Installation and connection
3.3 Gas preparation
FIDAMAT 6-G
3-6
Operating instructions, 07/2006, A5E00478463
3.2.3
Gas and electric connections
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Figure 3-1
Gas and electric connections of the FIDAMAT 6 G
3.3
Gas preparation
Requirements to purity of operating and test gases
The Fidamat 6-G is often used to measure hydrocarbons with a concentration of less than
1 ppm. For such measurements, it is important that the operating gases used (hydrogen,
combustion air and zero gas) are very pure. The higher the purity of the operating gases, the
lower the zero current and thus the noise that determines the lower detection limit. If, for
example, the measured value of the sample gas is less than the measured value of the zero
gas, the zero gas is contaminated or the contamination comes from the gas supply lines and
other parts outside the Fidamat 6-G.
If plastic tubes (including PTFE) are used, the diffusion of hydrocarbons through the walls
must also be considered. Therefore, when measuring low concentrations, the supply lines for
the supply gases must be made of high-purity steel or copper pipes. Depending on the
application, the purity level of the operating gases must also be raised from 5.0 to 6.0.
For operation, it is also sufficient to connect final cleaning facilities directly to the gas input
points on the Fidamat 6-G by means of purified metal connectors. Cleaning facilities of this
type can include filters (activated carbon) or catalytic converters that break down
hydrocarbons. The use of final cleaning facilities is more economical in the long run than the
use of operating gases with a purity level of 6.0. High-purity pipes and suitable final cleaning
facilities can be obtained from suppliers of accessories for gas chromatography.