4.2.1.1 CALIBRATION – introduction
For best application-driven accuracy, the Model 7100 is capable of a flexible two-point calibration,
customized by the user to fit the application. There is no need for a fixed “zero” calibration, and
calibration gases may be selected almost anywhere within the analyzer’s configured range.
The user may select “high” and “low” calibration gases that profile the in-service oxygen measurement
range. When gases are selected properly, the analyzer recognizes them as high and low calibration
gases automatically during the calibration sequence and applies any user-entered correction factors.
To calibrate the system (section 3.2.1.3), the user just applies a gas to the sensor, adjusts the reading on
the analyzer control panel to match the oxygen concentration in the gas, and repeats the same simple
procedure using another gas. The analyzer does the rest. When the procedure is complete, the analyzer
is aligned to the user’s specific measurement needs.
4.2.1.2 CALIBRATION Step-1: Select calibration gases
To calibrate the Model 7100, the user will select two gases with oxygen concentrations that profile the
expected average upper and lower extremes of the in-service oxygen measurement range. This manual
will refer to those gases as the “high” and “low” calibration gases respectively (Figure 19).
To set up automatic recognition of selected calibration gases, a few guidelines must be followed. The
Model 7100 uses a field-adjustable reference range setting called Assume Low End Calibration in the
analyzer setup menu (sections 4.1.1.6 and 4.1.2.16) to determine which gas is the LOW calibration gas,
and which one is the HIGH calibration gas.
Proper system operation requires that the user select one gas within the Assume Low End Calibration
range and another gas that is above that range. During the calibration procedure, the Model 7100 will
assume the former is the intended LOW calibration gas, and the latter is the intended HIGH calibration
gas.
The following calibration gas sources can be used to calibrate the Model 7100:
• Certified Standard grade bottled calibration gas – 10 PPM to 1,000 PPM O
2
4.2.1.2.1 Selecting LOW calibration gas
The LOW calibration gas must have an oxygen concentration > 10 PPM, and within the limits of the
Assume Low End Calibration range in the analyzer setup menu. Refer to Appendix C for the
factory-configured Assume Low End Calibration range setting.
The Assume Low-End Calibration range is user-adjustable to provide best on-line measurement
range profiling. Appendix E shows all settings available in the user setup menu, and an indication
of those settings applicable to the Model 7100. To change the Assume Low-End Calibration range
setting, refer to sections 4.1.1.6 for control panel access, or 4.1.2.16 for computer access to the
user-setup menu.
4.2.1.2.2 Selecting HIGH calibration gas
The HIGH calibration gas may have an oxygen concentration anywhere above the upper limit of the
Assume Low End Calibration range, and within the configured range of the Model 7100 analyzer.
For best accuracy, select a high calibration gas between ~80 % and ~120 % of the expected
highest in-service reading, and within the allowable calibration gas limits (10 PPM – 1,000 PPM).
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