Compare Model Drawings, CAD & Specs Availability Price
835 vacuum quality monitor differential pump system
Differential Pumping System, Orifice 3, 90 - 3000 mTorr, Manual, 1 - 145 amu
Differential Pumping System, Orifice 2, 9 - 350 mTorr, Pneumatic, 1 - 145 amu
835 vacuum quality monitor differential pump system
Differential Pumping System, Orifice 3, 1 - 45 mTorr, Manual, 1 - 145 amu
835 vacuum quality monitor differential pump system
Differential Pumping System, Orifice 3, 1 - 45 mTorr, Manual, 1 - 300 amu


  • Mass Range
    1 to 145 amu or 1 to 300 amu
  • Operating Temperature
    5°C to 40°C (41°F to 104°F)
  • Weight
    10.88 Kg (24 pounds) plus the weight of the gate valve
  • Pressure Range
    3 Torr to 10-5 Torr through orifice, to 5x10-9 Torr through bypass gate valve
  • Resolution
    120 Full Width Half Maximum (FWHM), 180 resolution for the 300 amu system
  • Response Time
    85 ms (1–145 amu) or 120 ms (1-300 amu)
  • Dynamic Range
    2 decades for single scan, 3 or more with averaging
  • Exposed Materials
    304L Stainless Steel, 316L Stainless Steel, Alumina Ceramic, Al2O3 98% Min., Nickel, Molybdenum, Ag/Cu eutectic braze, Gold, Iridium, Yttria, Y2O3 99.95%, Lead Glass (multiplier body), Chromium, Viton, Copper


Differential Pumping Operation

Standard VQM Differential Pump System Setup

A pressure differential between the vacuum chamber and the VQM gauge is achieved by limiting the conductance to the sensor using an orifice in the gate valve and pumping the sensor with a turbo pump. The orifice size is specified based on the pressure in the vacuum chamber. The bypass gate valve can be opened during base out if the chamber is below 10-5 Torr. If base out is above 1x10-5 Torr, the bypass valve is not needed. The bypass valve can be controlled manually or electronically. An optional isolation valve can be used to isolate the entire differentially pumped system from your vacuum chamber when venting the chamber or when gas analysis is not needed.

The 835 DPS complete system includes the following components:

  • 835 VQM Partial Pressure Gauge
  • 390802 Micro-Ion Total Pressure Gauge
  • Bypass Gate Valve with Orifice
  • Turbo Pump
  • Roughing Pump with Hose
  • Interconnect Cables
  • VQM Controller
  • VQM Viewer Software

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.

VQM® Viewer Software Highlights

  • Intuitive graphical user interface
  • Displays the top 10 gases in the vacuum chamber
  • Single gas calibration
  • Mass spectrum output
  • Pressure vs. time trend display
  • Leak detection with graphic display
  • DSP for noise reduction and peak finding
  • Logging of data
  • Advanced settings and tuning functions
  • Built-in contextual help files

Pressure Ranges

Operating pressure range is determined by the orifice size selected.

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