Analytical Industries GPR-1000 ATEX Portable Trace PPM Oxygen Analyzer - Manual (Page 18)

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Both the Zero Calibrate and Span Calibrate functions result in the following displays:
PASSED
CALIBRATION
OR
FAILED
CALIBRATION
Satisfying users that the zero offset is reasonably acceptable for their application can be accomplished much
quicker. Unless the zero gas is contaminated or there is a significant leak in the sample connections, the analyzer
should read less than 100 ppm oxygen within 5 minutes after being placed on zero gas.
The maximum zero calibration adjustment permitted is 60% of the lowest full scale range available, which normally
is 1 ppm. Thus the maximum zero calibration adjustment or zero offset is 6 ppm oxygen. Accordingly, the
analyzer’s ZERO has not been adjusted prior to shipment because the factory conditions are different from the
application condition at the user’s installation.
Factory Default Zero:
Refer to Appendix A, the software will eliminate any previous span calibration adjustment and display the actual
the signal output of the sensor at a specified oxygen concentration. For example, assuming a zero gas is
introduced, the display will reflect an oxygen reading representing basically the zero calibration adjustment as
described above. This feature allows the user to test the sensor’s signal output without removing it from the sensor
housing.
Span Calibration
Maximum drift from calibration temperature is approximately 0.11% of reading per °C. Analyzer is calibrated at the
factory. However, in order to obtain reliable data, the analyzer must be calibrated at the initial start-up and
periodically thereafter. The maximum calibration interval recommended is approximately 3 months, or as
determined by the user’s application.
Calibration involves adjusting the analyzer electronics to the sensor’s signal output at a given oxygen standard, e.g.
a certified span gas with an oxygen content (balance nitrogen) approximating 80% of the next higher full scale
range above the intended measuring range is recommended for optimum accuracy, see Calibration and Accuracy.
Calibration with ambient or instrument air (20.9% or 209,000 ppm) is recommended when installing a new sensor
or when a certified gas is not available.
Factory Default Span
The software will set the SPAN adjustment based on the average oxygen reading (actually the sensor’s signal
output) at a specified oxygen concentration. For example, when a span gas is introduced, the micro-processor will
display an oxygen reading within +50% of the span gas value. This feature allows the user to test the sensor’s
signal output without removing it from the sensor housing.