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4) Release both the CALIBRATE key and the ↓ key.
The unit will automatically enter the “LOCKED” condition and return to
normal operation.
2.2.4 Factors Influencing Calibration
The primary factors influencing the MAXO
2
analyzer are temperature,
pressure, and humidity.
Effects of Temperature
The MAXO2 analyzer will hold calibration and read correctly within ±3%
when in thermal equilibrium within the operating temperature range. The
device must be thermally stable when calibrated and allowed to thermally
stabilize after experiencing temperature changes before readings are
accurate. For these reasons, the following is recommended:
1) Allow adequate time for the sensor to equilibrate to a new ambient
temperature.
2) For best results, perform the calibration procedure at a temperature
close to the temperature where analysis will occur.
Pressure Effect
Readings from the MAXO2 analyzer are proportional to the partial
pressure of oxygen. The partial pressure of Oxygen (PO
2) is equal to the
percentage of oxygen (%O2) times the absolute pressure (AP) at which
the sample enviroment is measured. (PO2=%O2 x AP). Thus the readings
are proportional to the concentration if the pressure is held constant. Flow
rate of sample gas can affect pressure at the 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.
R213M15K.qxd 6/26/2006 8:59 AM Page 10