Granville-Phillips Micro-Ion 354 E Series, Instruction Manual, Page: 48 / 54

Appendix B
48
Micro-Ion E Module Instruction Manual 354011, Rev. A
The amount of ion current for a given emission current and pressure
depends on the Micro-Ion E gauge design. This gives rise to the definition
of ionization gauge sensitivity, frequently denoted by “S”:
Micro Ion gauge sensitivity for N
2
or air is 20/Torr (0.15/Pa, 15/mbar).
The module electronics for the gauge varies the heating current to the
filament to maintain a constant electron emission and measures the ion
current to the ion collectors. The pressure is then calculated from these
data.
S
Ion current
Emission current Pressure
×
---------------------------------------------------------------------- =