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Model GFC7000E Instruction Manual Calibration Procedures
04584 Rev A1 129
7. CALIBRATION PROCEDURES
This section contains a variety of information regarding the various methods for calibrating a
Model GFC7000E CO
2
Analyzer as well as other supporting information.
NOTE
The procedures in this section assume that the calibration password feature is disabled
(the instruments default state). If it is enabled a password prompt screen (see Section
6.3.1) will appear after the CAL, CALZ or CALS buttons are pushed but before the
instrument enters the associated calibration mode.
7.1. Before Calibration
The calibration procedures in this section assume that the Range Type, Range Span and units of
measure have already been selected for the analyzer. If this has not been done, please do so
before continuing (see Section 6.7 for instructions).
All Gas lines should be PTFE (Teflon), FEP, glass, stainless steel or brass.
NOTE
If any problems occur while performing the following calibration procedures, refer to
Chapter 11 of this manual for troubleshooting tips.
7.1.1. Zero Air and Span Gas
To perform the following calibration you must have sources for zero air and span gas available.
Zero Air
is similar in chemical composition to the Earth’s atmosphere but scrubbed of all
components that might affect the analyzer’s readings. Zero air should contain less than 25 ppb of
CO
2
and other major interfering gases such as CO and Water Vapor. It should have a dew point
of -5°C or less
Span Gas
is a gas specifically mixed to match the chemical composition of the type of gas being
measured at near full scale of the desired measurement range. It is recommended that the span
gas used have a concentration equal to 80% of the full measurement range.
If Span Gas is sourced directly from a calibrated, pressurized tank, the gas mixture should be CO
2
mixed with Zero Air or N
2
at the required ratio.
Zero air generators that condition ambient air by drying and removal of pollutants are available on
the commercial market such as the Teledyne Instruments Model 701 Zero Air Generator. We
recommend this type of device, in conjunction with a CO
2
scrubber such as soda-lime, for
generating zero air.