Hollis Explorer User Manual - page 47
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In general, Oxygen and CO
2
sensors do not drift excessively. Constant
calibration (every dive) is not required. Instead, frequently check sensors
for accuracy with a known gas (air) as previously described on the preced-
ing page. If possible keep sensors dry between dives, especially during
storage.
! WARNING: Performing calibration before every single dive may
mask other potential problems.
CONDUCTING AN O
2
SENSOR CALIBRATION
During the Pre-dive sequence you have the option to calibrate the oxygen
and CO
2
sensors from the Calibration screen. Selecting O
2
, will display
another series of screens that will guide you through the calibration. Please
see descriptions later in the manual for calibrating the optional CO
2
sensor.
SUMMARY OF DO’S AND DON’TS
OF OXYGEN SENSOR CALIBRATION
When calibrating sensors there are two factors that the EX-
PLORER takes into account:
1. Ambient pressure
2. Ambient AIR oxygen content
These two factors multiply to determine the partial pressure of
the oxygen exposed to the Oxygen sensor.
Example:
20.9% oxygen at 1000 mbar = 0.209 mbar partial pressure of
oxygen
20.9% oxygen at 750 mbar = 15.675 mbar partial pressure of
oxygen
The EXPLORER uses ambient air as the calibrating gas, because
its composition is accurately known. This is in contrast to say a
cylinder of compressed oxygen that can vary from supplier to
supplier, as well as around the world, from at least 94% to 100%.
3
.1
2