Appendix
GA09313_0202 – (2008-02) –
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Oerlikon Leybold Vacuum
29
Indication range below 10
-5
mbar
In the range below 10
-5
mbar, the pressure indication is linear. For gases other than
air, the pressure can be determined by means of a simple conversion formula:
p
eff
= C × pressure reading
where
Gas
type
C
Air
(O
2
, CO, N
2
) 1.0
Xe
0.4
Kr
0.5
Ar
0.8
H
2
2.4
Ne
4.1
He
5.9
These conversion factors are average values.
A mixture of gases and vapors is often involved. In this case,
accurate determination is only possible with a partial pressure
measurement instrument, e.g. a quadrupole mass spectrometer.
