Delta F Oxygen Cell Background Gas Correction Factors; Correcting For Different Background Gases - GE moisture.iq User Manual

7.4 Delta F Oxygen Cell Background Gas Correction Factors

The factory calibration procedure for Delta F Oxygen Cell uses nitrogen as the reference background gas. The
moisture.IQ will measure oxygen incorrectly if the transport rate of oxygen through the cell diffusion barrier is
based on a different background gas. Therefore, if you want to use a background gas other than nitrogen, you
must recalibrate the meter for the chosen background gas.
Note: To use the current multipliers in this chapter, your Calibration Data Sheet should contain calibration data
for nitrogen. If your calibration data sheet contains data for a background gas other than nitrogen,
contact BHGE for the nitrogen calibration sheet.

7.4.1 Correcting for Different Background Gases

A single Background Gas Correction Factor based on a reference nitrogen measurement can be derived for each
background gas because the diffusion rate for a typical background gas is stable and predictable and because
the oxygen cell response is linear.
For example, Table 9 below lists the calibration values at two points for a specific oxygen cell calibrated with
nitrogen as the background gas. Such data is supplied with the oxygen cell and is stored in the user program.
If this oxygen cell is used in a background gas other than nitrogen, you must enter the gas's correction factor, as
listed in Table 10 on page 92. Then, the moisture.IQ will apply the appropriate correction to the measured
oxygen signal. Although the original calibration values for nitrogen are programmed into the moisture.IQ,
the meter uses the correction factor to determine the actual oxygen concentration.
moisture.IQ User's Manual
Table 9: Oxygen Cell Calibration Data (ref. to nitrogen)
Zero Point Calibration
Span Point Calibration
Zero PPM Value = .0500 PPM
V
Zero μA Value = .9867 μA
Span PPM Value =100.0 PPM
V
Span μA Value = 300.1 μA
Chapter 7. Maintenance
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