In an effort to provide a more accurate gas measurement, CiSCO uses a calibration correction function to help offset minor error or drift in the CEMS gas analyzers. This function is performed automatically by the CEMS PLC .  It works by evaluating the results of the daily automatic calibration check procedure and developing correction parameters based on the results of the calibration check.  The analyzer response errors detected at both the zero response and the span response are used to create a linear representation of the analyzer’s response.   A correction formula is derived by subtracting this line from the line that represents a perfect calibration check (a 45-degree line where the analyzer would respond with exactly the same value as the calibration gas concentration) The PLC will then use this correction formula to adjust raw data form the analyzer  from that point until a new calibration check is performed. Calibration-corrected data is then passed to the data handling and reporting system.

It is important to note that this method is meant to adjust for small error or drift caused by the analyzers, and that only raw data during the calibration check is used to develop the correction parameters.  This way there is no possibility of covering up run away drift caused by stacking corrections over corrections.    Also, the correction formula is not applied if the analyzer fails Out of Control.

Cal correction is a standard feature of a CiSCO CEMS, however, this feature may be turned off by request of the user, or if local CEMS codes prohibit it.

Cal Correction acts similarly to a manual adjustment of the analyzer to the calibration gas standard.  Only, it is done automatically by the software which helps to minimize user intervention and maintenance on the CEMS analyzers.