GE XMO2, User Manual

Page: 44 / 196

September 2007
4-2 Field Calibration
Enhancing the Factory
Calibration
When your XMO2 transmitter was calibrated at the factory, the actual
factory calibration data points were entered into the XMO2 software.
If requested on the original order, calibration data points for expected
field background gas composition and/or measurement cell pressure
variations may also have been entered. To supplement this factory
calibration data, calibration data points generated in the field for these
parameters can be added into the XMO2 software. Refer to Chapter 6,
General Programming , for complete instructions.
The factory calibration can be further enhanced by performing
periodic recalibrations in the field. The XMO2 then uses the new
calibration data to create
offset and drift curves that compensate the
original factory calibration data for variations that occur in the field.
Refer to Chapter 5,
Basic Programming , for details on viewing the
current Offset Curve (one-gas calibration) and/or Drift Curve (two-
gas calibration) being used by your XMO2.
When making a measurement, the XMO2 uses the Offset Curve or
Drift Curve , along with any background gas and/or cell pressure
compensation data, entered at the factory or in the field, to update the
factory calibration data.
To maintain the integrity of this process, the XMO2 should be
recalibrated periodically. This is typically done every 1-3 months
with a single (offset) calibration gas, depending on the application.
The optimum recalibration interval depends on such factors as %O
2
range, required accuracy, components of the gas mixture, the
cleanliness of the sample gas, etc. In addition, the XMO2 should be
recalibrated with the two-gas (zero gas and span gas) method at least
once per year. Again, the optimum calibration interval depends on the
specific application.
Using the calibration procedures in this chapter, the XMO2 can be
recalibrated for the same %O
2
range, background gas mixture, and
compensation signals used for the factory calibration. However, if it
has been some time since the original factory calibration, or if you
want to calibrate the XMO2 for a different %O
2
range, gas mixture,
or compensation signal, contact the factory for instructions.
Caution!
The calibration procedures described in this chapter
require the use of specialized apparatus and should be
performed only by properly trained service personnel,
following all applicable safety practices.