Servomex NanoTrace DF-760E, Instruction Manual

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126 DF-760E Service
Depending upon the nature of the application, Delta F suggests verifying the span
calibration of the analyzer approximately every 12 months using a gas with a known level
of oxygen. Span checks can be performed with gases in the range of 0 to 10 ppm.
However, reliable standard gas mixtures are readily available in the 4-7 ppm range.
The zero calibration is most important for applications requiring accuracy below 10 ppb.
For use in applications that are above 10 ppb, the zero calibration is not recommended for
newly installed instruments.
By far the zero calibration is the most important calibration for the NanoTrace Dual
Moisture/Oxygen Analyzer. From a stable zero calibration baseline, oxygen readings
below 1 ppb can be made accurately. In many measurement cases, the accuracy of the
oxygen reading are determined by the quality of the zero calibration. It is important to
check the zero periodically and make appropriate calibration adjustments.
From an initial start-up, the analyzer may take 7 to 14 days to reach a stable zero. After
achieving a stable zero baseline, the analyzer requires periodic zero checks and possibly
adjustments to ensure accuracy. For applications where the process is continuously
monitored, the zero check frequency guidelines in the table below should be used.
Oxygen Zero Check Frequency Guidelines
Typical Reading Maximum O
2
Impurity Zero Check Frequency
1.0 ppb and greater 10 ppb Once every month
0.2 to 1.0
ppb
5 ppb Twice per month
5 ppb Twice per month
0 to 0.2
ppb
1 ppb Once per week
1 ppb Once per week
Table 11: Zero Check Frequency
Experience with a particular application determines the optimum frequency of zero
checking.
Accurate oxygen readings can be made even though the zero is not completely stabilized,
such as after a start-up or after exposure to high oxygen concentrations. Simply calculate
the difference in concentration between the analyzer output on zero gas and the sample
gas. This comparison should be made over a short time span to avoid errors introduced by
a stabilizing zero.
NOTE
If the Active Zero Offset feature is in use, and the “Cal Zero”
message appears on the display, it is mandatory to do a zero
calibration.
9.3.2 Storage Conditions
If the analyzer is to be stored for extended periods of time, be sure that the temperature of
storage location does not exceed 50° C (122° F). Storage in direct sunlight can cause