Zero Point Error; Oxymat 7 - Siemens SIPROCESS GA700 Operating Instructions Manual

Commissioning

9.5 Zero point error

Checking pressure switch for function
1. Increase the reference gas pressure until the pressure switch is triggered, meaning that the
switch contact opens.
2. Please ensure that the reference gas pressure is not more than 2 000 hPa above the sample
gas pressure.
The value when pressure is increasing (response pressure) is always higher than the value when
pressure is decreasing (release pressure). This so-called switching hysteresis of the pressure
switch is approx. 200 hPa.
9.5 Zero point error
Note
Zero point error because of surrounding gases
Keep the ambient air of the analyzer section free from the measured gas component; otherwise,
measurement results will be affected. Gases which exhibit cross-sensitivity to the measured gas
component must also not be present in the ambient air.
9.5.1

OXYMAT 7

Accompanying gases (interfering gases) cause a zero point deviation that is positive with
paramagnetic gases and negative with diamagnetic gases. The extent of this offset per 100 vol.
% accompanying gas, expressed in vol. % O
in the tables refer to nitrogen at 60 °C and 1 000 hPa absolute to IEC 1207/3.
Table 9-3
Accompanying gas (concentration 100 vol. %)
Ethane
Ethene (ethylene)
Ethine (acetylene)
1.2 butadiene
1.3 butadiene
n-butane
Isobutane
1-butene
Isobutene
Dichlorodifluoromethane (R12)
Ethanoic acid
n-heptane
n-hexane
Cyclo-hexane
94
Zero point error of organic gases
absolute, is listed in the following table. The values
2
Zero point deviation in
vol. % O
C H
2 6
C H
2 4
C H
2 2
C H
4 6
C H
4 6
C H
4 10
C H
4 10
C H
4 8
C H
4 8
CCl F
2 2
CH COOH
3
C H
7 16
C H
6 14
C H
6 12
Operating Instructions, A5E31874006-12
absolute
2
-0.49
-0.22
-0.29
-0.65
-0.49
-1.26
-1.30
-0.96
-1.06
-1.32
-0.64
-2.40
-2.02
-1.84
Rack-mounted device