ELTRA CS-2000, Manual

Page: 41 / 110

Analysis
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For even lower carbon samples, a furnace extension piece, supplied by ELTRA, needs to be
attached to the furnace inlet.
The reason is that the thick short combustion tube allows some air to enter the combustion
area. The air contains CO2 which is detected by the carbon cell. As the CO2 concentration
resp. the air flow entering the furnace is not necessarily constant, the varying CO2 of the air
leads to corresponding variations of the base line. For low carbon analysis, with sensitive CO2
cells, the entrance of the resistance furnace has to be restricted.
Using high carbon analysis in % range, resp. for high carbon IR-cells, the CO2 of the entering
air, practically doesn't have any influence on the results.
The combustion boats that are used are the slim quartz boats. They have to be used, not only
because the bigger ceramic boats cannot pass through the restricting attachment, but also
because the quartz boats have much lower blanks than the ceramic boats.
Even if the ceramic boats were able to pass through the attachment, they couldn't be used for
low carbon analysis anyway, because of their relatively high carbon blanks.
Installing the low carbon attachment:
Fig. 20: Installation of low carbon attachment
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