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6
sensor in that back pressure at the sensing point may change. For
these reasons, the following is recommended:
1. Calibrate the MAXO
2
®
analyzer at the same pressure as the
sample gas.
2. If sample gases flow through tubing, use the same apparatus and
flow rates when calibrating as when measuring.
3. The MAXO
2
®
analyzer oxygen sensor has been validated at
pressures up to 2 atmospheres absolute. Calibration or operation
above this pressure is beyond the intended use.
Humidity Effect
Humidity has no effect on the performance of the MAXO
2
®
analyzer
other than diluting the gas, as long as there is no condensation.
Depending on the humidity, the gas may be diluted by as much as
4%, which proportionally reduces the oxygen concentration from the
dry concentration. Environments where condensation may occur
are to be avoided since condensate may obstruct passage of gas
to the sensing surface, resulting in erroneous readings and slower
response time. For this reason avoid usage in environments greater
than 95% relative humidity.
3.0
OPERATING INSTRUCTIONS
To check the oxygen concentration of a sample gas: (after the unit has
been calibrated)
1. Connect the sample hose to the barbed fitting on the bottom of the unit.
2. Attach the other end of the sample hose to the sample gas source and
initiate flow of the sample to the unit at a rate of 1-5 liters per minute (2
liters per minute is recommended).
3. Using the ON/OFF key
, make sure the unit is in the power on
mode.
4. Allow the oxygen reading to stabilize. This will normally take about 30
seconds or more.
4.0
SENSOR REMOVAL AND REPLACEMENT
The OM-25A is shipped with a new MAX-250 oxygen sensor installed.
Although the sensor has a very long expected life, eventually the sensor
will require replacement. Removing or installing a sensor, when necessary,
is a very simple procedure. To remove and install a new
sensor:
1. With the front of the analyzer facing downward and the bottom facing
away from you, press down with both thumbs on the center of the battery
compartment cover and slide the cover off.