Analytical Industries GPR-3100 Series Oxygen Purity Analyzer - Manual (Page 13)

Advanced Instruments Inc.
5 Operation
GPR-3100 Rev 2/05 6
Graph C illustrates these 'worse case' specifications that are typically used to develop an analyzer's
overall accuracy statement of +2% of full scale at constant temperature or +5% over the operating
temperature range. QC testing is typically <+0.5% prior to shipment.
Example: As illustrated by Graph A any error, play in the multi-turn span pot or the temperature
compensation circuit, during a span adjustment at 20.9% (air) of full scale range would be multiplied by
a factor of 4.78 (100/20.9) if used for measurements of 95-100% oxygen concentrations. Conversely, an
error during a span adjustment at 100% of full scale range is reduced proportionately for measurements
of lower oxygen concentrations.
Recommendation: The analyzer may be calibrated by using a certified span gas of 80-90% value of
the range of analysis. For example, for analysis on 90-100% range, use 98-99% oxygen as the span gas
and for analysis on 80-90% oxygen, use 96-98% oxygen as the span gas.
Note: The accuracy of the analyzer is given as the % of full-scale. Therefore, the calibration of the
analyzer must be done on the range of analysis or one range above the range of analysis. The analysis of
the sample gas must be carried out on the range that provides the required accuracy.