MaxTech MAXO2 OM-25ME - Manual (Page 18)

Pressure Effect
Readings from the MAXO
2
Monitor are proportional to the partial
pressure of oxygen. The partial pressure of Oxygen (PO
2
) is equal to the
percentage of oxygen (%O 2 ) times the absolute pressure (AP) at which
the sample enviroment is measured. (PO 2 =%O 2 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
Monitor 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
Monitor 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
Monitor 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, the following is recommended:
1) Avoid usage in environments greater than 95% relative humidity.
2) When used in a breathing circuit, place the sensor upstream of the
humidifier.
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