What is purge air (or cleaning air) and why are not all probes equipped with this feature?

What is purge air (or cleaning air) and why are not all probes equipped with this feature?

Purge air is used on our %C probes (CarboProbe ZI Pro, ZS Pro, ST and ST-E) only to clean the ZrO2 measuring element with a fresh air flow. 

In heat treatment, the measuring element can become clogged with carbon soot deposits (due to the carbon-rich atmosphere in which these probes are used). A supply of fresh air “burns off” the soot and frees the measuring element from this deposit. If this cleaning is not carried out at regular intervals, the probe measurement will be distorted.

Important:  The burning of soot leads to a significant increase in temperature which can destroy the measuring element if left uncontrolled (see the probe’s operating instructions for more information).

Purge (or cleaning) air is not available for the CP, DS, LT and HT CarboProbes. These cannot be used in carburising atmospheres (with carbon). This means that there are no soot deposits that can be burnt off by the cleaning process. Cleaning air cannot clean deposits other than carbon deposits (e.g. incineration residues).

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