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Portable Oxygen Monitor Service Manual
Teledyne Analytical Instruments 35
functional at this point. After calibration is completed, the alarm set
points will need to be reset.
To calibrate the instrument refer back to Section 2.1.3.
3.6 Alarms
To set the alarms on the MX300-I monitor, refer to Section 2.1.4.
3.7 Gas Sampling
3.7.1 Humidity
Humidity does not directly affect the accuracy of the sensor's
measurement. However, when a nebulizer or other device is used to
increase moisture levels in gas mixtures, the moisture actually dilutes
the mixture. This dilution effect decreases the oxygen concentration.
For example, if an 80% oxygen gas mixture is humidified to
saturation at room temperature, the resulting gas mixture will contain
only 77.5% oxygen. Your portable oxygen monitor accurately measures
decreases in the oxygen concentration due to the dilution effects of
moisture added to gas mixtures.
As with all oxygen sensors, excessive condensation on the sensing
surface of the R17MED will block the diffusion of oxygen to the sensor,
rendering it inoperative. We recommend installing the sensor on the dry
side of the breathing circuit at all times.
3.7.2 Temperature
The R17MED oxygen sensor adjusts for ambient temperature
changes in the range of 0–40°C (32–106°F). Since the thermistor that
compensates for these changes is located in the rear of the sensor
assembly, it is important that gas mixtures, flowing over the front of the
sensor, be at room temperature. Reading errors may occur if hot gases
from a heated humidifier are directed past a sensor teed into a breathing
circuit.
A small thermal tracking error may be encountered in application
areas where the entire sensor assembly is placed in the gas mixture to be
analyzed (e.g., incubators). Holding the sensor in your hand for more
than a few minutes can also affect the temperature tracking which
appears as a slow drift on the LCD. No adjustments should be made