 mm long


VQM® Vacuum Quality Monitor System UHV Performance

Demonstration of the performance characteristics of the MKS Instruments, Granville-Phillips® Vacuum Quality Monitor System (VQM®).

System Description

In any vacuum system, it is critical to know the vacuum pressure. In many cases, it can be just as important to know the composition of the gases in the system. The 835 VQM is a mass spectrometer that operates from UHV to 1 x 10-5 Torr and accurately measures the gases in the vacuum chamber. The VQM system consists of an autoresonant ion trap mass spectrometer gauge, a VQM Controller and VQM Viewer software that converts raw data to actionable information. The system is ratiometric, meaning that it determines the ratio of each gas to other gases in a vacuum chamber. It is usually coupled with a total pressure gauge to provide partial pressures of each gas which provides an indication of the quality of the vacuum in a chamber.

Out-of-the-box you see your 10 most prevalent gases, total pressure trending (with optional total pressure gauge), partial pressure trending, spectral display, data logging, data capture, gas fitting library for 10 gases, and leak check. The Controller and Gauge only requires a maximum of 15 watts to operate and offers the flexibility to remotely mount the 835 VQM Gauge using a cable from 1 to 50 meters long.

Vacuum Quality Monitor Theory of Operation

Autoresonant ion trap mass spectrometer technology represents an entirely new way of mass selectively ejecting ions from an electrostatic ion trap. The 835 VQM mass spectrometer gauge is natively a ratiometric measurement device that provides detailed compositional analysis of a gas mixture. The ionizer is a filament assembly that generates ions directly inside the ion trap through electron impact ionization. An electrostatic field traps the ions, and they oscillate at their natural frequency within the ion trap. The frequency of oscillation is inversely proportional to the square root of their mass-to-charge ratio. The ions are ejected through an autoresonant energy pumping process using a low amplitude RF scan. An electron multiplier collects the ejected ions and produces a current proportional to the ion concentration.

Field Replaceable Assemblies

The filament and electron multiplier are easily replaced by your own service technicians. Replacement kits provide everything needed – including an easy-to-follow instruction guide – to assure quick, simple, and cost effective replacement, as well as maximizing system uptime.

Field Replaceable Filament

Common Applications

The 835 VQM is typically used for any manufacturing or experimentation process that occurs in a vacuum (glass coating, semiconductor manufacturing, beam line gas analysis, etc.). Primary usage includes system baselining, post chamber PM verification, leak detection, contamination monitoring, process monitoring, and checking the quality of the vacuum in the system.

System Features

  • Compact Size and Remote Mounting: The small size of the VQM gauge allows the system to be used in applications where space and weight limitations are crucial. The gauge is not mounted to the controller, thereby making the system ideal for use in harsh environments such as accelerators and beam lines where radiation is known to cause some electronics to malfunction. In addition, multiple gauges can be operated by just one VQM Controller by simply moving the interconnect cable to a different VQM gauge, thereby eliminating the requirement of multiple controllers on a process chamber or system.
  • UHV Compatibility: The materials, composition and construction of the 835 VQM Gauge are commensurate with standard ultra-high vacuum technology and UHV gauging including stainless steel, ceramics, and refractory materials.
  • High Resolution Low Mass Spectra: Unlike current quadrupole mass spectrometers, the VQM System accurately reports the spectra of low amu gases, such as helium and hydrogen, and includes hydrogen 1 in the spectra.
  • Super Fast Vacuum Quality Measurement: The VQM System provides full data collection, spectral deconvolution, and data logging at 85 msec capture rates over the full 1–145 amu range. Optionally, an entire 1-300 amu scan can be performed in 120 msec.
  • Ultra Low Power Requirement: The VQM Controller and Gauge system requires only 15 watts (maximum) to operate without the optional total pressure gauge. Using a low-power electrostatic field together with a small RF signal for ion ejection delivers a system that requires very low power.
  • Intuitive Operation: The easy-to-use 835 VQM Viewer application provides a full set of features and functions to enable quick vacuum quality measurement and data logging, flexible data presentation and viewing options, leak detection mode, and system configuration options.
  • Out-of-the-Box Functionality: The VQM System provides unparalleled ease of use with a clear listing of the 10 most prevalent (or user selected) gases with ratio (normalized), percent (%), and absolute amplitudes that are listed by amu or from a library of Reference Gases. You also get total pressure and partial pressure trend graphs, and full spectral data. A few mouse clicks gives you a log of the histogram data that is readable in the Viewer software or using Microsoft® Excel® or other common data analysis programs.
  • Hassle-Free Installation: The VQM mass spectrometer gauge is remotely mounted using interconnect cables up to 50 meters long. The VQM Controller can be used as a bench-top, rack-mount, or custom-mount solution.
  • Simple Calibration: Calibration can be completed in seconds with just a few clicks of the mouse using any single gas, including any gas that is already in your vacuum system.

