IGM402 Hornet™ Hot Cathode



IGM402 Hornet is the first modular miniature hot cathode Bayard-Alpert ionization vacuum gauge capable of operating 1 ionization and up to 2 convection gauge sensors simultaneously. The pressure measurement range of the IGM402 is 1.00E-09 to 1,000 Torr.

The IGM402 can combine the vacuum measurements from the ionization gauge and one of the convection gauges to provide full range vacuum measurements from high vacuum to atmosphere, or simply operate the ionization gauge and the 2 convection gauges as individual gauges.

IGM402 is available with various fittings including NW16KF, NW25KF, NW40KF, 1 1/3 in. Mini-Conflat, 2 3/4 in. Conflat, 3/4 in. O.D. Tube (O-ring compression) and 1/2 in. Cajon 8VCR female.


  • Full measurement range of 1.00E-09 Torr to 1,000 Torr
  • Built-in controller with bright 3-channel OLED digital display
  • User programmable display units in Torr, mbar or Pa
  • Operates 1 ionization and up to 2 convection vacuum gauges
  • Significant cost savings in controller, foot-print, cabling and sensor replacement
  • 3 analog outputs and 3 setpoint relays
  • RS485 serial communications
  • CE and RoHS compliant
  • Standard warranty of 18 months


What is the principle of operation?

The hot cathode Bayard-Alpert ionization vacuum gauge operates by ionizing the gas inside the gauge and then measuring the number of ions generated. The ions are then collected giving a measurement of the density or pressure of the gas inside the transducer. The various electrodes used in the transducer design are a collector surrounded by a circular grid with one or two filaments outside the grid.

An electric current is passed through the filament to cause the filament temperature to increase. As the filament temperature is increased, electrons are emitted from the filament surface. The bias voltage between the filament and the grid will accelerate the electrons toward the grid. Most electrons will pass through the grid volume and exit the other side of the grid and then be drawn back into the grid for another traversal through the grid volume. Eventually, most electrons will impact the grid surface generating a current between the filament and the grid which is referred to as the emission current. The electronic controller is designed to maintain a constant, selectable emission current which is independent of pressure. While an electron is traversing inside the grid volume, it may collide with a gas molecule and ionize it which removes an electron. The ionized gas molecule, which now has a positive charge because it is missing an electron, will be attracted to the collector which is at ground potential. A current will be generated by the flow of ions to the collector which is known as the ion or collector current. An electrometer will measure the small ion current generated and a pressure, which is proportional to the ion current, can be calculated.

What is the measurement range of the IGM402?

  • 1.00E-09 to 1,000 Torr
  • 1.30E-09 to 1,333 mbar
  • 1.30E-07 Pa to 133 kPa

Why is the IGM402 referred to as a “Module”?

A module is a complete vacuum gauge which combines the sensor and electronics (controller) in one assembly requiring no external controller to operate. The IGM402 is a vacuum gauge module with a built-in controller, display and it also provides process control signals.

What is the ion gauge with dual convection mean?

The IGM402 is the first modular ionization vacuum gauge capable of operating two convection gauges simultaneously. The IGM402 Hornet can combine the vacuum measurement from the ion gauge and a convection gauge to provide wide range measurements from 1.00E-09 to 1,000 Torr, or simply operate the ion gauge and the two convection gauges as individual gauges.

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Trademark Acknowledgements listed in the IGM402 Data sheet.