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3.12
To achieve a good calibration some basic rules must be observed:
1. The Oxygen sensors must be exposed to the pure calibrating
gas. So for an air calibration, the sensors must be flushed with
air. Just taking the hoses off is NOT sufficient, as pockets of gas
can be enveloping the sensors.
2. DO NOT execute calibrations to remedy a rebreather whose
PPO2 accuracy is drifting over short periods of time. Some other
problem is likely to be the cause in this instance. Possible causes
include:
• Oxygen sensors have become wet
• Current gas exposed to the Oxygen sensors is not what you
think it is.
• The mini-jack connection is corroded
Check the readings on the STATUS screen (average) or Service
Mode STATUS Screen (all 3 sensors).
If a sensor is reading incorrectly, first remove it and clean the
mini-jack connector. This can be done with Hollis approved electrical contact cleaner or simply by wiping the connector with
a lint free cloth. DO NOT scratch the connector with a metal
instrument. Then look for droplets of moisture on the sensor
membrane. Use a rolled tissue to gently wick any moisture droplets from the sensor WITHOUT making contact with the sensor
membrane itself. Pushing on the sensor membrane face can
destroy the sensor.
If neither of these corrects the reading, then the sensor should
be replaced.
The Oxygen sensors vary only slightly over time. Temperature,
atmospheric pressure and moisture have far greater short-term
effects on the readings. Calibrations carried out once a week
should be more than sufficient, unless the EXPLORER has been
transported to different climates or significantly different ambient conditions.
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