VQM Viewer Software Application Features

The 835 VQM Viewer Software Application provides the fastest and easiest way to access the full functionality and optimize the performance of the instrument. The Viewer Application is Windows-based and communicates with the VQM Controller through a USB 2.0 COM port.

Vacuum and system technicians will immediately benefit from the data-mining functions built into the application, including mass peak finding and gas identification. There is no need for an advanced mass spectrometry expert to determine what gases are in your system. Simple, easyto-understand screens instantly display which gases, percentages, ratios, and pressures are present.

Advanced users will find that the full set of adjustments (advanced settings) and data available in the tune screens provide a very convenient way to characterize and optimize the performance of the system.

  • Easy Navigation: When the VQM System is connected to a Host/PC with the VQM Viewer Application, the displays on the computer monitor enable the user to select and view many functions and readouts. A row of icons across the top of the screen provide quick links to all of the operation and tuning functions. The first group of icons (on the left side of the screen) are the primary functions used for connecting and powering the gauge and starting the spectral scan. The second group of icons control the data display, modes of operation, and system settings (preferences). The third group of icons are for logging and save functions. Context sensitive help is available to provide system operation guidance.
  • Leak Checking: The leak checking screen allows you to select from a list of leak-check gases (Hydrogen, Helium, Nitrogen, Argon, and Freon) and displays a graph showing the current leak limit and a trend graph of the partial pressure of the selected gas. An audible tone can also be used to track the leak gas.
  • Easy to Calibrate: The VQM System is very easy to calibrate using any gas (1–145 amu) already in the vacuum chamber. Simply select any known peak and click on the arrows to align the known peak to the proper amu setting. All other gases will also display correctly. A zoom function makes it easy to see the waveform of the selected peak.
  • Data Logging: Raw data or processed data can be logged at full scan rates for a user selected length of time. The processed data is much smaller as it only saves the amplitude at each amu. Processed data logging allows you to select the logging interval to save disk space when recording for long periods of time. Logs can be displayed in the viewer software and raw logs can be played back to allow for further analysis of the data. There is also a save function that saves a snapshot of the raw, averaged data, plus the histogram and trend information for all species. Data is saved in a csv (comma-separated values) ASCII files.

Summary Screen

The Viewer software collects, analyses, and interprets mass spectra. The software averages the mass spectra, finds and quantifies the peaks, and displays that information on the computer monitor. Live displays of scan data show the gases in the vacuum chamber (up to 10 gases/masses), pressures, trends, total pressure, averaging, and the spectrum histogram.

Tuning Functions

The Tune Screen is used for calibration, electron multiplier gain adjustment, RF amplitude adjustment, and ion trap configuration. The tune screen provides access to the raw spectral output of the mass spectrometer and also to the header information which provides specific information on parameters, status, and hardware. The tune screen also provides access to the factory default and user settings. Advanced mass spectrometry experts can use the tune screen capabilities to customize the instrument for specific operating parameters. An Auto Tune function automatically determines the appropriate settings for optimum system performance.

Displayed Results

Gas analysis results are displayed as ratios (normalized), percentages (%), and absolute values (with the optional total pressure gauge). Graphical screen displays show the total pressure, partial pressure, and full spectral data. Partial pressure trend graphs and a leak testing screen allow monitoring specific gas concentrations and partial pressures as a function of time.


The Histogram displays the spectrum in a histogram format and can display either normalized values or partial pressure (if a total pressure gauge is connected).

VQI (Vacuum Quality Index)

Audible alarms and a digital output can be driven by custom equations which monitor the total pressure, partial pressures or preferences. The equations can use Boolean AND and OR functions together with less than, greater than, and equals operators. For the “equals” operation, a tolerance can be provided. The VQI equation can be manually entered or automatically created from a stored spectrum.


The Trend graph on the summary screen shows a 15 minute view of the top 10 gases in the system. The display can use either log or linear scale. A zoom function allows better visibility. There is also an infinite time period trend graph. To fit a longer time scale on the graph and keep the data storage size reasonable, the trend screen will drop intermediate data points as needed.

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