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Ionization Gauge Tubes, Bayard-Alpert Type

Catalog F26-F27
Ion Gauge Tubes, Bayard-Alpert Type
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Series G Ionization Gauge Tubes are hot cathode gauges of the Bayard-Albert Type intended for pressure (density) measurement from 10-3 Torr down to 3 x 10-10 Torr. These tubes have been designed to provide long trouble-free operation and are carefully cleaned, assembled and packaged so that they will not contaminate your clean system. Both the burn-out-resistant iridium type and the dual tungsten types are interchangeable.

G Series

Burn-Out Resistant Iridium Filament (G Series)

The burn-out-resistant filament is made of iridium with a layer of thoria cataphoretically coated on it. This provides long filament life and stable, easily controlled electron emission at relatively low filament operating temperatures. Because iridium does not oxidize rapidly, even at high temperature, occasional accidental exposure to atmospheric pressure while hot will not appreciably damage or shorten the active life of the filament. The burn-out resistant model is designed for convenient and reliable connection to standard connectors.

T Series

Dual Tungsten Filament (T Series)

The dual tungsten filament model is also designed for use with the same gauge cables. By connecting control unit filament leads to contacts "C" or "D" of the connector, either filament may be used by merely reversing the connector 180 degrees on the tube base. Because the two filaments are independently connected, one may be used to operate the gauge and the other operated as a desorption filament.

The bifilar design supports the grid at its midpoint so that the unsupported length of grid wire is only half that in conventionally wound grids. Thus the tendency to sag during outgassing is greatly reduced.

Bayard-Alpert Ion Gauge can measure vacuum from 10-10 to 10-3 torr.


  • Bayard-Alpert Design
  • Dual Tungsten or Burn-out Resistant Iridium
  • Non-sag Bifilar Grid
  • Linear Response
  • 3/4" or 1" Pyrex or Kovar Tubulation
  • Response from 10-10 to 10-3 torr


Physical Data
Filament Voltage 3 to 5 Volts AC
Filament Current 4 to 6 Amps AC
Grid Voltage +150 Volts
Grid Outgas 6.3 to 7.5 Volts@ approx. 10 Amps.
Collector Voltage -20 to -50 Volts
Sensitivity Tungsten Filament: 100μa/μ @8 ma grid current (Nitrogen)
Iridium Coated Filament: 100μa/μ @10 ma grid current(Nitrogen)
Linearity 10-4 to 10-10 Torr @ 10 Ma
10-3 to 10-4 Torr @ 1 Ma grid current
Electrical Data
Bulb Material Nonex 7720 Glass
Tube Diameter 2 1/4" max. O.D.
Tube Length 6 3/4" Maximum
Tabulation See Chart
Mounting Position For best results, it is recommended that tube be mounted vertically
Recommended Either Winchester Electronics
Socket Connector P/N A7SH or Continental Connector P/N 7-16SH


Connector Plug Data

The G Series is designed for convenient and reliable connection to a standard connector. The burn-out-resistant version is mechanically and electrically interchangeable with similar models using Continental Connector Corp. type 7-16S connector. (Refer to above diagram).

Gauge Tube Pin Data


The two tungsten filament version is designed for use with the same connector. Connect control unit grid leads to contacts "A" and "H" and filament leads to contacts "C" and "D" of the connector. Filaments can then be switched by merely reversing the connector 180 degrees. This eliminates the possibility of damage to tube by applying grid outgassing currents to filament (s). (Refer to above diagram).

Cross Reference

Cross Reference Table

Ion Gauge Tube
Part No. Description Price
G75P 3/4 in Pyrex Iridium $179.254 or more: 3% off.
G75K 3/4 in Kovar Iridium (Finnigan #00105-01500), Bayard Alpert $180.384 or more: 3% off.
T85P 3/4 in Pyrex Tungsten $115.004 or more: 3% off.
T85K 3/4 in Kovar Tungsten $127.004 or more: 3% off.
G100P 1 in Pyrex Iridium $160.314 or more: 3% off.
G100K 1 in Kovar Iridium $191.254 or more: 3% off.
T110P 1 in Pyrex Tungsten $178.004 or more: 3% off.
T110K 1 in Kovar Tungsten $108.004 or more: 3% off.
G75KHS 3/4 in Kovar Iridium/Thoria, Hi Sensitivity, 1.6 (Finnigan #00105-01510) $210.004 or more: 3% off.
G100KF25 NW25 Flange Iridium for HP5989 $195.00
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