Delta F Oxygen Cell Background Gas Correction Factors; Correcting For Different Background Gases - GE Moisture Image 1 Series Service Manual

Delta F Oxygen Cell
Background Gas
Correction Factors
Correcting for Different
Background Gases
Troubleshooting and Maintenance
The factory calibration procedure for Delta F oxygen cells uses
nitrogen as the reference background gas. The Series 1 will measure
oxygen incorrectly if the transport rate of oxygen through the cell
diffusion barrier is different than the cell is calibrated for. Therefore,
if you want to use a background gas other than nitrogen, you must
recalibrate the meter for the desired gas.
The Series 1 can easily be recalibrated for a number of different
background gases. Correct your system for the appropriate
background gas by referring to Table 2-7 and entering the correct
current multiplier into the "Oxygen Probe Calibration" section of the
System Calibration Menu. A detailed explanation and description of
this process follows.
Note: In order for you 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 the factory for
the nitrogen calibration sheet.
A single "Background Gas Correction Factor" based on the reference
nitrogen measurement can be derived for each background gas
because, in practice, the diffusion rate for a typical background gas is
stable and predictable and because the cell's response is linear. The
current multiplier that is entered into the "Oxygen Probe Calibration"
section is the inverse of this "Background Gas Correction Factor."
For example, Table 2-7 below represents the calibration values (two
points) for a specific oxygen cell calibrated in nitrogen. This data is
supplied with the cell and is stored in the user program.
Table 2-7: Oxygen Cell Calibration Data on Calibration
Sheet (referenced to nitrogen)
Zero Calibration Point
Span Calibration Point
Zero PPM Value = .0500 PPM
V
Zero µA Value = .9867 µA
Span PPM Value =100.0 PPM
V
Span µA Value = 300.1 µA
June 2003
V
V
2-25