Startup & Operation 3-3
September 2007
Analog Output
Calibration Options
The XMO2 4-20 mA analog output has been calibrated at the factory
for the oxygen range indicated on the XMO2 Calibration Sheet
shipped with the unit. Upon initial startup, field verification and/or
calibration of the 4-20 mA analog output is required. To perform this
task, either of the following procedures may be used:
• pushbutton calibration (offset gas method)
• RS232 digital communication calibration (zero/span gas method)
After the XMO2 is in operation, field calibration is recommended at
intervals of about 1-3 months, depending on the application. Refer to
Chapter 4, Field Calibration, for additional information regarding the
field calibration of previously installed units.
Pushbutton Calibration Pushbutton Calibration is the simplest method for performing an
initial field calibration of the XMO2’s 4-20 mA analog output. This
method requires only a single calibration gas, called an offset gas.
The XMO2 is usually factory-programmed for the offset gas
pushbutton calibration method. The Calibration Sheet shipped with
your unit specifies the recommended oxygen level (in %O
2
) for the
offset gas to be used. This is the same offset gas oxygen level that was
used for the factory calibration. If no offset gas %O
2
is specified on
the XMO2 Calibration Sheet, the factory calibration was done with
100% N
2
(0.00 %O
2
) and the field calibration should use the same
offset gas.
To prepare for this calibration method, refer to Figure 3-1 on page 3-4
and perform the following preliminary steps:
1. Turn the power on and allow at least 30 minutes for the XMO2 to
reach temperature stability.
2. Loosen the set screw that locks the XMO2 cover in place, and
unscrew the cover.
IMPORTANT: Remember to replace the cover after the calibration
has been completed.
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