► Observe the constants for converting the measuring signal and pressure.
► Convert the measuring signal into pressure:
p = 10
(U-c)
► Convert the pressure into the measuring signal:
U = c + log
10
p
6.2 Determining effective pressure with correction factors
The measuring signal is gas type-dependent. The characteristics apply for nitrogen (N
2
), oxygen (O
2
),
dry air and carbon monoxide (CO).
10
2
8
6
4
2
10
1
8
6
4
2
10
0
8
6
4
2
10
–1
8
6
4
2
10
–2
8
6
4
2
10
–3
10
–3
2
4
6
10
–2
2
4
6
10
–1
2
4
6
10
0
2
4
6
10
1
2
4
6
10
2
H
2
He
Ne
Xe
Kr
Ar
CO
2
Freon 12
Air
O
2
CO
N
2
p [hPa]
p
eff
[hPa]
Water vapor
Fig. 6:
Displayed pressure
Within the pressure range < 1 hPa, the display is linear.
Gas and vapor mixtures
Process gases are mostly mixtures of gas and vapor. Precise measuring of gas and vapor
mixtures is only possible using partial pressure measurement instruments, for example a
quadrupole mass spectrometer.
Gas type
Calibration factor (C)
Air, oxygen (O
2
), carbon monoxide (CO), nitrogen (N
2
)
1.0
Hydrogen (H
2
)
0.5
Carbon dioxide (CO
2
)
0.9
Water vapor
0.5
Helium (He)
0.8
The correction factors provided are mean values.
Operation
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